Common Name: Ground Spider
Latin Name: Gnaphosa
Common Family Name: Ground spiders
Latin Family Name: Gnaphosidae
Origin: A number of species of spiders in this genus are native to North America.
Biology: These are hunting spiders which use their silk only for lining their retreat and for creating their egg sacs. They may be very fast moving spiders and commonly enter structures to hunt for food or harborage. They are primarily nocturnal, but when found in structures may be seen walking along floors, countertops, walls, or ceilings. They are capable of biting humans, but their venom is generally not considered dangerous. The venom is a cyto-toxic venom, and may cause death of the tissues at the site of the bite, potentially leading to an open wound.
Identification: The spiders in the genus Gnaphosa are medium sized and usually dark brown to almost black in color. Their legs are moderately long and their abdomen is covered with very short hair. The top of the cephalothorax is flattened and has the appearance of a concave crease in it. There are 8 eyes arranged in two rows of four eyes, one row above the other, at the front of the cephalothorax.
Characteristics Important in Control: The occasional spider found indoors is best removed by vacuuming. Elimination of harborage sites around the exterior of the structure will help to reduce the populations of spiders nearby. This includes removing plant debris, firewood, lumber, or other objects that the spiders can hide within or under. Good sanitation and storage practices indoors, keeping materials off the floor in storage areas, will also help prevent the spiders, and exclusion from the structure by sealing cracks, holes, or other openings is needed. Pyrethroid insecticides are excellent for intercepting the spiders that move to the building foundation.