If you don’t have access to this article, then I recommend, highly recommend, that you access Dr. Romero’s dissertation. It’s publicly available and an awesome read.

Some time ago, very briefly, we mentioned the phases of host-seeking in blood-sucking insects described by Lehane. Another author has proposed some reorderings and extensions as follows (Lazzari 2009):

1. activation
2. appetitive search
3. host detection
4. host finding
5. host contact
6. host biting
7. food recognition and feeding
8. leaving the host

Quite the long list of things to investigate in the bed bug? (And of tasks for the bed bug itself.) But we can try to understand what is being discovered and place what came before in some context, if possible — though Mellanby’s bed bugs, rooming as they were with rats, very efficient predators of bed bugs those rats!, may give us some trouble. And, by the way, aren’t rats themselves nocturnal? How would that fit in?

Regarding the first step, Lazzari says simply: “When hosts are less active or the environmental conditions become adequate for food search, the insects start moving spontaneously.” Before coming into contact with or indeed searching for host cues. This spontaneous activity may be, and I think usually is, controlled by an internal clock. Many other processes, like mating, laying and emerging from eggs, emerging from nymphal stages, indeed the time of day when an insect is more or less sensitive to odors, may be controlled by internal clocks (Lazzari and Insausti 2008). And these clocks can synchronize with external cues, such as the daily cycles of light and temperature. Adjustable internal clocks seem convenient for the enterprise of living, making it possible to anticipate changes, learn and adapt.

For circadian terms, I have been relying on this Dictionary of Circadian Physiology which you may also find very useful:

The zeitgeber [synchronizing stimulus] “gives” the local time, not the ability to keep time (which the organism already possesses).

Back then to Romero et al. 2010:

Evidence of endogenous rhythms of activity is revealed when the animal is experimentally exposed to contstant dark (DD), or constant light (LL), where temperature and any possible external factor (Zeitgeber) are kept constant (Aschoff, 1960).

The insects used in this study were female and male adults and 5th instar nymphs. Three nutritional states were examined: unfed for one week (adults and 5th instars), unfed for five weeks (adults and 5th instars), and recently fed (2 days before) adults.

The method of this study is very interesting, digital photographs. Thousands of photographs taken at 10-minute intervals were examined and the positional changes of the bed bug recorded. A minimum of 864 photos per bed bug, 12 bed bugs per experimental group.

Findings

Bed bugs are nocturnal! (But this wouldn’t be about bed bugs if there weren’t some rather tricky and enigmatic aspects.)

Most movement (more than 80% of recorded positional changes for adults and more than 60% for nymphs regardless of nutritional state) occurs in the dark segment of a 24-hr light-dark cycle of 14 hours of light followed by 10 hours of dark, 14:10 L:D. This dark segment is called the scotophase, but we will call it night where possible here. Movement begins soon after lights-off, continues and remains high for several hours, and then declines in the last third of the night. Onset of activity is about 2 hours into the night. There are gender and nutritional state differences in the offset of activity, with females stopping movements later in the night (8.3 ± 0.14 h) than males (7.9 ± 0.14 h), and 1-week-unfed adults stopping later (8.7 ± 0.14 h) than 5-week-unfed adults (7.5 ± 0.18 h) or 2-days-recently-fed adults (8.1 ± 0.17).

The study further shows that bed bugs have an internally controlled rhythm of activity that persists under conditions of constant dark (DD) or constant light (LL) for 4 days. Thereafter “the rhythms were disrupted in DD and became less distinct in LL.”

If the dark segment of the light-dark cycle is extended 12 hours, bed bugs gradually shift their activity to the new “night” and require four days to recover to previous peaks of activity.

Based on the discussion of peak activity recovery after a phase shift, if I understand correctly, the night-time peaks of activity (in the dark segment of a 12:12 L:D cycle) were 6.2h [5.1–7.3] for females and 6.3 h [5.3–7.4] for males.

And this is very interesting, a burst of activity occurs shortly after lights-on:

In the transition from dark to light, most of the insects showed a sudden increase in activity, but the frequency of movements rapidly decreased, persisting at low levels throughout the photophase [...] Half of the photophase movements in all groups occurred 1 h after lights-on.

The authors suggest two possible explanations: “an excitatory reaction of bed bugs caused by the lights-on transitional signal (Aboul-Nasr and Erakey, 1968)” or else the lights-on signal may be “an indication to wandering bed bugs that it is time to return to the less exposed harborages.”

Note that each bed bug in the experimental chamber rested on filter paper inside a petri dish, thus exposed and not in a refugium.

As for the relative movement of female vs male and fed vs unfed bed bugs:

Adults held unfed for one week (averaging females and males) moved 18% more often than those unfed for five weeks (36.0 and 25.1 positional changes per day, respectively) (t = 3.5; df = 78; P < 0.05) and 22% more than adults that had fed (36.0 and 23.0, respectively) (t = 4.3; df = 77; P < 0.05) (Fig. 6). There was no significant difference in the number of positional changes between adults held unfed for five weeks and those that had fed (t = 0.77; df = 78; P = 0.72). Overall, females changed position significantly more than males (30.4 and 25.5 movements per day, respectively) (F = 3.9; df = 1, 78; P < 0.05).

Finally, the pattern of activity over time (6 days) [you can see these fluctuation charts on page 45 (Romero 2009), and indeed all the other charts] is described thus:

Adults that had fed showed a different daily fluctuation in the pattern of movements (Fig. 7A). By day three, males had increased movements with respect to day one by 61%, but female movement only increased 10% (Fig. 7A). However, after day three, males moved gradually less until the end of the experiment at day six, reaching levels similar to those recorded on day one. In contrast, females increased their activity only after day three until day six, having an increase of 46% at this time compared to movements recorded on day one. Adults held unfed for one week showed a marked fluctuation in daily activity over the six days of recording (Fig. 7B). By the third day, bed bugs from this group had increased their spontaneous activity by 21 and 30% (females and males, respectively), in relation to the first day. After day three the number of movements of both groups gradually decreased. By the end of the recording period, females and males from this group reduced daily movements by 18 and 13%, respectively, in relation to day one, and 32 and 33% from their respective activity peak (Fig. 7B). A less pronounced fluctuation of activity was displayed by bed bugs held unfed for five weeks (Fig. 7C). During the first days, the activity of females and males remained relatively stable; then after day three, the daily rate of movements began to decrease until the end of the experiment. Females and males from this group reduced the overall number of daily movements by 33 and 29%, respectively, in relation to day one (Fig. 7C).

Questions!

First the obligatory question about what this could mean for dispersal, as we have been wondering forever. Not sure why I even expect new information to shed light on this question, seems the most difficult one, just being hopeful and wondering. So: if 5 weeks of starvation are enough to make bed bugs a bit conservative in their spontaneous activity, then who are the dispersers, if there is such a word, the bed bugs that will move long distances in search of a host (instead of giving up? or remaining where they are?), and what possible combination of nutritional, environmental or conspecific cues make them go? Obviously, more research is needed.

More related to what we have reviewed in the previous two posts, you may well be thinking that none of this described so far (actually, that’s not quite right, none of it except for the nocturnal part and the suggested relationship between nutritional state and activity) is very congruent with what Mellanby observed, or rather concluded from his trap catches.

What to make of this?

Regarding the differences between their findings and Mellanby’s, the authors cite the difference in methodology, as their experiments were conducted under controlled conditions without a host, and Mellanby’s was based on passive trap catches, and further, the recurring appearance of someone checking the traps every 3 hours which could have disturbed the normal pattern of activity.

But this isn’t very satisfying, isn’t it? Because if Mellanby’s peak trap catch was not a measurement of peak activity of bed bugs, what was it a measurement of?

So much work has to be done. But indeed who will look at 864 photographs of each bed bug or perform similar feats!

Just to look at some complexities and interactions that may (or may not!) be studied later in the bed bug, consider that in another blood-sucking insect, Triatoma infestans (the kissing bug), there are two peaks of locomotor activity in what is called a bimodal circadian rhythm. One occurs early in the night and is associated with host-seeking and the second peak occurs before dawn and is associated with refuge-seeking (Lorenzo and Lazzari 1998). T. infestans actually remains outside its harborage in the intervening hours between the two peaks, “performing a copious diuresis” (Lorenzo 1997, cited in Lorenzo Figueiras and Lazzari 2000). T. infestans is not attracted by the fresh fecal traces of conspecifics and does not assemble on fecal “footprints” until 8-10 hours hours have passed from its blood meal (Lorenzo Figueiras and Lazzari 2000). An investigation into the temporal change of the aggregation response yielded the insight that peak aggregation (insects clustered together with other insects) occurs just before sunrise (Minoli et al. 2007).

Reading about triatomines is enormously interesting even if there are seemingly many important differences between them and old Cimex l.

What do you think? Were Mellanby’s bed bugs exhibiting a marked aggregation response at a certain time, confusing a trap for refuge? Something to think about when considering Mellanby’s traps or useless spitballing? I confess I’m slightly confused, and therefore reaching.

References:

Lazzari, Claudio R. 2009. Orientation Towards Hosts in Haematophagous Insects: An Integrative Perspective. Advances in Insect Physiology 37: 1-58. doi:10.1016/S0065-2806(09)37001-0

Lazzari, C.R. and Insausti, T.C. 2008. Circadian rhythms in insects, In: M.L. Fajul-Moles & R. Aguilar-Roblero (eds.) Comparative aspects of circadian rhythms. Research Signpost (ISBN 978-81-7895-329-8). [PDF available here]

Lorenzo, Marcelo G., and Claudio R. Lazzari. 1998. Activity pattern in relation to refuge exploitation and feeding in Triatoma infestans (Hemiptera: Reduviidae). Acta Tropica 70: 163-170. doi:10.1016/S0001-706X(98)00025-4.

Lorenzo Figueiras, A N, and C R Lazzari. 2000. Temporal change of the aggregation response in Triatoma infestans. Memórias Do Instituto Oswaldo Cruz 95: 889-892. doi:10.1590/S0074-02762000000600026

Mellanby, Kenneth. 1939. The Physiology and Activity of the Bed-Bug (Cimex Lectularius L.) in a Natural Infestation. Parasitology 31: 200-211. doi:10.1017/S0031182000012762.  

Mellanby, Kenneth. 1940. Rhythmic Activity in Domestic Insects. Acta Medica Scandinavica 103: 89-98. doi:10.1111/j.0954-6820.1940.tb11083.x

Minoli, S A, S Baraballe, and A N Lorenzo Figueiras. 2007. Daily rhythm of aggregation in the haematophagous bug Triatoma infestans (Heteroptera: Reduviidae). Memórias Do Instituto Oswaldo Cruz 102: 449-454. doi:10.1590/S0074-02762007005000033

Romero, Alvaro. 2009. Biology and Management of the Bed Bug, Cimex lectularius L. (Heteroptera: Cimicidae). Ph.D. dissertation, University of Kentucky. http://archive.uky.edu/handle/10225/1119

Romero, Alvaro, Michael F Potter, and Kenneth F Haynes. 2010. Circadian rhythm of spontaneous locomotor activity in the bed bug, Cimex lectularius L. Journal of Insect Physiology 56: 1516-1522. doi:10.1016/j.jinsphys.2010.04.025.  

These traps are circular, 22 cms in diameter at the base, with sides sloping gradually towards the center where there is a circular opening 11 cms in diameter and 4.5 cms above the base. The sides are roughened on the outside to give a grip to insects’ feet. The hole at the top is partly covered over with metal vanes which tip over when a cockroach stands on them, and so the insect falls inside the trap. There is a small container for “bait” (a mixture of beer and banana is advised) in the middle, and the insects are supposed to fall into the trap as they try to reach the bait. Once in the trap they cannot climb out. Actually an unbaited trap was found to catch as many cockroaches as a baited, and no bait was used. The traps are not intended for catching bed-bugs, but they do catch them, and any other insects which are running about; beetles, spiders and woodlice have been also captured.

Mellanby, Kenneth. 1940. Rhythmic Activity in Domestic Insects. Acta Medica Scandinavica 103: 89-98. doi:10.1111/j.0954-6820.1940.tb11083.x

This really is impossible, isn’t it? How can such a trap work for bed bugs? What do you think?

Can bed bugs crawl on a concave surface? Let’s say that they can’t (I don’t know, do you?) — why would they drop into the trap in the first place?

I don’t want to get ahead of myself too much but here are some possibilities that occur to me (if you find them wanting, consider the source!):

• Perhaps in a heavy infestation practically anything will catch bed bugs — as long as they can climb it — and will trap them as long as they cannot crawl out
• Perhaps the traps, while not baited for either pest, did in fact attract bed bugs. How could they possibly? By preserving in them the smell of their buddies, their conspecifics?

By now surely you’ve taken a peek at the photo below and my surprise is no more. Let me tell you briefly how difficult it was to find the Demon cockroach trap that Mellanby used in his natural infestation in the rat room, the Demon cockroach trap used in Britain for many decades it seems, a trap that must have been so common, he felt no need to describe it until he presented his paper in another country. Extremely difficult.

Because it wasn’t called a Demon cockroach trap! Mellanby probably couldn’t bring himself to call it by its common name. Maybe because it’s totally wrong and silly.

It was called a Demon beetle trap.

My aim is to not acquire any more pest “interests” in this lifetime but even I know that is just wrong. Designed to mess with us seventy years later?

Beetle as a gentler, inoffensive word for cockroach, I just didn’t know. I would still be a bit unsure that this is in fact a case of euphemism, as opposed to say, a case of a product used for several pests, but there is Mellanby being super clear as always. (And I have since learned that if I listened to Kanye West I would have figured this out much sooner.)

So here is your Demon beetle trap:

Demon cockroach trap

In a nice historical rhyme, the eBay seller of this trap happens to be in a certain town in South Yorkshire.

And here is a really fabulous advertisement page from a G. Harding & Sons catalogue, dated March 6, 1901. The most successful Trap yet introduced.

The third installment of this series is a bit more involved, but I am hoping it will automagically appear on this page sometime this weekend. Until then, very best wishes for the new year. I wish that you will be hopeful about the future, about our bed bug (to use a gentler word) situation.

This process is slow and apparently fraught with failure, but what is being learned is there for us to read and understand if only we can get past the language and shorthand that are not meant for us — and in most cases there is in fact no other way to access this information. This is not a simple matter and is, for me at least, a constant struggle.

The goal of today’s exercise is to understand this paper: Romero et al. 2010. Circadian rhythm of spontaneous locomotor activity in the bed bug, Cimex lectularius L. Journal of Insect Physiology doi:10.1016/j.jinsphys.2010.04.025.

But I can’t get there from here, not without a lot of other reading first.

So then, should we begin with the classical study?

Sometime in 1938, Kenneth Mellanby¹ discovered an infestation of bed bugs in rat cages at the University of Sheffield. What the rats were being used for he does not say. The infestation had existed for several years.

He did quite a lot with his good fortune, as we’ll see.

The little field work which has previously been carried out on the bed-bug has consisted of examinations of insects which have been discovered and removed from their hiding places. Useful as such results may sometimes be, they give little information about the normal activities of the insects.

I have been able to trap bed-bugs which have left their hiding places voluntarily during their periods of normal activity. Examinations of these insects tell us a good deal about their habits.

Does he sound pleased with himself or what?

Mellanby, Kenneth. 1939. The Physiology and Activity of the Bed-Bug (Cimex Lectularius L.) in a Natural Infestation. Parasitology 31: 200-211. doi:10.1017/S0031182000012762.

There was a lot going on in this rat room. For one thing, there were cockroaches there which he also took the opportunity to study, but Mellanby believed that they were not interested in the bed bugs (and references another study to that effect).

As one would expect, the rats in this room ate some of the bed bugs!² But not too many of them, or not as many as they would in labs where Mellanby had previously found that “nearly all the bugs are eaten and very few feed and survive.” The difference consisted apparently in the number of rats occupying a cage. When “two rats tended to curl up together and sleep” the bugs were ignored and therefore more successful.

The room was 4 by 3.5 meters and 3.5 meters high. Two meters above the floor there were three windows, but there was no direct sunlight. The rats were in cages on iron racks covering the walls up to the windows. The temperature in the steam-heated room was somewhere between 20-27°C (68-80.6°F).

The floor was of concrete and the walls of smooth plaster, but cracks and particularly the spaces surrounding the pipes in the walls afforded shelter to the insects. Most of the bugs, however, seemed to lurk in the crevices in the metal cages containing the rats, and these animals seemed to form the only food supply for the bugs.

Mellanby collected bed bugs in this room by means of traps placed along the walls and in the middle of the room. I will have a great deal to say about this “Demon” cockroach trap but for now let’s just see what he says of them:

Two kinds of traps have been used, “Demon” cockroach traps and rolls of corrugated paper. In each experiment four “Demon” traps were placed, each one always on the same spot on the floor of the rat room. The bugs in their wanderings climbed up the sides of the traps, fell in and appeared to be unable to climb out again. All stages of nymphs as well as adults were caught by this method. In the second method small rolls of corrugated paper were left on the floor of the room, each roll consisting of a cylinder of paper 10 cm. long and 4 cm. in diameter; the bugs found hiding places in the folds of the paper.

So, yes. What in the world is a Demon cockroach trap and how came it to trap so many bed bugs? I am relieved that after a long, frustrating search I will be able to answer the first part of that question, in good time.

The principal difference in the catches made by the two methods of trapping is that 77.9% of the bugs caught in the “Demon” traps were unfed, whereas only 18.1% of those found in the corrugated paper were unfed. The reason for this is easily seen. Once a bug was inside a “Demon” trap, it was unable to escape, but when a bug crawled inside a roll of corrugated paper it could as easily crawl out again. Hungry bugs seeking food would not remain in the paper, but fed individuals would find a snug hiding place.

This is extremely interesting and here Mellanby makes certain assumptions that we should pay attention to:

It is probable that the “Demon” traps caught such a small proportion of fed bugs because many newly gorged individuals, being less agile after having ingested a considerable weight of blood, tend to remain near the cages in which they have fed. Evidence given later indicates that practically all the unfed bugs captured in the “Demon” traps were hungry individuals which had left their hiding places to seek for food.

I honestly don’t understand the “evidence given later” which seems to hinge on the egg production of females during the first two days after capture (60% of them laid eggs). (My copy of this article is annotated by a previous reader and he or she marked this section just as I would have.)

I’m not sure what to make of this and I wish I could talk to my fellow reader (across how many years?) who also marked the above section with an arrow and, I imagine, understood it perfectly.

This, by the way, is the study that allowed Mellanby to calculate the time between feedings (he painted individual bed bugs and recaptured them, a whole interesting subject in itself), at approximately 6 days. [Update 1/8/11: I made an interesting mistake here (and also here). Or, put another way, recaptures may indeed be fascinating, but this is not really how Mellanby derived his conclusions about the time between feedings. I will correct this as soon as I can.]³ For a modern research update on feeding intervals, see this.

Peak catch

On four nights in May 1938, Demon traps were examined every 3 hours each night. Each removal took less than 5 minutes and the light was not turned on. Still, Mellanby reports that during the day the bugs’ behavior was inhibited by workers entering the rat room, but that this did not seem to happen at night, as long as a light was not turned on, based on the numbers of bed bugs caught on nights when no one entered the room.

The maximum catch was obtained at the same time each night. Each point in the graph indicates the number of bugs collected during a period of 3 hr., and the times marked on the abscissa indicate the middle of each period. Thus 0130 represents the collection made between midnight and 3 a.m. It appears that the bugs were most active after 3 a.m. During most of this period the room was not dark, for the sun rose shortly after 4 a.m.

Activity of bed bugs in rat room. May 1938. K. Mellanby (1939) The Physiology and Activity of the Bed-Bug ( Cimex Lectularius L.) in a Natural Infestation.

This means that most bed bugs were caught in Mellanby’s traps sometime between 3 a.m. and 6 a.m. — with the sun rising after 4 (GMT+1, British Summer Time).

Hmmm!

Daytime activity and artificial light

Though in May the bugs were mostly active at, and after, dawn, the presence of a 60 W. electric lamp left burning all night affected the catch considerably. At this time of year the electric light would give greater illumination than daylight in the animal room until about 5:30 a.m., after which daylight would be the brighter.

On two nights when the lamp was left burning, the trap catch was greatly reduced to 24 bed bugs from a high of 65 when no light was left on.

Bed bugs were routinely caught during the day as well as night.

Several catches were made between 9 a.m. and 6 p.m.; on several weekdays no bugs or only one were caught, but on Sundays when the room was not entered all day as many as nineteen bugs were caught. This was during the part of May 1938 when the average nightly catch was sixty-five.

Complete darkness

On one occasion the animal room was kept in complete darkness for a period of 45 hr., from midday on Saturday until Monday morning. The traps were examined throughout the whole period at 3-hourly intervals. The darkness during the day did not in any way upset the rhythm of the bug’s activity, for catches made during the day and night were indistinguishable from those made under natural conditions of daylight and darkness.

___________________________________

1. Mellanby is an interesting figure and you can get an idea of the breadth and impact of his work in this obituary.
2. Are humans the only chumps who do not go in for Eat or Be Eaten when it comes to bed bugs? I know, but medicinal uses are not quite the same thing! We’re clearly talking bloody, real-time combat here.
3. In this article he also delves into his findings of the effect of movement on starved bed bugs (they lose weight at a significantly faster rate after 5 minutes of activity). Previously mentioned here. More Mellanby here (though not a particularly pleasant subject, if you take that as warning).

bed bug on servosphere - photo: Vincent Harraca

Ever since seeing this photograph of Vincent Harraca’s research at Lund University (Sweden) I have been looking forward to learning more.

This year Dr. Harraca and his colleagues published two deeply interesting articles about the olfactory physiology of the bed bug and the interplay of chemical signals in bed bug mating. Male bed bugs approach recently fed bed bugs of either sex, but they quickly dismount males and large nymphs. This observation, building on recent investigations, led to a valuable mating-disruption experiment.

But I also wanted to ask about the impetus for bed bug research projects—as we learn more about the bed bug, we see more clearly how much is still unknown.

Dr. Harraca generously took the time to answer my questions via email, from South Africa where he is now researching an entomopathogenic fungus against an agricultural pest.

NYvsBB: I am excited by what feels like rushing advancement in our understanding of how bed bugs perceive odors from hosts and from other bed bugs and how they may interpret those cues and signals, to get what they want and where they’re going. It seems that your and other research teams have begun to fill in the physiology and behavior gaps. To an observer it seems like rapid progress. Although of course the gaps also seem large. But just in the past year you’ve described the olfactory system of the bed bug, two previously unreported nymph-specific chemical compounds were identified (Feldlaufer et al. 2010), and you and your colleagues devised a behavioral experiment that neatly exploits all this new knowledge.

But I confess I am impatient for the research that would eventually describe in all its complex detail how bed bugs find and access their hosts for a blood meal. So perhaps that is my first question, do you think signalling between bed bugs is more relevant for control efforts and that has made it a priority for investigation?

Vincent Harraca: As you said, we started to fill in the gaps about bed bug physiology and behaviour. However, as most of the research is done by Universities, the focus is most of the time centred on theoretical questions with the aim to improve our general knowledge. Indeed, even if we keep in mind that our results may have a practical output, the information we gain is generally not directly applicable. Of course, it is because bed bugs started to be a problem recognised by the public opinion that academic researchers managed to get grants in order to develop our knowledge about this re-invading pest. Chemical ecology is one of the academic fields which gives the most “visible” results, because olfaction is the major sense used by most insects to orientate and the understanding of their perception permits to modify their behaviour.

NYvsBB: Before we get to your exciting investigation into the disruption of bed bug mating, can I ask about their antennae, the site of all the olfactory action? What are the sensilla for and how do they work? And how did you achieve electrical measurements on such small sites? Did you identify chemical compounds that seem like good candidates for further investigation of their role in bed bug orientation and host-seeking?

Vincent Harraca: An odour is composed by a specific blend of different molecules and it is the perception of some of these molecules by olfactory receptor neurons which is called olfaction. When the adequate odorant molecules bind the adequate neurons, an electrical signal is created and transmitted to the brain. In the insects, these neurons are housed inside sensilla (evaginations of the cuticle looking like hairs) mostly placed on their antennae.

bed bug antennal sensilla: trichoid sensilla (hairs) (E), smooth peg sensilla (D), and grooved peg sensilla (C) - SEM image: Vincent Harraca

Scientists have developed different electrophysiology techniques in order to measure this electrical signal produced after stimulating the neuron with chosen odours. We applied the technique of single sensillum recording on bed bugs and demonstrated some of the compounds bed bugs are able to smell or not (Harraca et al. 2010a). The main conclusion of our study is that compared to other blood feeding insects such as mosquitoes, bed bugs detect fewer compounds, meaning they might mostly rely on other cues than odours to find us. It is also perhaps for this reason that most of the published laboratory experiments (meaning with positive results!) on bed bugs have focused on the detection of their refuge or their interactions with other bed bugs (Levinson & Bar Ilan 1971, Siljander et al. 2008, Olson et al. 2009, Harraca et al. 2010b, Weeks et al. 2010…). In parallel to that, the few studies which have tried to add odorant molecules to traps in order to enhance their attraction failed (Anderson et al. 2009, Wang et al. 2009), but it was mostly because they used mosquito attractant molecules that we showed bed bugs cannot smell (Harraca et al. 2010a). This latest example demonstrated the value of basic theoretical knowledge before application.

NYvsBB: The very small number of odors that bed bugs actually perceive, or respond to, seems significant. Smaller than triatomines. What are odors derived from, excretions from hosts?

Vincent Harraca: Fragmented studies about blood feeding insects seem to demonstrate that they use a combination of compounds from different origin. Some are more associated to the host (i.e. carbon dioxide from the breath, carboxylic acids and octenol from the skin, phenols evacuated via urine) whereas other molecules (such as terpens or ammonia) are more linked to refuge. It is based on this knowledge that the first traps baited with odours were made (Anderson et al. 2009, Wang et al. 2009). Unfortunately, as the olfactory perception of the bed bug seems to be much narrower than other vectors (Harraca et al. 2010a), they do not smell compounds such as lactic acid or octenol used in these studies and which are quite efficient to attract mosquitoes. Until now, CO2 and heat were the only host cues proven to enhance attraction of bed bugs to traps.

NYvsBB: I am thinking of the servosphere experiments I was so looking forward to learning more about—can you tell us about them?

servosphere - photo: Vincent Harraca

Vincent Harraca: Before applying a new technology it is always good to test it in a laboratory controlled environment. But once more, doing behavioural experiments with bed bugs is not straightforward. Indeed, during experiments with arena they mostly followed the wall and scarcely adventure in open areas. For these reasons, many studies only measured the resting position of the bed bug, which in my opinion has no meaning except when looking for refuge cue. In order to see direct behavioural effect (such as seeking for a host?!), we tried to develop experiments on a servosphere (locomotion compensator) which proved to be quite helpful in studying the behaviour of other walking insects (Otálora-Luna et al. 2004…). Indeed, in this system the animal is totally free of movement and never encounters any boundary. Moreover precise information about his displacement (speed, direction, time of walking…) are recorded.

However, we quickly discovered that bed bugs hate moving air which is needed to release the odour to test. So during our experiments with this system, the bed bug systematically walked downwind without any visible difference linked to stimuli.

bed bug tracks recorded with servosphere - Vincent Harraca

That is why we returned to an arena behavioural experiment, but we tried to make it reflect as much as possible the bed bug natural environment and to measure precise behavioural parameters.

In our latest publication with bed bugs (Harraca et al. 2010b), we demonstrated the effect of two molecules that are exclusively emitted by the nymphs (Feldlaufer et al. 2010, Liedtke et al. submitted). The conclusion of this study is that young bed bugs are able to emit two molecules that identify their status and permit them to avoid the traumatic insemination by males. Indeed, when these molecules are emitted the males do not pierce the abdomen or inject any sperm to their partner.

NYvsBB: Where do you think this line of inquiry can take us?

Vincent Harraca: We do not know what could be the effect of introducing such compounds in a bed bug colony, but two scenarios may be possible: it decreases the reproduction rate (as the males think all the females are too young), or it increases the mortality rate of young bed bugs (because the males lose the ability to recognise them and pierce their abdomen while trying to fertilise them). In both situations, there could not be appearance of resistance (as the molecules used are produced by the bed bugs themselves) and this technique will allow a less rapid recovery of the colony after treatment and so, a quicker elimination. I unfortunately do not think these molecules employed on their own will be sufficient on short term eradication and they will have to be coupled to other techniques such as trapping. However, such odorant compounds may also have a repellent effect on the establishment of new colonies.

References:

Anderson, J F, F J Ferrandino, S McKnight, J Nolen, and J Miller. 2009. A carbon dioxide, heat and chemical lure trap for the bedbug, Cimex lectularius. Medical and Veterinary Entomology 23: 99-105. doi:10.1111/j.1365-2915.2008.00790.x.

Feldlaufer, Mark F., Michael J. Domingue, Kamlesh R. Chauhan, and Jeffrey R. Aldrich. 2010. 4-Oxo-Aldehydes from the Dorsal Abdominal Glands of the Bed Bug (Hemiptera: Cimicidae). Journal of Medical Entomology 47: 140-143. doi:10.1603/ME09210. [download PDF here]

Harraca, Vincent, Rickard Ignell, Christer Löfstedt, and Camilla Ryne. 2010a. Characterization of the Antennal Olfactory System of the Bed Bug (Cimex lectularius). Chemical Senses 35: 195-204. doi:10.1093/chemse/bjp096.  

Harraca, Vincent, Camilla Ryne, and Rickard Ignell. 2010b. Nymphs of the common bed bug (Cimex lectularius) produce anti-aphrodisiac defence against conspecific males. BMC Biology 8: 121. doi:10.1186/1741-7007-8-121. [open access]

Levinson, H. Z., and Anna R. Bar Ilan. 1971. Assembling and alerting scents produced by the bedbug Cimex lectularius L. Experientia 27: 102-103. doi:10.1007/BF02137766. [PDF available]

Olson, J.F., R.D. Moon, and S.A. Kells. 2009. Off-host aggregation behavior and sensory basis of arrestment by Cimex lectularius (Heteroptera: Cimicidae). Journal of Insect Physiology 55: 580-587. doi:10.1016/j.jinsphys.2009.03.001.

Otálora-Luna, Fernando, Jean-Luc Perret, and Patrick Guerin. 2004. Appetence behaviours of the triatomine bug Rhodnius prolixus on a servosphere in response to the host metabolites carbon dioxide and ammonia. Journal of Comparative Physiology A 190: 847-854. doi:10.1007/s00359-004-0540-5.  

Siljander, Eric, Regine Gries, Grigori Khaskin, and Gerhard Gries. 2008. Identification of the airborne aggregation pheromone of the common bed bug, Cimex lectularius. Journal of Chemical Ecology 34: 708-718. doi:10.1007/s10886-008-9446-y.

Wang, Changlu, Timothy Gibb, Gary W. Bennett, and Susan McKnight. 2009. Bed Bug (Heteroptera: Cimicidae) Attraction to Pitfall Traps Baited with Carbon Dioxide, Heat, and Chemical Lure. Journal of Economic Entomology 102: 1580-1585. doi:10.1603/029.102.0423.

Weeks, E.N.I., J.G. Logan, S.A. Gezan, C.M. Woodcock, M.A. Birkett, J.A. Pickett, and M.M. Cameron. 2010. A Bioassay for Studying Behavioural Responses of the Common Bed Bug, Cimex Lectularius (Hemiptera: Cimicidae) to Bed Bug-Derived Volatiles. Bulletin of Entomological Research FirstView: 1-8. doi:10.1017/S0007485309990599.

Note: Some of these articles are also available at the Armed Forces Pest Management Board’s free online library.

Mankin, R. W., R. D. Hodges, H. T. Nagle, C. Schal, R. M. Pereira, and P. G. Koehler. 2010. Acoustic Indicators for Targeted Detection of Stored Product and Urban Insect Pests by Inexpensive Infrared, Acoustic, and Vibrational Detection of Movement. Journal of Economic Entomology 103: 1636-1646. doi:10.1603/EC10126. [download free PDF here]

They used infrared and vibration sensors and microphones and they were able to detect distinctive vibrations and sound in crawling bed bugs, except in instars 1-3, at which stages mostly wriggling or scraping could be detected. If I understand correctly, bed bugs scraped or shuffled more than they wriggled or crawled (in the arena).

I love reading articles (or trying to read very-difficult-to-read articles) for the snippets of bed bug behavior they contain. Notice the following difficulty presented by the bed bug:

Bioassays were conducted for 30-s periods, beginning when an insect initiated movement after transfer by forceps to the center of the arena. The B. germanica and S. paniceum usually escaped rapidly from an open arena, so the top was secured with plastic film after these insects were transferred. The insects were monitored with a video camera (model HDR-SR1, Sony, Tokyo, Japan) after transfer, and in initial studies, insects that did not move toward a sensor within 1 min after being placed in the arena were discarded and replaced, as well as those that were not detected by two or more sensors within 30 s. This procedure usually worked well for B. germanica, S. paniceum, and S. oryzae but resulted in failure of many tests with C. lectularius and T. castaneum, which often avoided the sensors or ceased movement for long periods. A revised procedure was implemented to reduce the number of failed tests by using a recording options feature of the SignalExpress software that triggered a 30-s period of recording beginning when the signal from any sensor exceeded a preset threshold.

Emphasis added.

By the way, there is a tantalizing reference here to death-feigning behavior by T. castaneum (the red flour beetle). One wonders if the bed bug partakes of such tricks…

I searched in vain for a sound file of old Cimex l. at Richard Mankin’s fantastic sound library, and then I forgot what I was looking for! Extremely cool.

One feels like shooting Dr. Feldlaufer, or whoever keeps this list, a friendly email. Then again, the word volunteer appears twice on the first page, maybe it’s best (kinder) to leave them alone. (On the list itself, briefly: I think a persistent blind spot is the social history of bed bugs. A few history sources would not be out of place, especially if the list is intended for a broader audience.)

What is the FBBWG doing, do you think?

Because you know what it sounds like from reading the intro to that list.

It sounds like they don’t got no money!

And with almost too easy a search, one can confirm that is about right (PDF).

And yet here is this radio interview today with EPA Office of Pesticide Programs Registration Division Director Lois Rossi:

The workgroup is currently working toward a researchers meeting to “identify the knowledge gaps that we have about bedbugs, about how to control them, about how they behave, about different techniques that work in controlling them, and the efficacy of tools that are already out there,” Rossi said.

The workgroup is also working as a whole to improve communication with the public and provide a one stop guide for information on bedbugs. There are many Websites and fact sheets floating around, Rossi said, so the group wants build a clearinghouse where “the public can go to one spot and get reliable information.”

Improved communications — desperately needed and one hopes not just in the form of another website — but the first thing. A national research agenda. Is that what she meant?

Perhaps an overly imaginative reading, since having one without actual money to set it in motion would be sad? I don’t think the Feds do that, sad, intentionally.

There’s a bit at the end in which Lois Rossi seems ever so not so slightly to wish to walk back that whole public health pest designation thing. I may be misreading that too.

So then, a “very annoying” “nuisance pest” that nevertheless apparently merits another federal bed bug summit to be held February 1-2, 2011.

In a section titled “Bed Bugs, People, and Politics,” Harold Harlan, Michael Potter, Stephen Kells, Susan Jones, Lou Sorkin, Mark Sheperdigian, Changlu Wang, and Dini Miller will… I’m not entirely sure. No doubt they will share what they’ve learned, but you don’t have to know anything to know that they won’t be candid about the real politics of bed bugs and the real problems caused by it. No one really does that.

Check out the title of Lou Sorkin’s presentation: CimEX and The City: Only in New York?

Sounds like a treat!

I also think that Mark Sheperdigian’s presentation has an excellent title: Arming an unarmed populace.

If only.

On with the science.

Metarhizium anisopliae

Do you remember the talk about fungus research last year?

Cimex lectularius L. (Cimicidae – Heteroptera) control using the entomopathogenic fungus Metarhizium anisopliae — Gale E. Ridge and Anuja Bharadwaj, Connecticut Agricultural Experiment Station:

Cimex lectularius L. adults were treated with the entomopathogenic fungus Metarhizium anisopliae. In the laboratory, male and female bed bugs were treated with a range of fungal concentrations and by different delivery methods. Mortality was influenced by fungal concentration and delivery method. Metarhizium anisopliae is considered safe to humans. This study indicates that M. anisopliae could be an effective biological control agent for C. lectularius.

Dr. Ridge! Questions, questions. How do these fungal biopesticides work and what are the challenges? They have been studied for malaria vector control. Here’s a recent study that found a strain of Metarhizium anisopliae to be promising for certain mosquitoes, Mnyone et al. 2009 Parasites & Vectors doi: 10.1186/1756-3305-2-59:

The long-standing barriers that have prevented the widespread uptake of biological control agents include low virulence and short-term residual activity. In order to overcome such barriers it is necessary to screen an array of fungal strains to identify those with the greatest potential for development.

The article above is open access; this one is not, but mentioning in case you unlike me have access: Thomas & Read 2007 Nature Reviews Microbiology doi: 10.1038/nrmicro1638.

Another dispersal teaser!

Population genetic structure within and among aggregations of bed bugs (Cimex lectularius) — Virna L. Saenz et al. — North Carolina State University:

[W]e present the preliminary results of a novel hierarchical analysis of bed bug population genetic structure, with specific focus on the genetic effects of both active (within-building) and passive (human-mediated) movement. Through the application of polymorphic species-specific molecular markers, we address five key questions regarding bed bug diversity and dispersal: 1) what does within-aggregation genetic diversity tell us about infestation dynamics?; 2) within multi-unit apartment buildings, are infestations founded by single, or multiple introduction events?; 3) once established within buildings, do bed bug infestations follow a predictable dispersal pathways [i.e. infestation of apartments vertically and horizontally adjacent to the primary site of infestation]?; 4) within cities, are infestations more genetically similar to each other than to those from alternate cities?; and 5) do major interstate highways represent corridors for the dispersal of infestations. Samples were collected from ten states along the eastern United States and ten individuals from each collection genotyped for between 10 and 15 microsatellite loci. Results will be discussed

Wow. Do they seriously already have answers to these questions? Ms. Saenz! (Here’s a nice story of collecting bed bugs — and getting bitten.)

I am very interested in these dispersal questions but obviously this larger research project at NCSU also threatens to answer all those difficult questions people want answered about why and how we came to be in this mess. I wonder if some of us will find the answers inconvenient when they come? It’s going to be interesting for sure.

More abstracts

Molecular analysis of NADPH-cytochrome P450 reductase in the bed bug, Cimex lectularius (Hemiptera: Cimicidae) — Fang Zhu et al. — University of Kentucky

Combining heat and dichlorvos to control bed bugs, Cimex lectularius — Margie Pfiester Lehnert et al. — University of Florida

Evaluations of pyrethroid susceptibility and the effects of insect growth regulators against the common bed bug, Cimex lectularius, in the laboratory — Sumiko R. De La Vega and William A. Donahue, Jr., Sierra Research Laboratories:

Three strains of C. lectularius were evaluated in this project – two field-collected strains (“Earl” and “Cincinnati”) and one laboratory strain (“Ft. Dix”). Life tables were constructed for length of embryo development, fecundity, hatch rates, and survivorship as well as feeding and behavioral differences. Efficacy evaluations were conducted in the laboratory for differences in susceptibility to direct applications of pyrethroid formulations. Various insect growth regulators were also evaluated by direct application to bed bug eggs and substrates for ovicidal potential and the subsequent effects on feeding and ecdysis in first instar nymphs which successfully completed eclosion.

Effect of ATP on engorging responses of the bed bug, Cimex lectularius L. — Alvaro Romero and Coby Schal, North Carolina State University

Bed bug, Cimex lectularius, sampling techniques — John F Anderson, Connecticut Agricultural Experiment Station

Bio-efficacy of commercial insecticides against bed bug (Cimex lectularius) — Hiroshi Okamoto et al. — Sumitomo Chemical Co., Ltd:

In the early 1990s, bed bug infestations began to be seen an increase across the nation. In Japan, the occurrence of bed bug is also increasing in hotels or apartment houses. In this study, we evaluated insecticidal activity of Pyrethroids, Organophosphates and Carbamate which are commercialized in Japanese market for controlling the bed bug. Most of the active ingredients are available in other countries. In topical application test and filter paper contact test, d-d-t cyphenothrin and fenitrothion showed high killing activity. In oil spray tests, imiprothrin showed the highest knock down activity. Therefore, the combination use of d-d-t cyphenothrin and imiprothrin or fenitrothion and imiprothrin might be effective in the bed bug control.

Resolving the roles of symbionts in the bed bug — Mark Goodman et al. — University of Kentucky

Time to aggregation in the common bed bug (Cimex lectularius L.) — Matthew Douglas Reis — Virginia Tech

Mathematical model: A new toll for understanding bed bug populations in U.S — Andrea M Polanco-Pinzon — Virginia Tech

Cuticular analysis of field collected bed bugs (Cimex lectularius L.) that are known to be pyrethroid resistant — Reina Koganemaru et al. — Virginia Tech and University of Florida

BCE Symposium–Cultural Adaptation and Deployment of Scientific Advances Pursuant to Bed Bug (Cimex lectularius) Elimination in the United States — of these, this is especially interesting:

The development of Phantom® termiticide-insecticide for bed bug control: A cooperative effort — Robert Hickman — BASF Pest Control Solutions

What are the obstacles to pesticides development? What helps and what hinders? Don’t we all want to know?

Engaging People from Diverse Fields in Urban IPM Programs — see especially:

Options for dealing with people who refuse to do their part in an IPM program — Jonathan Wild — Bed Bug Task Force, Housing Authority of Portland, Portland, OR

and

Options for people who can’t do their part in IPM — Christiana Bratiotis — School of Social Work, Boston University

Pretty neat, ESA.

Update, November 28, missed this:

Repellent products for bite-free sleep – a low-maintenance, minimal-chemical answer to the bed bug problem — Robin Todd — ICR Laboratories

Update, December 13:

Check out Jim “spideyjg” covering the presentations from San Diego.

The research is out and worth a close reading, not only because it is the anticipated report on the effectiveness of old dry residues of chlorfenapyr against bed bugs, a subject that sets off our collective anxieties about using pesticides preventatively, but it’s the first study of chlorfenapyr’s effectiveness against pyrethroid-resistant bed bugs.

Romero, Alvaro, Michael F Potter, and Kenneth F Haynes. 2010. Evaluation of chlorfenapyr for control of the bed bug, Cimex lectularius L. Pest Management Science. doi:10.1002/ps.2002

Chlorfenapyr is what is called a pro-insecticide in that it does not become active (toxic) until it is metabolized by the bed bug itself after absorption. It belongs to a class of pesticides called pyrroles.

It works on bed bugs as follows:

The active metabolite of chlorfenapyr (AC 303,268) inhibits the ion transport system of the respiratory chain in mitochondria, preventing the production of the energy molecule adenosine triphosphate (ATP), so leading to insect death.

Yes, but let’s not be deterred.

Cell energy being the operative concept, if one wanted a handy simplification (and one does!), it seems to me they get tired and then they die:

Typical symptoms of chlorfenapyr intoxication in bed bugs include sluggish movements, prostration and limited responses upon contact stimulus (Romero A, personal observation). Such symptoms may be less apparent in commercial practice, and users should understand that bed bugs treated with chlorfenapyr succumb more slowly compared with some other insecticides.

Thank you for that image, Dr. Romero.

This is unlike the nerve-acting pyrethroids which make bed bugs hyperactive.¹ Here let’s note for those who are just joining us that pyrethroid resistance is depressingly widespread (also see) and so much at the center of our troubles.

On this note, the authors raise our interest a bit:

It has been suggested that resistant arthropod populations with enhanced monooxygenase activity might have increased sensitivity to chlorfenapyr (a case of a phenomenon known as negative resistance), because pyrethroid resistance can be caused by detoxification by the same enzymes (P450 monooxygenases) that activate the pro-insecticide chlorfenapyr.

Only to pour cold water a sentence later:

In the present study, the similar rate of mortality caused by chlorfenapyr to all strains, regardless of their pyrethroid susceptibility status, suggests that the presence of pyrethroid resistance in bed bugs might not limit (or enhance) the effectiveness of chlorfenapyr.

If only pyrethroid resistance were good for something. But they found no evidence of this negative resistance (because it would be too cool for words and we should know by now such gifts are not allowed us in this great contest with our enemy).

Let’s get back to insect death, by all means.

Comparison of two chlorfenapyr formulations

Phantom is formulated chlorfenapyr and there is an aerosol and a liquid concentrate:²

Toxicity of chlorfenapyr formulations (Phantom aerosol and Phantom SC), Romero et al. (2010), Pest Management Science

Yes, the obnoxious CIN-1 strain.

It’s very interesting that the aerosol is faster as a dry residue as well.

Directly sprayed bed bugs (aerosol formulation)

Direct sprays with the aerosol caused 30% mortality to both pyrethroid-resistant strains within 4 h (data not shown) and about 50% mortality in 24 h. In contrast, direct sprays of the water-based formulation took at least 3 days (WOR-1) or 5 days (CIN-1) to cause 50% mortality. Direct sprays of the blank aerosol (formulation without chlorfenapyr) killed 25% of individuals within 4 h, which indicates that some formulation ingredients also have some contact activity. Insecticides that kill bed bugs upon contact are widely used by pest control companies because they can quickly suppress populations and provide some relief to their customers.

And:

Bed bugs from strains CIN-1 and WOR-1 showed no avoidance of surfaces treated with the chlorfenapyr aerosol.

No avoidance “presumably lessens the potential spread of bed bugs to adjoining areas.”

Dry residues (of liquid formulation)

The LT₅₀ of (time necessary to kill 50% of individuals) for CIN-1 bed bugs exposed to a 4-month-old dry residue deposit of Phantom (liquid formulation) was 4.6 days (and it was 4.8 days for fresh deposits), which means that the 4-month-old dry residue was just as toxic as a fresh deposit. The LT₉₀ was 8.8 days.

In other words, chlorfenapyr is that rare thing, an effective (if slower) residual pesticide against bed bugs. What challenges are tied to its slow action (continued feeding and egg-laying?) have to be set against, well, that it works.

The authors note the potential preventive value of these findings:

The ability of chlorfenapyr to remain effective over an extended period of time is encouraging because bed bugs that are not sprayed directly may still succumb after residing on treated surfaces. Most insecticides available today have limited potency as a dry deposit against pyrethroid-resistant bed bugs. Dry residual action of chlorfenapyr might also aid in preventing new infestations if likely areas of infestation are previously treated.

…but recommend further study of chlorfenapyr’s residual effectiveness on various surfaces³ and the “suitability of prophylactic applications” — which I’m afraid leaves us where we were, with the manufacturer recommending just such a course (PDF) and prudent people urging caution.

More research please.⁴

_____________________

This was almost the last planned post here but there will be one more. Thanks for reading. I keep a bed bug-related reading list you are welcome to follow if you are interested. Best wishes.

1. This (PDF, University of Maryland) is very useful to understand modes of action.
2. Labels and MSDS sheets here.
3. In my limited experience I can recall one article, Fletcher & Axtell 1993 (PDF), that examines the variability of performance of bed bug pesticides on different surfaces — we discussed it briefly here. One PMP I’ve talked to dismissed the need for this kind of study. Puzzling.
4. Interestingly, The Columbus Dispatch reported yesterday that researchers were conducting a four-house field trial of Phantom and Alpine dust in central Ohio.

But two years earlier Girault had published a major article about bed bugs followed by an extensive critical bibliography, likely the entire literature of bed bugs until that time, which unfortunately I haven’t found, though surely much of it is in Usinger… but I wonder if only the useful bits and not the outlandish stuff that one really wants to find. In any case, Girault wrote several articles on the bed bug. We have time for only one.

There is this remarkable passage you should see about his “very unpleasant experiences” during a summer spent in “a small town in Virginia” (Girault studied at Virginia Polytechnic):

The whole place was thoroughly infested, and it was not an uncommon thing to see mattresses and bed-slats turned out to air, which were literally white with the insect’s eggs. The writer’s room was as bad as the rest; the old-fashioned bedstead was full of them, while during the day scores of them could be detected hiding in the walls. The place was almost unbearable, for the insects were not satisfied in staying indoors, but were frequently found secreted in one’s clothes. One night, returning to the room from outside, two were found beneath the collar, while occasionally, one would be found hiding within a pamphlet which was carried in my pocket. Wherever they were very numerous, many could be found frequenting privy-houses or other similar places, where they would be sure to obtain an occasional meal, visiting the host at every chance, night or day. That these insects are very active and freely move from place to place, that is to say, not necessarily confining themselves to certain rooms or houses, and hence not directly dependent upon any one host, is evidently true.

Remarkable, yes? Reminds me of WCW’s hat.

As if that were not vivid enough, Girault continues with this account of a colleague’s bed bug experience in an entomology lab:

Mr. William F. Fiske informed me that when stationed at Tryon, North Carolina, while working in the laboratory at night, bedbugs would crawl along the under sides of the edges of the table and stealthily approaching his bared arms, would attempt to feed.

Girault, A. A. 1905. The Bedbug, Clinocoris (=Cimex=Acanthia=Klinophilos) Lectularia Linnaeus. Psyche 12: 61-74. doi:10.1155/1905/10393

(What’s with Clinocoris… Acanthia? They couldn’t figure out what to call the bed bug at one time? Pity they didn’t ask us.)

I think Girault was having a bit of fun with the following, which he cited from an 1885 source, Lintner:

A correspondent wrote as follows: “ ‘Will you tell us something about the bed-bug, what its habits are, when it “spawns,” what it eats, how long it lives, and if it ever dies? I ask because I have moved into a house that I find was already occupied by several colonies of the pest. The room in which I have my library has the most. They are in my files of papers and periodicals. They seem to grow fatter every day, but for the life of me, I cannot tell what they live on. *******. Can it be that they live on the paste on the wall paper? As for remedies, ******. The latter (red pepper), I have sifted through my papers and books, and wherever I could get it; but instead of driving them off, they seem to fatten on it; ***************.****’ ” pp. 6-7.

And we may laugh at it too, for it is fantastic. What it eats!

Girault called bed bugs abominable. Actually, odious and abominable:

The trouble then is, that definitely stated facts are wanting concerning much of the life-history of this pest. This has doubtless been caused, partly on account of its being so common everywhere, and having an extensive literature, thus causing modern writers to believe it at first glance to be well studied, and partly because of its odious character and abominable nature. The last cause seems to have the most to do with it.

And:

It is the insect most directly affecting man, and the one, if any, which should be thoroughly studied, and yet, not until as late as 1896 (Marlatt, 1896 a) was its true life-history made known.

This is not scientific literature without personality. Girault could say of the body of a first instar that had just fed that it “became stained a very beautiful, deep, purplish red.” Nymphs are described as “sordid yellow.”

Like many, he fed bed bugs himself; except for 5th instars which caused “a distinct itching sensation,” he was not responsive to the bites. These are some of his notes on feeding bed bugs:

A single nymph or larva hatching during the morning of June 24th and isolated in a small glass vial, was fed at once. It was very active after hatching, and at first made attempts to escape, though in a few minutes readily took food. Just as soon as the least bit of blood entered the body it could be traced to its destination, and as more was sucked in, the body became stained a very beautiful, deep, purplish red. The abdomen, at first flt and round in outline, soon became distended, lengthened, and cylindric, and the nymph then measured 2.00 mm.a

On the afternoon of the next day (25th), the nymph was again fed, and the abdomen was much darker, not stained as previously. Again on the morning of July 6th, it was fed. It had not changed. On the morning of July 6th, it fed long and eagerly, until the abdomen became so large and distended that it was all out of proportion to the rest of the body; it was then stained purplish red, as after the first meal. The insect after this gluttonous meal did not lose its usual activity. The first molt then occurred about 7 P. M., 7th July. It had thus fed four (4) times during the first instar.

And his findings on feeding times for each instar:

The nymphs are very voracious, and at a single meal gorge themselves until unable to hold more. The time therefore given to each meal is limited by the capacity or size of the nymph at the time of any one meal, the capacity of course depending upon, or rather being more or less bounded by, the different instars. Hence, in each instar, the time taken for any single meal is more or less definite, shorter in the earlier, longer in the later instars, as the capacity is less in the earlier, greater in the later instars.

For its first meal after hatching, in instar I, it requires on the average, about three (3) minutes to glut itself, and if another meal is taken in this instar, a slightly longer period. In instar II, five (5) minutes; in instar III, six (6) minutes; in instar IV, eight (8) minutes; in instar V, ten (10) minutes, and when adult, from ten (10) to fifteen (15) minutes. These may be taken as averages, as the time for individuals varies somewhat.

He found that adults were unable to re-feed for at least 48 hours.

This is his table detailing the lifespan and the number of eggs deposited for two females, one fed and the other unfed:

oviposition and lifespan of fed and unfed female bed bugs - Girault 1905

I think of Girault sometimes. He pops into my head. I’m glad he was in the world. And wrote about bed bugs.

This is unprecedented stuff, so let’s take a very close look.

474 respondents, all with confirmed bed bug infestations, in Chicago, New York, Cincinnati, Louisville, Atlanta, LA and Miami. 66% living in apartments and 15% in single-family homes. All ages. 58% female, 42% male.

The breakdown for infestation level:

“Have you experienced any bites or skin reactions from the bed bugs in your dwelling?”

70% yes, 30% no.

Essentially the reverse of what was previously thought. Though there were also skeptics—see this note about last year’s article by Reinhardt and others.

The female/male differences were not statistically significant. And neither were ethnicity differences. The level of infestation was also not a factor.

Not so with age, however:

Significantly more people over the age of 65 reported no bites or skin reactions than those who were younger. Forty-two percent of the eldest individuals surveyed said they had no bites or reactions from bed bugs in their dwelling, whereas 26 percent of those aged 11 to 65 reportedly did not react.

This corresponds with an earlier survey where 76% of elderly tenants in one “severely infested” building did not react to bites (or reported not reacting). Possible reasons for this mentioned by the authors include reduced responsiveness to allergens in the elderly, medications that suppress the immune response (corticosteroids), and “diminished awareness due to other competing health issues.” For another discussion of a similar case, see the ASHES/Orkin white paper (PDF) from last year.

I think everyone is rightly worried about the elderly. Their infestations may go unreported, grow undetected, and then may be treated incorrectly.

Relationship to mosquito bites

The bed bug bite response reported in this survey corresponded with the level of mosquito bite response in the following way:

• “Barely visible” mosquito bite reactions = 53% reacted to bed bugs
• “Small (dime-size) welts” from mosquito bites = 77% reacted to bed bugs
• “Large (quarter-size)” / “severe (half-dollar size or larger)” mosquito bite reactions = 89% reacted to bed bugs

Characterizing the reactions of the 70%

• 72% had “itchy red welts”
• 50% had “redness or discoloration”
• 28% had “itching in the absence of welts”
• 21% had “a ‘pinprick’ or ‘stinging’ sensation”

Okay, let me pause here. On this last point the authors say: “which may or may not be symptomatic of bed bugs.”

Personally I have to say I can’t count the times people have reported this. Bed bugs!

There’s a lot more about the reported reactions.

The public health question, etc.

This is remarkable:

Other oft-mentioned symptoms from respondents living with bed bugs included nervousness, paranoia, anger, frustration, embarrassment, devastation and depression. Anxiety, stress, sleeplessness and depression are medically important symptoms that can lead to other conditions. Dismissing bed bugs as “not a public health pest” on the grounds that they are unproven disease vectors ignores the pain, suffering and emotional distress inflicted on their victims. When government agencies finally concede this point, additional resources may be allocated to combat the problem, as they were years ago.

I may have to put that on a post-it.

I hope they’re right.