When it creeps into your bed at night and crawls across your skin, the bedbug (inset) has to navigate a forest of body hair before plunging its proboscis into your flesh for a meal. One wrong step, and it could get smushed. Tickled by the question of how people detect such microscopic pests, researchers recruited 19 volunteers with various amounts of body hair and shaved one of each of their arms. They then asked the subjects to look away while they dropped bedbugs onto their arms. The volunteers hit a button as soon as they felt something crawling on them. Participants, especially men, with more hair follicles per square inch and whose body hairs were longer, tended to be several seconds quicker than less hirsute individuals to notice the bugs on their unshaven arms, the researchers report online today in Biology Letters. And everyone took a long time to notice the bedbugs on the shaved arm. That might explain why humans still have hair on their bodies, the researchers conclude, since we no longer need it for keeping warm.
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