Three groups of insects, crickets, katydids and cicadas may be called insect musicians. The first two, crickets and katydids create sound by stridulation, i.e. rubbing specially modified body parts against each another. Cicadas on the other hand have a unique noise making organ, a tymbal which is located on the front side of the hollow body of the male and acts as a sound box. By contracting muscles acting against the tymbals, the cicada produces very loud, penetrating calls, and each species has its own song which is recognised by all individuals of the same species.
In most cases it is the males that are calling in order to attract mates. Female calling is unusual other than in some cicadas where a female responds to a nearby male by flicking her wings to make a high-pitched ‘tick’.
It is, however, the recent recordings we made of two other insect species, a dung beetle and a spider-hunting wasp that prompted us to delve into the literature and write this blog. Both of these sounds are made while the insect is flying around, in the case of the dung beetle a loud buzzing sound, while the wasp makes a loud clacking sound – but how do they make this sound and what is the purpose?
Telecoprid Dung Beetle. Rolls ball away from dung.
Paracoprid Dung Beetle. Digs tunnel below dung to bury it.
Fascinating research has been conducted on a dung beetle genus (Aphodius) common in north temperate ecosystems. This genus is mainly classified as endocoprids which lay their eggs within the dung pat itself. This research has shown that these beetles produce vibrations within the dung by means of a file on the ventral part of the wing that rubs against a scraper on the abdominal region of the beetle. It is hypothesized that females use the information within the song in the context of mate choice. What about the many species that occur here in southern Africa?
Despite extensive searching through the literature, we have been unable to find out anything about the buzzing flight sound made by the dung beetles around our home. Do all species make this sound in flight, do they use the file and scraper mentioned above to make this sound, and once again, what is the purpose?
Dung Beetle in flight
The large black Pompilid, or Spider Hunting Wasp that we recorded was collecting nectar from a huge Euphorbia cooperi in front of our house and would fly from one part of the plant to another making this peculiar rattling sound – but it is not known why they make this noise. It has been suggested that they make the noise with the wings – but exactly how is it done?