Friday Beetle Blogging: Palmetto Tortoise Beetles

The Friday Beetle returns with an animal made famous by the late Tom Eisner:

Hemisphaerota cyanea, photographed in Gainesville, Florida

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.

2 thoughts on “Friday Beetle Blogging: Palmetto Tortoise Beetles”

  1. These and the flatid Ormenaria rufifascia are great reliable insects on palmetto. Nice shots! They are difficult to make nice images of with their small heads.

  2. Andres Gonzalez

    I was a graduate student of Tom Eisner during the 90s, I remember well this nice story about palm beetle foot adhesion. There was a funny video, I think from the BBC. Thank you!

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