We have a one-track mind here, no doubt, and so I’ve been looking for articles that discuss how bed bugs find their human hosts. Recently I read about the phases of host-seeking behaviors in blood-sucking insects—hungry searching, activation by stimuli and orientation, and finally attraction, “in which the decision of whether or not to contact the potential host is made”—Biology of blood-sucking insects, M.J. Lehane (1991), p. 26.

And I’ve found an interesting description of the orientation of bed bugs to certain stimuli, observed in a series of experiments investigating the bed bug’s attraction to human blood, sweat, sebum, etc. (Respectively: no, not really—complicated—and, yes.)

Aboul-Nasr A.E., Erakey M.A.S. 1968. Behaviour and sensory physiology of the bed-bug, Cimex lectularius L, to some environmental factors: chemoreception. Bulletin de la Societe Entomologique d’Egypte. 52:353-362:

When a cotton pad scented with sebum was demonstrated for bed bugs, these later might locate the source of stimulation through several orientating mechanisms. Analysis shows that this complete reaction may be separated into successive phases. The first phase involved a sudden rise of the insect body and the commencement of its antennal movements. The process of cleaning the antennae and proboscis with the fore legs may then follow.

Okay, let me pause here. And add superfluous emphasis!

The performance of such an excited condition represents an orthokinetic response. The second phase was shown in the crawling of the insect in a rather convoluted random track, i.e. klinokinesis. This would continue until the bug eventually comes in close proximity to the scented pad at which time it frequently heads directly for the source. In this reaction the insect seems to be orientated klinotactically (third phase). However, if the stimulus was only a short distance away at the begining, movements may be from the start and klinokinesis will not then be operated.

There is a very recent article, Olson et al. (doi:10.1016/j.jinsphys.2009.03.001), that may shed some light on this subject but it’s difficult reading and I’m still making my way through it.

I have not yet found any articles that discuss what induces bed bugs to begin probing, but there is a really great article (Ferreira et al.) about a different blood-sucking insect, Rhodnius prolixus, that suggests blood-sucking insects may find cues on their hosts skin, principally heat, to find blood vessels. Like R. prolixus, bed bugs are vessel feeders, excellent phlebotomists in that wonderful phrase… More on that another time maybe.

This Aboul-Nasr/Erakey article, by the way, is the earwax article. Did I tell you about this?

Reactions with cerumen (secretion of the external auditory meatus) agreed closely with those obtained for the oily secretion. This substance contains a great percentage of sebum together with a wax-like substance.

These pages may be of related interest:

1. Caught in a situation trap
2. Learning from the bed bug on the treadmill
3. Nocturnal forays, part 3: light, dark, and hunger
4. Investigating an acoustic monitor for bed bugs?
5. Nocturnal forays, part 2: on Demon traps