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Family Philodromidae - Running Crab Spiders

Spider ID? - Tibellus Unknown Philodromidae? - female a spider  - male - female spider - Tibellus Spider Running Crab Spider - Philodromus Spider-Cambridge, MA - Philodromus Thanatus in Aurora  - Thanatus formicinus - female
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Order Araneae (Spiders)
Infraorder Araneomorphae (True Spiders)
No Taxon (Entelegynae)
Family Philodromidae (Running Crab Spiders)
Explanation of Names
From Greek philodromos (φιλοδρομος)- "lover of the race/course"
Numbers
Spiders of North America 2nd Edition states that there are 92 species in 6 genera in our region (1). A 2016 paper added another genus (Rhysodromus)(2).
The majority of the species are in the large genus Philodromus.
Identification
Not diagnostic, but some helpful features:(3)
Second pair of legs longer than first
All legs similar in size (Thomisids have back pair smaller than front pair)
Often with a stripe on the back of the head
2 Claws
8 eyes
Flat bodied
Legs laterigrade


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.
Range
Widespread
Habitat
Often found on plants (stems & leaves).
Food
These spiders are active predators.
Print References
Schick, R. X. (1965). The crab spiders of California (Araneida, Thomisidae). Bulletin of the AMNH; v. 129, article 1. (Full Text Here)

Dondale, C. D., & Redner, J. H. (1978). The Crab Spiders of Canada and Alaska (Araneae: Philodromidae and Thomisidae)(The Insects and Arachnids of Canada, Part 5). Agriculture Canada Publication, 1663. (Full Text Here) - With free account
Works Cited
1.Spiders of North America: An Identification Manual, Second Edition
Darrell Ubick (Editor), Pierre Paquin (Editor), Paula Cushing (Editor), Nadine Dupérré (Illustrator). 2017. American Arachnological Society.
2.The spider genus Rhysodromus Schick, 1965 in the Crimea (Aranei: Philodromidae)
Kastrygina and Kovblyuk. 2016. Arthropoda Selecta.
3.Spiders of North America: An Identification Manual
D. Ubick, P. Paquin, P.E. Cushing and V. Roth (eds). 2005. American Arachnological Society.