"Crypt-keeper" wasp tunnels through another wasp's head
January 25, 2017
Think you're having a bad day? Well, feel for the gall wasp. This unfortunate parasite digs its way into an oak tree to reproduce only to be parasitized by another parasite.
The gall wasp's (Bassetia pallida)cosy little home becomes a grisly prison whenEuderus Set pops by - scientists named it after Set - the Egyptian god of evil and chaos, who chopped up his brother Osiris, for good reason.
E.Set, the head burrowing, crypt-keeper wasp.Credit: Andrew Forbes/University of Iowa
The gall wasp's larvae forms compartments around it, known as a crypt, protecting it from harm until the larvae is ready to burrow its way out into the big wide world during the spring. But when E.Set rocks up and drops an egg into the crypt, things take a turn for the worse.
E.Set's egg starts to influence the gall wasp larvae, making it dig its usual escape hole too small for it to fit though. When the gall wasp does the completely reasonable thing and tries to escape it gets stuck, with only its head protruding out.
Dinner time for E.Set beckons. It chows down on the gall wasp's innards and uses its body as an edible ladder until it emerges through its head - by now, the gall wasp is, mercifully, well dead.
The scientists who discovered the crypt-keeper sought to find out how important the gall wasp is to the dastardly parasite. It turns out its incredibly important. In a sinister experiment, that matches E.Set's dastardly ways, the scientists taped thin strips of bark over dead gall wasp heads, then they waited.They found E.Set was three times more likely to die in the crypt if it had the added challenge of gnawing through the bark, after breaking through its host's head.
But they don't know much else about what goes on inside the crypt. They don't know for instance how E.Set makes its gall wasp victim burrow a smaller hole than usual.
"It could be that the parasitoid cues hosts to excavate early, but makes it do less well than usual," Kelly Weinersmith, an evolutionary biologist at Rice University in the States. "They only go part way and then they get stuck."
They plan to use a CAT scan on branches where wall wasps are being entombed to really get a grip on what's going on. For many of us of the more squeamish disposition, that may not necessarily be a good thing.
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