Roach love songs

It’s hard to feel romantic around cockroaches, but some male roaches whistle soft music to entice their sweethearts. The whistled sounds are surprisingly complicated and even almost birdlike.

While courting a female in dim red light, a male cockroach forces air through holes in his abdomen to make soft, enticing whistles.

Jérôme Sueur, University of Paris XI-Orsay

The chirps, trills, and squeaks of many insects, including most other kinds of roaches, come from the rubbing of legs or other body parts against each other.

Mammals and birds, on the other hand, use their breath to make noises. Hissing cockroaches are among the few insects that communicate this way, too. You may have seen giant hissing cockroaches in pet stores or at insect zoos.

When threatened by a predator, hissing cockroaches make loud hisses. Researchers have found that some male roaches also make soft, whispery sounds to get the attention of females.

In the new study, researchers from France focused on the songs of a roach species called Elliptorhina chopardi, which are smaller than the giant hissing cockroaches found in pet stores. During the experiment, a male and a female cockroach shared a piece of wood under a dim red light. For 2 hours, the scientists watched and recorded sounds as the male tried to convince the female to mate with him.

The recordings included sounds in the air and vibrations traveling through the wood under the roaches’ feet. No one has yet studied how E. chopardi hears, but some roaches have “ears” on their legs below the knees. So, it’s possible that the creatures can “feel” sounds through the ground.

The scientists divided the recorded sounds into three categories: hisses, noisy whistles with static-like fuzz, and complex, pure whistles.

The pure whistles sometimes sound like two, intertwined voices. In this case, a roach squirts air through the holes in its abdomen so that it plays two songs at once. That’s like having a person with two mouths, each one whistling a different tune.

The results showed that males didn’t mate unless they made their sweet whistling noises. This finding backs up older research, which found that giant hissing cockroaches, which don’t sing, have to make certain sounds to partner up.—E. Sohn

Going Deeper:

Milius, Susan. 2006. Hey, roach babe: Male cockroaches give fancy courting whistles. Science News 170(Sept. 9):165-166. Available at http://www.sciencenews.org/articles/20060909/fob6.asp .

View a colony of giant Madagascar hissing cockroaches at cricket.biol.sc.edu/usc-roach-cam.html (University of South Carolina).

Science project idea: Learn about raising hissing cockroaches for study at www.uky.edu/Ag/Entomology/entfacts/misc/ef014.htm (University of Kentucky).