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Common Crab Spider Xysticus cristatus / Xysticus kochi

The Common Crab Spider is common indeed, but does present us with a problem. There are two species of Common Crab Spiders. And both are common! They can only be told apart by studying the genitals under a microscope. All other methods, however accurate they may appear, fail. So we do not know whether the little bugger in the pictures is Xysticus cristatus or Xysticus kochi.

The Common Crab Spider is often seen in gardens and may even climb walls, fences etc. It runs towards an unexpecting prey and jumps on it. Its poison is powerful enough to kill even very big insects, much bigger than the spider itself is. But the Common Crab Spider not only hunts for big prey, it also eats very small insects, such as thrips. Actually Xysticus kochi is used in greenhouses to control infests of thrips in the breeding of peppers.

For many male spiders mating is dangerous. Most females will not hesitate to eat her partner. The male Common Crab Spider found some kind of solution. When he approaches a female for mating, he will jump on one of her legs. Even though she struggles to get free, he holds on. When she is done struggling he will cover her up with threads, untill she can't move anymore. Only then will he crawl beneath her to mate. Females measure op to 8 millimeters, males are just 4 to 5 millimeters in length.