There are several wasp species across the world that have a
life cycle that involves them becoming parasites of other creatures. One of
these is a Costa Rican wasp (Hymenoepimecis argyraphaga) that targets a particularly
formidable spider (Plesiometa argyra).
The spider is large and fearsome, and therefore avoided by just
about every other insect apart from females of the wasp. It hovers above the spider
then lands directly on its back, where it lays a single egg before making its
escape.
The spider is not affected by this visit at first, but in time
the egg absorbs nutrients from the host and the larva that hatches from it injects
the spider with a chemical that makes it act in ways that it would not
otherwise have done.
The night before the larva is ready to pupate, the spider
destroys its web, which is not unusual given that many spiders do so as part of
their regular behaviour. However, when a new web is spun, it is very different from
what went before because its purpose is entirely to benefit the wasp and not
the spider.
This web is hardly a web at all, because it consists of strands
of strong silk that provide an anchor to nearby plants. When finished, the
spider hangs beneath this framework and never moves again.
The wasp larva then eats the spider, and by dawn it is ready
to weave its own cocoon which hangs inside the rough web made by the spider. It
will then take its time in transforming into an adult wasp, protected inside its
cocoon which in turn is safe from ants and the effects of heavy rain thanks to
the strong threads that the wasp forced the spider to weave.
Nature has managed to produce some amazingly unpleasant
creatures!
© John Welford
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