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Family Philodromidae - Running Crab Spiders

Philodromus praelustris? - Philodromus Spider - Philodromus rufus Spider - Philodromus dispar - male Nursery Web Spider? Cricket thief - ventral - Thanatus vulgaris - male Tibellus maritimus  - Tibellus maritimus - female Spider ID Request - Philodromus Araneae
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Order Araneae (Spiders)
Infraorder Araneomorphae (True Spiders)
No Taxon (Entelegynes )
Family Philodromidae (Running Crab Spiders)
Explanation of Names
From Greek philodromos (φιλοδρομος)- "lover of the race/course"
Numbers
96 species in 5 genera in our region (1). The majority of the species are in the large genus Philodromus.
Identification
Philodromids tend to have the second pair of legs significantly longer than the first pair, which distinguishes them from the similar Thomisid crab spiders. In addition, thomisids have third and fourth legs that are shorter and more slender than the first two pairs of legs, while philodromid legs are subequal in length.
Internet References
~ PDF - Schick, R. X., 1965. The crab spiders of California (Araneae, Thomisidae). Range maps, keys, descriptions, & drawings of palps/epigynes.

Works Cited
1.Spiders of North America: An Identification Manual
D. Ubick, P. Paquin, P.E. Cushing and V. Roth (eds). 2005. American Arachnological Society.