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.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.
an animal that mainly eats meat
mid-altitude coastal areas with mild, rainy winters and long, dry summers. Dominant plant types are dense, evergreen shrubs.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
fertilization takes place within the female's body
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Climbing plants are also abundant. There is plenty of moisture and rain, but may be somewhat seasonal.
scrub forests develop in areas that experience dry seasons.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
this biome is characterized by large expanses of coniferous forest, there is an extended cold season and heavy snowfall.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome found in very cold places -- either close to polar regions or high on mountains. Part of the soil stays frozen all year. Few kinds of plants grow here, and these are low mats or shrubs not trees. The growing season is short.