Gasteruption (Hymenoptera: Evanioidea: Gasteruptiidae)
Gasteruption (ghost wasps) is the largest genus of the small wasp family Gasteruptiidae. Worldwide there are only about 500 species in the family, most of them in tropical and subtropical areas. Gasteruption individuals are somewhat bizarre in appearance and behaviour, consequently fascinating. Unmistakeable, particularly in flight, the adults have a long “neck” (pronotum) tapering towards the head to which the rest of the body is attached, looking somewhat like an evolutionary afterthought. The abdomen is attached to the thorax high up on the propodeum, making them easy to identify. When flying, the somewhat swollen hind legs hang down towards the ground while the abdomen projects posteriorly from the thorax at a more or less 90ᵒ angle. Others have observed that Gasteruption in flight resembles a helicopter, an opinion I share. The wings, fluttering slightly forward from the rest of the body enable the wasp to search effectively for prey nests. (https://twitter.com/ParslowBen/status/1454750407851266050). This is a 10 second or so video of Gasteruption in action – do not miss it.
Gasteruption are predator-inquilines of aculeate Hymenoptera, particularly bees, killing and eating the host bee larvae and other provisions like pollen and nectar within the host nest they hijack and develop in. The nests they seek are usually vertically oriented either in soil banks or wood. They are the primary enemies of Hylaeus bees (Colletidae). Another fascinating group, Hylaeus females are known for their unique pollen processing behaviour whereby the female bee swallows pollen and nectar and after entering her nest regurgitates the food for her larvae to eat. Unfortunately, sometimes they do not survive the period of larval development – and so it goes.
Credits: Dr Robert Copeland