Tags
British parasitic wasps, ectoparasitic idiobiont, metallic green wasp, parasitic wasp, Torymidae, Torymus species, Torymus species on Common fleabane
This stunning little creature was another find from my favourite fleabane field last Sunday. I’m fairly sure she’s one of the Torymidae, a large and diverse family of parasitic wasps that are characterised by the metallic sheen of their bodies, the long ovipositors of the females, and the large size of their hind coxae (the first segment of their legs). They are also very small, ranging between 1 and 7mm in length.
As I watched, this particular wasp probed the Common fleabane seed head, searching with her ovipositor for gall-fly larvae to parasitise. On Monday, at a different location, I found another female, pictured in the two images below, who was also probing fleabane flowers.
From what I’ve been reading, the many Torymus species use different forms of parasitism but the majority are ‘ectoparasitic idiobionts of various concealed hosts’, meaning they first paralyse or kill their hosts to prevent them escaping, then lay their eggs on the outside of the host’s body, so that, once the wasp’s eggs hatch, they consume their host from the outside, rather than living within it. From a human perspective, it’s a very unpleasant practice but parasitism is quite common in the insect world.
In this particular case, I assume the hosts are the larvae of gall-causing fruitfly species like Myopites inulaedyssentericae that I blogged about last week, and I had hoped that might narrow down the possibilities for the Torymus species I’ve found, but I haven’t yet managed to put an exact name to them.
