Philodromidae and Thomisidae: Crab Spiders

Philodromidae and Thomisidae: Crab Spiders

These two families are called crab spiders. They have unusual body shapes compared to other spiders.

Philodromidae are the running crab spiders. They either ambush or run after prey. I often find them running along concrete walls on the bridges in Minneapolis. Pictured is probably Philodromus sp. Females are 4 to 8 mm, males are 4 to 6 mm, and legspans are 15 to 20 mm. Eggs occur in summer and Philodromus sp. overwinter as penultimate instars.

Thomisidae are the crab spiders. These spiders hunt by ambushing prey. Some species sit on flowers and change colors to camouflage themselves. They sit motionless and undetected on plants until an unfortunate insect is in reach. Pictured are probably Xysticus sp. I found several females with egg sacs and collected them. Apparently they emerge from the egg sacs as 2nd instars; however, a few of the egg sacs were damaged allowing me to photograph the tiny 1st instar babies. All were released. Xysticus females are 4 to 9 mm, males are 3 to 7 mm, and legspans are 12 to 18 mm. The yellow spider below, courtesy of Steve-o, is probably Misumena vatia.


Adult female	Adult female with egg sac	Mom and baby	1st instar on the tip of a paintbrush


2nd instar on a penny		More 2nd instar pics: so cute!


Xysticus sp. on scanner	Unidentified thomisid		Misumena sp.?

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