Spiders, Pacific Northwest
Flat-bellied ground spiders are part of the 7th largest spider family in the world, comprising over 2,000 species in 8 subfamilies. and 114 genera. They range in size from 2 to 20 mm.
They are a wandering spider, found at ground level in open habitats. Some species are house spiders, but most prefer to live outdoors. They build funnel-type webs, where they spend their days, and then hunt at night.
The female will hide her papery egg sac in small holes under logs, stones & other types of debris, and will guard it until the eggs hatch.
These spiders are rather stout, with a flattened, elongated abdomen. The carapace is ovoid and rather low, with a smooth body in most species.
Flat-bellied ground spiders have 8 eyes in 2 rows. The posterior medial eyes are often not round, but oval, and are sometimes reduced to slits. All eyes have a silvery sheen, except for the anterior medialis, which are dark. This spider’s sternum is also ovoid. Their legs are quite stout, and in some species, small stiff hairs cover their leg areas. The female’s palps are furnished with small spines & a finely-toothed claw.
The abdomen may sometimes feature a thick covering of short, sleek hairs, giving it a somewhat mouse-like appearance. Many species are of uniform color, usually a grayish-brown to black hue. The abdomens of some varieties, however, have striking, white patterns of spots or lines, while those of others are iridescent.