Evolution has repeatedly turned hawkmoth genitals into defensive tools
The genital structures of male hawkmoths are lifesavers. By rubbing specialized scales on their genitals against parts of their abdomen, the nocturnal insects emit ultrasonic sounds that can potentially scramble the acoustic signals that bats use to hunt.
Hawkmoth genital structures serve as lifesaving defense mechanisms against predators, such as bats. By rubbing specialized scales on their genitals against various parts of their abdomen, these nocturnal insects emit ultrasonic sounds that can interfere with the acoustic signals bats use to hunt. This arms race between hawkmoths and bats has been ongoing for millions of years.
However, questions persist about how frequently these defenses have evolved independently and why different hawkmoth species have developed distinct methods for producing ultrasound. To investigate this, researchers studied 124 hawkmoth species, examining their genital structures and sound-producing mechanisms. They discovered that the anti-bat sound responses have evolved independently up to seven times over the past 30 million years.
Three distinct strategies emerged for producing ultrasound, each involving rubbing specialized genital scales against different structures on the abdomen: other scales, tiny spines, or small bumps called nodules. The resulting ultrasonic sounds varied in pitch, burst length, and duration. Notably, hawkmoths with hearing organs generally produced sounds with greater potential to disrupt bat sonar, while some species without hearing organs also emitted ultrasound when touched. This could serve to startle predators or mimic other moths instead of jamming bat hunting signals.
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