ground crab spiders
(Xysticus spp.)
Overview • Description • Distribution • Taxonomy
Overview |
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Xysticus is a 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 13 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. |
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Description |
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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 fourth 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. |
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Distribution |
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| 11/13/2022 | ||||
Taxonomy |
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| Class | Arachnida (arachnids) | ||
Order |
Araneae (spiders) | ||
Suborder |
Araneomorphae (typical spiders) | ||
| Infraorder | Entelegynae (entelegyne spiders) | ||
Superfamily |
Thomisoidea (crab and running crab spiders) | ||
Family |
Thomisidae (crab spiders) | ||
The ranking of spiders between Family and Order is controversial and is often omitted when displaying the taxonomy of spiders. The Opisthothelae was recently created to exclude the Mesothelae, which display more primitive characteristics. Opisthothelae is sometimes treated as a suborder, sometimes as an unranked clade. iNaturalist does not recognize the reordering. The order shown above follows iNaturalist. |
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Subordinate Taxa |
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Alberta ground crab spider (Xysticus albertensis) boreal ground crab spider (Xysticus canadensis) contrasted ground crab spider (Xysticus alboniger) elegant crab spider (Xysticus elegans) Emerton’s crab spider (Xysticus emertoni) Great Plains ground crab spider (Xysticus acquiescens) grey ground crab spider (Xysticus gulosus) ground crab spider (Xysticus acerbus) helpful ground crab spider (Xysticus benefactor) punctated ground crab spider (Xysticus punctatus) rare ground crab spider (Xysticus fervidus) recumbent ground crab spider (Xysticus auctificus) swollen ground crab spider (Xysticus ampullatus) tan crab spider (Xysticus ferox) three-banded crab spider (Xysticus triguttatus) twisted ground crab spider (Xysticus luctans) wandering ground crab spider (Xysticus discursans) |
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Synonyms |
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Common Names |
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ground crab spiders |
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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.
Chelicerae
The pair of stout mouthparts, corresponding to jaws, in arachnids and other arthropods in the subphylum Chelicerata.
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.
Visitor Photos |
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Alfredo Colon |
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Babette Kis |
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Xysticus with Harmonia axyridis prey Barnes Prairie 10 6 2020 |
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Barnes Prairie, Racine Co WI Xysticus on Canada goldenrod 9 21 2020 |
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Xysticus ground crab spider Eurasian ladybird beetle |
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Xysticus, species cannot be ID'd positively without dissection Thought you might be interested in this little Xysticus, photographed June 26, 2022 at Barnes Prairie, Racine Co., WI. In less than five minutes, I got over 80 pics, of which 20 were decent. I've attached 4 pics showing the sequence of a male approaching a female, climbing over her, and mating. I've gotten many photos of these spiders in past years, but this is the first time I've gotten the entire sequence of a male approaching a female, up to mating. |
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Male Xysticus approaches female from below
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Male Xysticus with legs over female |
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Male Xysticus climbing over female's back Barnes Prairie Racine Co. June 2022 |
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Xysticus male and female success at last |
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Alfredo Colon |
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MinnesotaSeasons.com Photos |
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Slideshows |
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| Ground Crab Spiders (Xysticus) Andree Reno Sanborn |
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| Xysticus Lloyd Davies |
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About
Xysticus crab spider |
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Visitor Videos |
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Share your video of this arachnid. |
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| This button not working for you? Simply email us at info@MinnesotaSeasons.com. Attach a video, a YouTube link, or a cloud storage link. |
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Other Videos |
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| Ground Crab Spider (Xysticus sp.). Species identification can be difficult. Lifers Earth |
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About
Sep 17, 2022 |
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Visitor Sightings |
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Report a sighting of this arachnid. |
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| This button not working for you? Simply email us at info@MinnesotaSeasons.com. Be sure to include a location. |
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Alfredo Colon |
Location: Albany, NY |
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| Alfredo Colon 8/10/2022 |
Location: Albany, NY |
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| Alfredo Colon 8/8/2022 |
Location: Albany, NY |
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| Alfredo Colon 8/7/2022 |
Location: Albany, NY |
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| Alfredo Colon 8/2/2022 |
Location: Albany, NY |
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| Babette Kis 6/26/2022 |
Location: Barnes Prairie, Racine County, WI Thought you might be interested in this little Xysticus, photographed June 26, 2022 at Barnes Prairie, Racine Co., WI. In less than five minutes, I got over 80 pics, of which 20 were decent. I've attached 4 pics showing the sequence of a male approaching a female, climbing over her, and mating. I've gotten many photos of these spiders in past years, but this is the first time I've gotten the entire sequence of a male approaching a female, up to mating. |
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| Babette Kis 10/6/2020 |
Location: Barnes Prairie, Racine County, WI Xysticus with Harmonia axyridis prey Barnes Prairie 10 6 2020 |
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| Babette Kis 9/21/2020 |
Location: Barnes Prairie, Racine County, WI Barnes Prairie, Racine Co WI Xysticus on Canada goldenrod 9 21 2020 |
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MinnesotaSeasons.com Sightings |
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Created: 11/13/2022
Last Updated: