Reinhardt, K., Isaac, D., & Naylor, R. (2010) Estimating the feeding rate of the bedbug Cimex lectularius in an infested room: an inexpensive method and a case study. Medical and Veterinary Entomology 24, 46-54. doi:10.1111/j.1365-2915.2009.00847.x
The authors developed a method, with potential forensic applicability, to determine the time from the last bloodmeal based on measurements of the abdomen — actually a ratio of the abdomen size and width of the thorax, its average decrease over several hours with the process of digestion, at different temperatures:
The overall procedure for our method was as follows. Firstly, we quantified the decline in abdomen size of fully fed animals at different temperatures. Secondly, we tested whether the propensity to feed is temperature-dependent and, thirdly, we measured the shrinkage of the bugs’ bodies in the most commonly used preservation media, 60% and 96% ethanol. In a case study, we then applied this method to measure the digestion status of bedbugs in a naturally infested room and to calculate an average feeding rate for bedbugs in that room.
As for the room in question, I am grateful for the reserve of these researchers who describe the room simply like this:
Samples of bedbugs were collected from 21 harbourages in a heavily infested dwelling in London (Figs 1 and 2) in June 2007. The temperature in the infested room was maintained by a thermostat at a constant 26° C throughout night and day. The only tenant of this apartment was an elderly man who kept most of his newspapers, books and other belongings in stacked piles throughout his home (Fig. 2). Harbourages were mainly found in the stacks of newspapers, which were at most separated by a few centimetres (Figs 1 and 2).
Yes, there is a graphic photograph in the article, but what you really want to see is this drawing:
schematic drawing of an infested room - Reinhardt, Isaac, Naylor 2010
From this room, from all those harborages in newspaper stacks, they collected “a small proportion” of the total bed bug population. 3,750 bed bugs. (So this is how lab colonies are built…) Some were kept alive and some were preserved in ethanol, hence the need to figure out how much bed bugs shrink in ethanol.
The average time from the last bloodmeal for female bed bugs in this room was 2.5 days (at a temperature of 26dC/78.8dF), which is at the low end of a 2-4 day feeding interval estimate for this temperature. In lab conditions, the authors say that feeding rate increases as the temperature increases (1-3 days at 32dC/89.6dF vs 5-9 days at 18dC/64.4dF).
(Mellanby previously estimated that adults fed every 5-6 days at temperatures between 20-27dC/68-80.6dF. And by the way he had to paint individual bed bugs and recapture them on their feeding excursions… his “natural” infestation was in rat cages.)
One wonders if it’s not just temperature and if feeding intervals would be different in a lower-density infestation.
You might remember, Pfiester et al. observed that the percentage of female bed bugs grouped together rises with population density, especially in female-biased aggregations. Well, the sex-ratio in all those paper stacks in this study was definitely female-biased, 65.8% of adults collected.
The graphs in the drawing above show the mean number of days since the last bloodmeal for each harborage location they represent (these are female bed bugs in harborages that contained more than 10 adult females). Notice the difference between harborages immediately next to each other on the bed? The authors don’t know what accounts for this but, as ever, it may have to do with mating:
These differences between harbourages cannot be attributed to temperature differences because they were found in the same confined room. They are also unlikely to be caused by the switch of sleeping sites (between sofa and bed) of the inhabitant of the apartment because harbourages that were next to each other differed in feeding stage distribution (Fig. 1, Table 3). There is a possibility, however, that the tendency towards synchronous feeding may be related to the mating biology of bedbugs. Mating and feeding are closely linked in bedbugs because fed females cannot avoid mating (Reinhardt et al., 2009b). Males control the mating rate of females and frequent mating reduces female lifespan and egg production (Stutt & Siva-Jothy, 2001). As females cannot reduce feeding without ceasing reproduction, Reinhardt et al. (2009b) speculated that females might lower male attention by engaging in synchronized feeding.
Fascinating.
But all I can think about is that poor man, futilely alternating between the bed and the sofa, trying to find relief.
These pages may be of related interest:
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