If you ever find yourself in South Africa during southern spring, and stay up long into the night, until midnight at least, you may be rewarded with one of the most incredible acoustic displays that the insect world has to offer. For this is the time when the bladder grasshoppers, known in Africa as the flying gooseberries, begin to sing.
These insects are rather strange. They are grasshoppers, placed in their own family Pneumoridae, but it would be difficult to tell by looking at one. To begin, they are huge – some species are the size of a small mouse. Their legs are thin and spindly, and they cannot really jump. But what they lack in athletic abilities is amply compensated by their ability to make noise.
Flying gooseberries produce sound in a way similar to other grasshoppers, by rubbing their hind legs against a row of pegs on their abdomen (to be exact, most grasshoppers rub their legs against a modified vein on their wings, but the principle is the same.) This in itself wouldn’t be unusual, if not for their ability to amplify the sound. The male’s abdomen – because it is he who produces most of the sounds – has evolved to become an enormous, balloon-like structure, filled with air and acting as a powerful resonator. This allows him to broadcast his song at distances that have no parallels among insects – a single male can be heard from over a mile away. (Click here to hear a flying gooseberry’s song.) The males can also fly, and are sometimes attracted to camp fires at night, which is the reason for their vernacular name (and if they get too close to the flames they promptly explode.)
The female is nowhere near as extrovert, and she only responds to the male’s call with short, quiet clicks, which the male can hear from over 50 m despite the racket he himself is producing. By being much quieter she also avoids the risk of being detected by predators and parasitoids, some of which use the insect’s calls to locate their prey. But in every population some males of flying gooseberries take advantage of the fact that the singing rival gathers all the attention. Rather than singing themselves they stay quiet, and sneakily intercept the females attracted by the caller. They even assume the appearance of females by not developing wings or the enormous abdomen. This prevents them from being chased away by the singing male, who confuses them with the real deal. This to me proves it once again that insects were the first to invent pretty much every behavior imaginable, including the transvestites.