Zatypota albicoxa

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Zatypota is a genus of spider-hunting Ichneumon wasps in the sub-family Pimplinae. There are 40 known species of which 6 are on the NBN database for the UK, with just 40 records between them. Even allowing for the NBN lag, they are clearly few and far between.

Just 2 of those records (now 3) refer to Zatypota albicoxa, a parisitoid of the spider Parasteatoda tepidariorum (American House Spider).

This species has some interesting behaviours.

Two modes of oviposition have been observed.
In the first the wasp hung on the web, pulling the thread with its fore leg, until the spider lifted itself up, ambush-style, at which point the wasp pounces.
In the second, the wasp hung on the web at the mid-point next to the 'gumfoot thread' (a special, spring-loaded thread used by some spiders) and then flew at the spider from there as soon as it appeared.

Even more remarkable, the wasp appears to lay male or female-producing eggs by assessing the size of its victim, larger specimens hosting female-producing eggs. She does this not by expelling the eggs from the tip of the ovipositor. but from the tip of its abdomen.

Z. albicoxa is an ectoparasitoid, which lays its eggs on the outside of its host the emerging larvae eventually killing the host.