red running crab spider

(Philodromus rufus vibrans)

               
Conservation Status

IUCN Red List

not listed

red running crab spider

 

NatureServe

NNR - Unranked

Minnesota

not listed

Occurrence

Fairly common

Season

 

Habitat/Host

Coniferous and deciduous trees and shrubs; in or on buildings

Size

Female Body Length: 3 16 (3.75 mm)

Male Body Length: (3.40 mm)

Legspan: to ¾

Photo by Alfredo Colon

Identification

Running crab spider (Philodromus rufus) is relatively small, hairy, and drably colored. It is widely distributed across Europe, the United States, and Canada. Red running crab spider (Philodromus rufus vibrans) is the smallest of three North American subspecies. It is found on coniferous and deciduous trees and shrubs, and often in or on buildings. Females are 3 16 (3.75 mm) long and have a legspan of to ¾. Males are slightly smaller, (3.40 mm) in length.

The covering (carapace) of the front part of the body (cephalothorax) is about as long as wide, is somewhat flattened, and has smoothly convex lateral margins. It is yellowish-brown and is covered with shiny hairs. The pale upper middle (median) area is yellowish-orange and speckled with tiny brown spots. The lateral areas are yellowish-brown with a dense covering of fine brown spots and narrow black streaks.

The head is slightly angled upward. The eight eyes are black and are arranged in two rows of four each. The four eyes in the front row are all equal in size. In the back row, the middle (median) eyes are closer to the lateral eyes than they are to each other.

The abdomen is flattened, is somewhat angular at the sides, and covered with hairs. The hairs on the carapace and abdomen are soft, not erect. On the female, the pale median area is yellowish with dark brown markings. The lateral areas are brownish. There is a brown median stripe on the front (anterior) half, and a pair of brown oblique stripes on the rear (posterior) half. The male is much darker and shows less patterning.

The legs are long, slender, yellowish, and speckled with fine brown to black spots. They are optimized for lateral movement. The second pair is slightly longer than the others, which are about equal in length and thickness. 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.

 
Similar
Species

 


Food

 

 
Life Cycle

The female spins a nursery web for its eggs in the summer. It guards the web until the young spiderlings have dispersed. The last stage (instar) spiderling overwinters.

 
Behavior

This spider does not produce a web to catch prey. It hunts actively, running after prey, and passively, lying in wait and ambushing prey. It is very fast and difficult to see.

During courtship, the male rapidly vibrates its front legs.


Distribution Distribution Map   Sources: 24, 29, 30.

Comments

 


Taxonomy

Order:

Araneae (spiders)

 

Suborder:

Araneomorphae

 

No Rank:

Entelegynae (eight-eyed spiders)

 

No Rank:

RTA clade

 

No Rank:

Dionycha

 

Family:

Philodromidae (Running Crab Spiders)

 

Genus:

Philodromus

 

Section:

rufus group

 
Synonyms

Philodromus pictus

Philodromus vibrans

 
Common
Names

red 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. In crustaceans, it covers the cephalothorax.

 

Cephalothorax

The front part of a spider’s body, composed of the head region and the thoracic area fused together. Eyes, legs, and antennae are attached to this part.

 

Instar

The developmental stage of arthropods between each molt; in insects, the developmental stage of the larvae or nymph.

 

 

       

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Alfredo Colon


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Alfredo Colon
6/10/2018

Location: Woodbury, Minnesota

red running crab spider


     
     
 

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