Hangingflies belong to an unusual order of insects, the Mecoptera. Mecopterans (generally called scorpionflies) are not true flies and comprise of over ten extant families, the most notable and speciose being Panorpidae and Bittacidae. The morphology of Panorpids is reminiscent of that of a scorpion, but the stinger-like appendage on males is a genital capsule without a stinger or venom. Even though scorpionflies get most of the attention in this order, Bittacids (or hangingflies) also have fascinating predatory and courtship behaviors.
As adults, hangingflies have powerful hooked hind legs with claw-like extensions. They dangle from vegetation with their front four legs, ready to ambush and grasp prey that passes by. Once prey has been subdued, the hangingfly pierces the exoskeleton with its long beak and injects a tissue-dissolving enzyme that liquifies the interior of the prey. Robber flies (Diptera: Asilidae) have a similar method of prey consumption. This hangingfly (Harpobittacus cf. australis) I encountered was initially hanging by its two hooked legs with the other four splayed outwards (see photo below). I’m not sure if this is a normal position they adopt on vegetation, but it could be cryptic. I’ve always wanted to see their predatory behavior firsthand, so when I find another one I will spend more time observing it. Many species of hangingflies capture prey as a nuptial gift. Males emit pheromones from vesicles in the abdomen advertising availability to females, and a female will evaluate the quality of his gift. If the female accepts, she will begin eating the prey while the male initiates the mating process.
However, this was not the coolest fly-like insect I found in the Blue Mountains today… another post to come soon!
Beautiful and strange. The head is flat and long.
Beautiful and strange. The head is flat and long. The legs are closed together.