A Running Crab Spider — Philodromus histrio

Running Crab Spider -- Philodromus histrio (Latreille, 1819) on Euphorbia bloom.

Running Crab Spider — Philodromus histrio (Latreille, 1819) on Euphorbia bloom.

Philodromus histrio is found worldwide across the northern hemisphere, this one was found in our front garden in Edmonton. In Sweden the name is Praktsnabblöpare, translating to “Magnificent Fast Runner”. The only site that carried some of the life-history of this spider is the Spider and Harvestman Recording Scheme website for Britain, which states that the following under the sub-heading Habitat and Ecology:

P. histrio usually occurs on heather in heathland, where the female encloses her egg-sac in silk and bits of dried heather. The spider, whose red-brown colour and whitish markings provide excellent camouflage against the background, may be found guarding her egg-sac. There is a most interesting variety found on saltmarsh in Essex (where the heathland form has not been recorded) in which the spider has the reddish-brown replaced by the bluish-green colour of Sea Purslane Atriplex portulacoides. Adults of both sexes occur mainly in May and June.

Dorsal view, showing the distinctive pattern on the abdomen

Dorsal view, showing the distinctive pattern on the abdomen.

Misumena vatia on Aster

Misumena vatia with first two pairs of legs equal length.

Philodromidae are not closely related to Thomisidae, although they both share similar hunting strategies, spinning webs only for drag-lines and to protect eggs. The simplest way to differentiate the Philodromidae from the true crab spiders in the family Thomisidae (such as Misumena vatia, the Goldenrod Crab Spider) is by taking a close look at the legs: as you can see clearly above, the second pair of legs in Philodromids are longer than the front pair.

 

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