Sheetweb weavers are small, dark, shiny spiders that build interesting webs. They are less then 8 mm long. Like all spiders they have two body-segments, a cephalothorax in front and an abdomen behind. They have eight legs, all attached to the cephalothorax. On the front of the cephalothorax are the fangs, the eyes, and two small "mini-legs" called pedipalps. The pedipalps are used to grab prey, and in mating, and are much bigger in male spiders than in females. Sheetweb spiders have eight eyes in two rows of four. They have fangs that they use to bite their prey with, and venom glands. On their fangs are rough spots that they can rub together to make sounds.
It is impossible for us to tell the difference between a sheetweb weaver and a cobweb weaver except by looking at their webs (see below for more on sheetwebs).
Sheetweb weavers are one of the biggest families of spiders in the world, and they are found all around the world. There are at least 60 species in Michigan, and probably more that are not yet known.
Sheetweb weavers are found in all kinds of habitats: anywhere there are small insects and at least a little vegetation to build their webs on.
These spiders hatch from eggs, and the hatchlings look more or less like grown-up spiders, though sometimes their colors change as they age. To grow they have to shed their exoskeleton, which they do many times during their lives.
These little spiders probably don't live much longer than a year.
Most species in this family are active at night, and spend most of their lives near their webs. They are not social, coming together only to mate.
These spiders have special structures on their fangs that they can rub together to make sounds to communicate with. They probably also use web vibrations, and certainly use taste and smell to communicate.
Spiders in this family spin small horizontal sheets of webbing, or domes (see the pictures for an example). They hang upside-down underneath the web, and when a small insect or other animal walks across it, they bite through the silk, then grab their prey and pull it through to eat it.
Sheetweb weavers hide underneath their webs, and sometimes make two layers of web and hide between them for protection. If disturbed by a larger animal they quickly drop down into nearby vegetation to get away.
These are harmless little spiders that might help keep the population of small insects under control, but don't have any strong direct effects on humans.
No sheetweb weavers are known to be in danger, but there are still many species out there we don't know anything about.
The common name of this family comes from the kind of web they weave (see What Do They Eat). Some species in this family make their webs in the footprints of large animals, including people.