northern yellow sac spider

not listed

NNR - Unranked

not listed

Northern yellow sac spider is an exotic, relatively small, longlegged sac spider. It is native to Europe, North Africa, the Middle East, Turkey, and central Asia. It was probably introduced into the United States in the 1940s. The first North American record is from Connecticut in the summer of 1949. Since then, it has spread rapidly. It now occurs throughout southern Canada, the United States, Mexico, and Central America. It is most common in the northeast and in major metropolitan areas. In Minnesota, it has been reported only in the Twin Cities Metro area and in Mankato. It is found on low tree limbs, on shrubs, on plant foliage, in gardens, and on buildings. More often, it is found indoors in houses and other man-made structures, especially in fall and winter.

Females are ¼″ to ⅜″ (7 to 10 mm) in length and have a ½″ to 11⁄16″ (12 to 18 mm) legspan.

The front part of the body (cephalothorax) is longer than wide. The upper part (carapace) is orangish-yellow or yellowish-green. There is no longitudinal furrow (median groove) on the carapace but there is a slightly darkened line in that area, a “false groove.”

There are eight eyes in two rows of four each. All of the eyes are about the same size. The front row is slightly curved backward. The rear row is curved forward. The eyes in each row are equally spaced, the median eyes are the same distance from the lateral eyes as they are from each other.

The jaws (chelicerae) are large, dark brown, and prominent. The forward-facing margin has three teeth, the rear-facing margin has two teeth. Each fang rests in a furrow between two ridges (margins). The lower margin has three teeth.

The abdomen is oval, longer than wide, and convex when viewed from the side. It is dull yellow or pale green with a slightly darker cardiac mark near the front but with no other markings.

The legs are long and yellow. The first pair of legs is longer than all the others. All legs have two claws at the tip. On each leg, the tip of the fifth segment (metatarsus) and sixth segment (tarsus) are black. This feature gives the spider one of its common names, "blackfooted spider".

Males are smaller, 3⁄16″ to 5⁄16″ (5.5 to 8.5 mm) in length.

Female Body Length: ¼″ to ⅜″ (7 to 10 mm)

Male Body Length: 3⁄16″ to 5⁄16″ (5.5 to 8.5 mm)

Legspan: ½″ to 11⁄16″ (12 to 18 mm)

Sac spiders do not construct hunting webs, but they will build a silken retreat and nest.

Low tree limbs, shrubs, plant foliage, gardens, and buildings, often indoors.

Indoors: year-round

Outdoors: ?

Northern yellow sac spiders are active at night. They spend the day hiding in a silken tubular retreat, the “sac” that this family is named for. When outdoors, the retreat is usually made in a folded over leaf.

When outside, adults or subadults may hibernate under leaves or in a retreat under a rock or under bark.

Small insects

Northern yellow sac spiders, like most spiders, are venomous. They are defensive and will bite humans when threatened, as when they are trapped in clothing. However, the effects of the bite are mild. The bitten area may be painful for about one hour and forty-five minutes, but it does not cause the skin around the bite to die (necrosis).

Sources

24, 29, 30, 82, 83.

Location: St. Paul Park, MN

Location: Albany, NY