Philodromus – Running Crab Spider

Philodromus - Running Crab Spider

Philodromus, commonly called running crab spider, is a genus of crab spiders. Various species can be found throughout the entire Northern Hemisphere and the United States.

Running crab spider description

The Running Crab spider is usually a brown or a gray color with very little markings if any. The second pair of legs on the Running Crab Spider is always longer than the rest of the legs. In the picture above, however, it seems this one lost the second leg on its left side. It is a common occurrence in the spider world as they will often let a leg be taken to escape a battle alive, and they will usually grow a new one back.

Picture of Philodromus - Running Crab Spider
The running crab spider. Photography by: K. J. Ester – Madison Heights, Mi.


The body will reach up to about 3/4 of an inch (19 mm) and with the legs included may be around 1 ½ inches (38 mm).


The Running Crab Spider is a hunter spider. It does not use a web to catch prey. The only time they spin webs is to make egg sacs and to lay drag-lines in case they fall.

Running Crab Spider
A Philodromus margaritatus running crab spider


The bite of the Running Crab Spider usually results in some local pain and swelling. On a rare occasion, it can cause prolonged pain, inflammation and headache. Sometimes, a bite of the running crab spider can even lead to vomiting and irregular pulse rate. However, this is rare enough that they fall under the Low Risk category.

Philodromus scientific classification

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Chelicerata
  • Class: Arachnida
  • Order: Araneae
  • Infraorder: Araneomorphae
  • Family: Philodromidae
  • Genus: Philodromus

Distribution of the running crab spider in the USA

Philodromus running crab spider range

Various species of the running crab spider can be found throughout the Holarctic region and in every state of the US: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming

Philodromus – Running Crab Spider

20 thoughts on “Philodromus – Running Crab Spider

  1. There are several of these spiders hanging around the eaves of my house in northern NH. Now that the temperature is cooling significantly, they are still there, only now with what appears to be tightly woven “egg sacks“(?). The spiders appear to be approximately 1 1/4 – 1 1/2” in total diameter.

  2. My wife was bitten a few days ago by an unknown insect in her pants – we couldn’t find it.
    Then this morning this appears on our wall.

  3. What type of spider is this? I found two in the house within a week. Never seen them around the house before.

  4. Please identify Spider found in a uniform web on the ceiling of my bathroom in Bradenton Florida.

  5. I think this may be a Running Crab Spider. It was on my driveway and was not bothered by me taking a photo of it. I touched and it barely moved. An hour later it was gone. It appeared to be about the size of a half dollar, 1inch to 1 1/2 inch. Dark brown and about the same all over with no distinct coloring, maybe some white marks on main body. Salem, Missouri

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