The Friday Beetle returns with an animal made famous by the late Tom Eisner:
If you can direct your attention away from the metallic colors for a moment, have a look at those massive foot pads. Eisner & Aneshansley (2000) noted the remarkable adhesive power of the pads and figured out how they work:
Abstract: The beetle Hemisphaerota cyanea (Chrysomelidae; Cassidinae) responds to disturbance by activating a tarsal adhesion mechanism by which it secures a hold on the substrate. Its tarsi are oversized and collectively bear some 60,000 adhesive bristles, each with two terminal pads. While walking, the beetle commits but a small fraction of the bristles to contact with the substrate. But when assaulted, it presses its tarsi flatly down, thereby touching ground with all or nearly all of the bristles. Once so adhered, it can withstand pulling forces of up to 0.8 g (?60 times its body mass) for 2 min, and of higher magnitudes, up to >3 g, for shorter periods. Adhesion is secured by a liquid, most probably an oil. By adhering, the beetle is able to thwart attacking ants, given that it is able to cling more persistently than the ant persists in its assault. One predator, the reduviid Arilus cristatus, is able to feed on the beetle, possibly because by injecting venom it prevents the beetle from maintaining its tarsal hold.
These colorful beetles are common on palmettos in the southeastern United States.
- Eisner T and Aneshansley DJ (2000) Defense by foot adhesion in a beetle (
Hemisphaerota cyanea). Proceedings of the National Academy of Sciences 97: 6568-6573.
- Hemisphaerota cyanea at the University of Florida
- Ted MacRae photographs a well-adhered beetle