three-banded crab spider

(Xysticus triguttatus)

Conservation Status
IUCN Red List

not listed

NatureServe

NNR - Unranked

Minnesota

not listed

 
three-banded crab spider
Photo by Babette Kis
 
Description

Three-banded crab spider is a common, small, ground crab spider. It occurs throughout the United States and southern and central Canada. Adults are most active from May to July, but females have been trapped as late as September. They are found in woodlands, fields, meadows, and bogs. Unlike most Xysticus species, they live on low plants and on grasses.

Adults are small, hard-bodied, bristly, and crab-like in appearance. Males and females are very different in both size and appearance. The female is to ¼ (4 to 6 mm) in length. The male is much smaller, to 316 (3.5 to 5.0 mm) in length. The legspan ranges from ½ to 1116 (12 to 18 mm).

The plate (carapace) covering the front part of the body (cephalothorax) is moderately high, slightly longer than wide, and smoothly rounded on the sides when viewed from above. When viewed from the side it is slightly convex, highest near the front, then dropping down toward the back near the base of the third pair of legs. The rear of the carapace is overhung by the abdomen.

There are eight eyes arranged in two curved rows of four. The front (anterior) row is curved forward and the rear (posterior) row is curved backward. The lateral eyes are larger than the median eyes and are on low raised projections (tubercles). The anterior median eyes (AME) are closer to the anterior lateral eyes (ALE) than to each other. The posterior median eyes (PME) are closer to each other than to the posterior lateral eyes (PLE). The median ocular area (MOA), the area defined by the middle four eyes, is broader than long and slightly narrowed in front. The plate on the face above the mouth (clypeus) is armed with several long spines. The jaws (chelicerae) are small and have no teeth.

On the female, the carapace is brownish yellow. Near the rear margin there is a small round spot in the middle (median spot) and a similar spot on each side (lateral spots). An indistinct black stripe extends forward from each lateral spot toward the eye area. On each side, a whitish line extends backward from between the PME and PLE, joining in a broad arc at the median spot. The area around the eyes is pale.

The abdomen is large, broadly oval, widest toward the rear, and flattened above. It is mostly yellowish to almost white, with several small, round, black spots. There is a pair of spots at the base, a rearward curved band of four spots in the middle, and a forward curved band of four spots at the rear. This is the feature that gives the species its common name.

The legs are long, stout, and brownish yellow with dark brown flecks. The first and second pairs of legs are the longest. They are strong, spiny, and nearly equal in length. They are normally held out and forward, like a crab. This is the feature that gives the family Thomisidae its common name. The third and fourth pairs are shorter and nearly equal in length. On the first pair, the third segment (femur) is slender and about four times longer than wide, and the fifth segment (tibia) has 3 or 4 pairs of stiff hairs on the upper side. The last leg segment (tarsus) on each leg has two claws at the end but these are not visible without magnification. The tarsi on all legs do not have a brush of hairs (scopula) on the underside, and there is no tuft of hairs (claw tuft) at the end on any leg.

On the male, the carapace and the femurs on the first and second pairs of legs are much darker. The abdomen is much more heavily marked with more black spots on the front half, black bands on the rear half, and a black median stripe.

 

Size

Female Body Length: to ¼ (4 to 6 mm)

Male Body Length: to 316(3 to 5 mm)

Legspan: ½to 1116 (12 to 18 mm)

 

Web

No web
 

Similar Species

 
Habitat

 

Biology

Season

May to July

 

Behavior

Adults are slow moving, and they rely on ambush to capture their prey.

When the legs are held out to the side the spider is able to walk forward, backward, or sideways (laterigrade).

The female does not build webs, snares, or retreats. To protect its egg sac it will fold over the edge of a leaf and secure it with silk.

 

Life Cycle

 

 

Food

Insects and other spiders

Distribution

Distribution Map

 

Sources

24, 29, 30, 82, 83.

9/13/2024    
     

Occurrence

Common

Taxonomy

Class

Arachnida (arachnids)

Order

Araneae (spiders)

Suborder

Araneomorphae (typical spiders)

Infraorder

Entelegynae

Superfamily

Thomisoidea (crab and running crab spiders)

Family

Thomisidae (crab spiders)

Subfamily

Thomisinae

Tribe

Coriarachnini

Genus

Xysticus (ground crab spiders)

   

Subordinate Taxa

 

   

Synonyms

Xysticus feroculus

   

Common Names

threebanded crab spider

three-banded crab spider

three-banded ground crab spider

thrice-banded 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.

 

Clypeus

On insects, a hardened plate on the face above the upper lip (labrum).

 

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.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.

 

Tubercle

On plants and animals: a small, rounded, raised projection on the surface. On insects and spiders: a low, small, usually rounded, knob-like projection. On slugs: raised areas of skin between grooves covering the body.

 

 

 

 

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Babette Kis

three-banded crab spider   three-banded crab spider

Xysticus triguttatus

Xysticus triguttagus, female (white, on top) and male (under); photos were taken at Barnes Prairie, Racine Co., WI on July 2, 2023.

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Xysticus triguttatus (Crab Spider)
Allen Chartier

Xysticus triguttatus (Crab Spider)

 

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Babette Kis
7/2/2023

Location: Barnes Prairie, Racine Co., WI

Xysticus triguttagus, female (white, on top) and male (under); photos were taken at Barnes Prairie, Racine Co., WI on July 2, 2023.

three-banded crab spider
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Created: 9/13/2024

Last Updated:

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