Crabby

European Green Crab Spider (Diaea dorsata)

One thing we quickly learned when trying to identify things in the garden – some spiders are hard! Many can only be identified by dissecting their genitalia, or other equally lethal methods. We're not at the point where we want to do anything of the sort, so many of the species we find go unidentified. Fortunately, there are some spiders that don't require such extreme measures, and one of them made an unexpected appearance this week. I say unexpected because although the European Green Crab Spider (Diaea dorsata) is widespread across the southern half of England, it's still pretty uncommon across this corner of Norfolk. When I entered the record into iRecord (the national database), I got a message saying it was "outside the known range of this species". 

The European Green Crab Spider is so named because its long legs and scuttling movements bear a strong resemblance to a real crab. It's quite small though; the female's body is only about 6 mm (1/4-inch) long, and the male's is even smaller, though the long legs of both sexes help to make them seem larger. In a cool adaptation, it can change its colour to blend in with its surroundings, a process that takes several days. Based on its size, the individual we saw appeared to be a female. With any luck we'll find a male. Or preferably two! Males compete by facing off with their front legs outstretched and dancing around each other – reportedly sometimes for hours. It would be fun to see such a combat. Our handy reference guide, "Britain's Spiders", says the species is strongly affiliated with woodland and prefers evergreen foliage, so I'm not quite sure how (or why) it ended up on our Norway Maple trunk, but we're glad it did!