In my last post I outlined the gruesome breeding habits of the spiny mason wasp, that provisions its nest with paralysed weevil grubs for its larvae to feed on at a later date. In the spirit of Jonathan swift's famous observation, that....
naturalists observe, a flea
Has smaller fleas that on him prey;
And these have smaller still to bite ’em;
And so proceed ad infinitum.
... here is the mason wasp's nemesis, the magnificently be-jewelled ruby-tail wasp Chrysis viridula. I watched this deadly little parasitoid's behaviour while I was photographing the mason wasp's nest, at the base of the cliffs at Hawthorn Hive on the Durham coast.
There are many species of ruby-tail wasp, also known as cuckoo wasps, each a parasite of a particular species of host wasp, and one thing that they have in common is relentless, restless activity, constantly using their downward-curving antennae to pick up a scent trail in the soil. Ruby-tail wasps have a thickly armoured, iridescent exoskeleton that's impervious to the stings of an angry victim. This species is less than a centimetre long and its colours are more exquisite than anything a jeweller could create.
Once it finds its host's nest hole it uses its antennae to explore the entrance, presumably testing for the specific scent that identifies its prey. Recent research suggests that ruby-tails can produce compounds in their exoskeleton that mimic the scent of their host and so avoid detection and counter-attack.
Next the ruby-tail crawls head-first into the nest hole, to make sure there's no one home, then ....
....... it climbs out and reverses in ....
... until only its metallic green head is visible in the entrance. Inside, it lays eggs that will hatch and produce larvae that will eat its host's young and their weevil grub food store. The hapless host , returning to seal its nest, will never know that the ruby-tail has visited and that its young are doomed.
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