tuberculated crab spider

not listed

NNR - Unranked

not listed

Tuberculated crab spider is a medium-sized octopus spider. It occurs across the United States and southern Canada. It is common east of the Great Plains and it occurs in California but is otherwise rare in the west. It is common in Minnesota. It is found on stems and twigs of plants in fields, meadows, and gardens.

Females are 3⁄16″ to ¼″ (4.5 to 7.0 mm) in length with a legspan of ⅜″ to ⅝″ (10 to 15 mm). Males are much smaller, ⅛″ to 3⁄16″ (3 to 5 mm) in length.

The front part of the body (cephalothorax) is greatly elongated. strongly convex above, and smoothly rounded on the sides. It is dark brown with a tan stripe in the middle, scattered black spots and light areas, and a few erect hairs. There are eight eyes arranged in two curved rows of four. The lateral eyes are larger than the median eyes and are on separate large raised bumps (tubercles). The posterior median eyes (PME) are larger than the anterior median eyes (AME). The median ocular area (MOA), the area defined by the middle four eyes, is wider than long. The facial plate above the mouth (clypeus) is strongly sloping, nearly vertical.

The abdomen is longer than wide, broadly angled beyond the middle on the lateral margins, and sharply angled at the rear. This is the feature that gives the spider the first part an alternate common name, angled crab spider. The upper surface is dull brown mottled with white specks. There is a pale longitudinal stripe in the middle and there are rows of dark chevrons toward the rear. The abdomen is highest in the rear and there is a conspicuous, large tubercle near the end. The tubercle is much larger on the female than on the male. This is the feature that gives the spider the first part of its common name. When viewed from the side the spider looks like a bud or the stump of a broken leaf stalk (petiole).

The legs are pale brown and are densely speckled with black. The first two pairs of legs are much longer than the third and fourth pairs, and are held out forward or to the side. When held to the side (laterigrade), the spider is able to move quickly sideways, like a crab. This is the feature that gives the family its common name. The last leg segment (tarsus) on each leg has two claws at the end and just a single long sensory hair (trichobothrium). The claws are not visible to the naked eye. The tarsi on the first and second pairs of 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.

Female Body Length: 3⁄16″ to ¼″ (4.5 to 7.0 mm)

Male Body Length: ⅛″ to 3⁄16″ (3 to 5 mm)

Legspan: ⅜″ to ⅝″ (10 to 15 mm)

Fields, meadows, and gardens

When hunting, the spider often clings to a stem or twig with its first and second pairs of legs straight out in front and its third pair clasping the stem or twig. In this position, with its cryptic coloration and uniquely shaped abdomen, it is well camouflaged and difficult to see.

Spiderlings overwinter in the second-to-last development stage (penultimate instar).

Sources

24, 29, 30, 82.

here is a photo I took of it outside on my sister inlaw’s house and I put it on something to get a better photo

Location: Shelby, Al

here is a photo I took of it outside on my sister inlaw’s house and I put it on something to get a better photo

Location: Albany, NY

Location: Woodbury, MN

Location: Woodbury, MN