slow running crab spider

(Philodromus placidus)

Conservation Status
slow running crab spider
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

     
  Minnesota

not listed

     
           
           
           
 
Description
 
 

Slow running crab spider is a small spider. It is difficult to see due to its small size and mottled brown coloration that blends into the background. It occurs in the United States from Maine to Virginia west to Oregon and Colorado, and in Alaska and Canada. It is widespread but not common. It is found mostly in the foliage of conifers but also on other trees.

The adult female is to 316 (3.5 to 5.0 mm) in length, not including the legs. The male is only slightly smaller, (3.0 to 3.5 mm) in length. The body is soft and flattened.

The covering (carapace) of the front part of the body (cephalothorax) is somewhat flattened, as wide as long or wider than long, and smoothly rounded on the sides. It is creamy white with some brown spots in the middle and brown mottling on the sides. On the male the upper side is coated with shiny scales. There are eight eyes arranged in two rows of four. None of the eyes are on raised projections, (tubercles), and all of the eyes are small. The four eyes in the back row are all the same size. The posterior median eyes (PMEs) are closer to the posterior lateral eyes (PLEs) than they are to each other.

The abdomen is somewhat flattened, longer than wide, and a little pointed at the rear. It is creamy white above and brown on the sides. The upper side is sprinkled with small brown spots. There is a dark brown dash on each side about two-thirds of the way back that extends into the creamy white area. On the male the upper side is coated with shiny scales.

The male is darker than the female, most are much darker, with less contrast between the dark and light areas.

The legs are long and slender. They are longer and thinner on the male than on the female. They first, third, and fourth pairs of legs are nearly the same length and thickness, the second pair is only slightly longer. The front two pairs project outward rather than forward (laterigrade), allowing the spider to move quickly sideways, like a crab. This is the feature that gives the superfamily its common name. The legs are mostly pale but have a dark area at the end of each segment and a dark area in the middle of the third segment (femur). The first four segments of each leg are armed with long, stiff, spine-like hairs. The last leg segment (tarsus) has a two claws, a dense, brush-like tuft of microscopic hairs below (scopula), and a dense, brush-like tuft of microscopic hairs at the end (claw tuft). The claws, scopulae, and claw tufts are not visible to the naked eye.

 
     
 

Size

 
 

Female Body Length: to 316 (3.5 to 5.0 mm)

Male Body Length: (3.0 to 3.5 mm)

 
     
 

Web

 
 

Running crab spiders do not build snares, retreats, or nests.

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Foliage of mostly coniferous trees but also other trees

 
     
 
Biology
 
 

Season

 
 

May through August

 
     
 

Behavior

 
 

The adult is able to move very fast. Its movements are rapid and erratic. While it may wait in ambush, it often hunts by running after prey. This is the feature that gives the family its common name.

 
     
 

Life Cycle

 
 

 

 
     
 

Food

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 29, 30, 82.

 
  12/23/2021      
         
 

Occurrence

 
 

Widely scattered but not common

 
         
 
Taxonomy
 
  Class Arachnida (arachnids)  
 

Order

Araneae (spiders)  
 

Suborder

Araneomorphae (typical spiders)  
  Infraorder Entelegynae (entelegyne spiders)  
 

Superfamily

Thomisoidea (crab and running crab spiders)  
 

Family

Philodromidae (running crab spiders)  
 

Genus

Philodromus  
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

slow running crab spider

 

 

 

 

 

 

 

Glossary

Carapace

The hard, upper (dorsal), shell-like covering (exoskeleton) of the body or at least the thorax of many arthropods and of turtles and tortoises. On crustaceans, it covers the cephalothorax. On spiders, the top of the cephalothorax made from a series of fused sclerites.

 

Cephalothorax

The front part of the body of various arthropods, composed of the head region and the thoracic area fused together. Eyes, legs, and antennae are attached to this part.

 

Femur

On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.

 

Tarsus

On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.

 

 

 

 

 

 

 

 

 

 

 
 
Visitor Photos
 
           
 

Share your photo of this arachnid.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Attach one or more photos and, if you like, a caption.
 
 

Alfredo Colon

 
    slow running crab spider   slow running crab spider  
           
 
MinnesotaSeasons.com Photos
 
 

 

 
           

 

Camera

     
 
Slideshows
 
 
     
     

 

slideshow

       
 
Visitor Videos
 
       
 

Share your video of this arachnid.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Attach a video, a YouTube link, or a cloud storage link.
 
 

 

 
     
     
       
       
 
Other Videos
 
     
     
     

 

Camcorder

 
 
Visitor Sightings
 
           
 

Report a sighting of this arachnid.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Be sure to include a location.
 
  Alfredo Colon
8/13/2019

Location: Woodbury, MN

slow running crab spider  
           
 
MinnesotaSeasons.com Sightings
 
 

 

 

 

 

Binoculars


Created: 12/23/2021

Last Updated:

About Us | Privacy Policy | Contact Us | © 2022 MinnesotaSeasons.com. All rights reserved.