Beetle with a Click

Explanation: This sleek insect has quite a hidden trick.

This is a click beetle ... so named because, when it is disturbed, it flexes its back and flips into the air, making a sharp clicking sound, startling the potential predator enough so that it gets away.

What an interesting adaptation! The only other analogue I can think of in the insect world is how some grasshoppers will make wing-clicking sounds as they alight into the air when disturbed. In general, this is called "flash behavior" in prey species that use sound, color, or other behavior to startle a potential predator. (I've been startled more than once by this, myself, walking through fields.)

So what makes the click sound in a click beetle?

They snap a small spine that protrudes from the underside of the thorax (from the prosternum) into a groove under the mesothorax (the mesosternum).

Quite an interesting and very specialized adaptation that serves no function other than ... click.

In forests, some click beetles prey on other insects including forest pests; some dig under tree bark and decaying wood; and many live in the soil and are mostly unstudied.

There is a similar-appearing family of "false click beetles" (family Eucnemidae) in which their clicking and flipping behavior is poorly developed. In true click beetles, the antennae extend from near the eyes, as shown in the photos here, rather than from between the eyes as in the false click beetles. Also, true click beetles often have antennae that are comb- or sawtooth-like, also shown in these photos.

How interesting is this tiny insect!

Information:
     Evans, A. V. 2008. Field guide to insects and spiders of North America. Sterling Publishing, New York. 497 pp.
     Furniss, R. L., and V. M. Carolin. 1980. Western forest insects. Miscellaneous Publications 1339. USDA Forest Service, Washington, D.C. 654 pp.
     Haggard, P., and J. Haggard. 2006. Insects of the Pacific Northwest. Timber Press, Portland, Oregon. 295 pp.

EPOW - Ecology Picture of the Week