Ground crab spiders

Overview

Xysticus is a very large genus of crab spiders known as ground crab spiders. There are 293 recognized Xysticus species worldwide as of November 2022 according to World Spider Catalog. There are 63 species in North America north of Mexico, and at least 14 species in Minnesota.

Xysticus are slow-moving spiders that must wait in ambush to catch their prey. They do not spin hunting webs. They are usually found on the ground or on low vegetation.

Description

Xysticus is a small to medium-sized crab spider. Females are much larger than males. Most are dark brown, reddish-brown, or gray, with pale markings.

The upper side of the front part of the body (carapace) is slightly longer than wide. When viewed from the side it is flat in front then drops off sharply at an angle near the base of the third pair of legs. This is not apparent in most photos because the front of the abdomen extends forward over the carapace at the same angle. The eyes are small and are arranged in two rows of four each. The front (anterior) outer (lateral) eyes (ALE) are larger than the rest and are on small, rounded projections (tubercles). The rear (posterior) lateral eyes (PLE) are also on tubercles which are “incompletely joined” with the tubercles of the ALE. The jaw-like mouth parts (chelicerae) are small and untoothed.

The abdomen is broadly oval, flat, and widest near the rear.

The legs are long and stout. The first and second pairs are the longest, and they are held out and forward like a crab. This allows the spider to move sideways (laterigrade). On each leg the last leg segment (tarsus) has two claws at the tip, though these are not visible without magnification. On the front legs the third segment (femur) is slender and about four times as long as wide, and the fifth segment (tibia) has three or four pairs of spines on the lower surface.

Distribution

Sources

24, 30, 82, 83.

Xysticus C. L. Koch, 1835 in Bánki, O., Roskov, Y., Döring, M., Ower, G., Hernández Robles, D. R., Plata Corredor, C. A., Stjernegaard Jeppesen, T., Örn, A., Pape, T., Hobern, D., Garnett, S., Little, H., DeWalt, R. E., Miller, J., Orrell, T., Aalbu, R., Abbott, J., Abreu, C., Acero P, A., et al. (2026). Catalogue of Life (2026-08-26 XR). Catalogue of Life Foundation, Amsterdam, Netherlands. https://doi.org/10.48580/dgyy9