Hawkmoths squeak their genitals at threatening bats

An approaching predator inspires ultrasonic rasping in insect prey

SOUNDING A DEFENSE  Reproductive structures at the rear tip of this hawkmoth (Theretra nessus) from Malaysia can create noises too high for human hearing but audible to attacking bats.

J. Barber and A. Kawahara

View the video

Sonar pings from a hungry bat closing in can inspire hawkmoths to get their genitals trilling.

The ultrasonic “eeeee” of scraping moth sex organs may serve as a last-second acoustic defense, says behavioral ecologist Jesse Barber of Boise State University in Idaho. In theory, the right squeak could jam bats’ targeting sonar, remind them of a noisy moth that tasted terrible or just startle them enough for the hawkmoth to escape.

Males of at least three hawkmoth species in Malaysia squeak in response to recorded echolocation sounds of the final swoop in a bat attack, Barber and Akito Kawahara of the University of Florida in Gainesville report July 3 in Biology Letters.  

Female hawkmoths are hard to catch, but the few Barber and Kawahara have tested squeak too. Although they’re the same species as the males, they use their genitals in a different way to make ultrasound. Squeak power may have arisen during courtship and later proved useful during attacks.

Until now, researchers knew of only two insect groups that talk back to bats:  some tiger moths and tiger beetles. Neither is closely related to hawkmoths, so Barber speculates that anti-bat noises might be widespread among insects.

Slowed-down video shows first the male and then the female hawkmoth creating ultrasonic trills at the tips of their abdomens. Males use a pair of claspers that grasp females in mating. To sound off, these quickly slide in and out of the abdomen, rasping specialized scales against the sides. Females rub the left and right sides of their abdominal structures together.

Video credit: Jesse Barber & Akito Kawahara

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

More Stories from Science News on Animals