Very Hairy Feet
For humans and other mammals, hair plays three major roles: insulation, protection, and sensation of stimuli in the environment. On the other hand (or foot, as in the case of this beetle), insects have hair-like setae that likewise perform several roles. The function of the setae covering the undersides of this rove beetle’s forefeet is to increase its gripping power, allowing the beetle to firmly grasp and hold onto its prey – other small invertebrates.
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For humans and other mammals, hair plays three major roles: insulation, protection, and sensation of stimuli in the environment. On the other hand (or foot, as in the case of this beetle), insects have hair-like setae that likewise perform several roles. The function of the setae covering the undersides of this rove beetle’s forefeet is to increase its gripping power, allowing the beetle to firmly grasp and hold onto its prey – other small invertebrates.
What am I looking at?
This is an image of the foreleg tarsus, or foot, of a rove beetle (Platydracus maculosus). You are seeing two views of the foot – dorsal (1), from above, and ventral (2), from below. You can see the tarsal claws (3) at the tip of the last tarsomere; these give the beetle traction when it walks and help it grasp its food when it feeds. The fine hairs, or setae (4), serve the same purpose, helping the beetle adhere to smooth surfaces by creating a large contact area. The setae also augment this predatory beetle’s grip on its prey, which are often covered with a smooth exoskeleton.
The comb-like arrangement of bristles above the “ankle” (5) – that is, at the end of the tibia – is a grooming implement. When these beetles walk, the fine setae capture a lot of debris, which hinders their function. So the beetle uses the comb to scrape off accumulated debris by rubbing its forefeet together.
Click on the right arrow to see what the whole beetle looks like.
Biology in the background
Rove beetles are a large family of beetles, with 66,000 different species. As you can imagine, in a family that large there is a great deal of anatomical and behavioral diversity. Some species are scavengers or generalists, feeding on a variety of organic matter, dead and living. But some species prey on other insects. Because of this, they fulfill an important population control function within their habitats, preventing population booms that could potentially be harmful for the ecosystem.
Rove beetles vary in size quite a bit, ranging from 75 micrometers long, or roughly the width of a human hair, to over 35 millimeters long, or about twice the width of a human thumbnail.
Technique
These images were created using confocal microscopy.
Igor Siwanowicz, HHMI's Janelia Research Campus