According to Pennsylvania State University's College of Agricultural Sciences, one of the most common spiders in the state is the grass spider. Female grass spiders grow up to 10 to 20 millimeters, while males reach lengths of 9 to 18 millimeters. Grass spiders in the Pittsburgh area are found on their webs, which are built within residential backyards, parks and gardens. These spiders construct a horizontal, sheet-like web with a funnel attached to its side. Grass spiders are brown and they feature thin lines on their cephalothorax and abdomen. This spider is active in Pittsburgh from spring to fall, but adult grass spiders usually do not survive the winter.
Long-bodied cellar spiders are also known as "daddy long legs" spiders and occupy many household basements in Pittsburgh. These spiders are different from Harvestmen, which are arachnids that are also known as daddy long legs. Long-bodied cellar spiders receive their name from their slender abdomens and primary habitats, house cellars. The length of long-bodied cellars range from 6 to 8 millimeters. Long-bodied cellar spiders bounce on their webs to confuse their prey and potential predators; the bouncing causes these spiders to appear like a blur. The scientific name for the long-bodied cellar spider is Pholcus phalangioides.
Two black widow spider species live in the greater Pittsburgh area: the southern black widow and (much less commonly) the northern black widow.The females of both species are approximately 8 to 13 millimeters in length. Females are larger than males, which are only 4 to 6 millimeters. Also, males do not have enough venom to cause harm to humans, but female black widows are considered dangerous due to their high level of venom. In Pittsburgh, black widows are found in dimly lit areas such as basements, attics and dark crevices in parking garages. These spiders may be identified by the red hourglass-shaped marking on their abdomen.
Orb weavers are spiders that weave round, orb-shaped webs; however, the center of their webs have zigzag patterns. The abdomens of these spiders are abnormally larger than their heads and cephalothoraxes. Pittsburgh is home to the yellow garden spider, cross orb weaver and marbled orb weaver. The females of all three orb weavers are approximately 6.5 to 20 millimeters, and the males are 5.5 to 13 millimeters long. Cross orb weavers are brown with a white cross marking on their abdomen, while marbled orb weavers are yellow and burnt orange. Yellow garden spiders are yellow and black. Orb weaver webs may be found on fences, river beds and the sides of buildings.