All spiders have two body sections: the cephalothorax in front and an abdomen behind. The abdomen contains the digestive and reproductive systems, and on the underside of it are the glands where silk is produced. The structures that produce the silk are called spinnerets.
They have eight legs, all attached to the cephalothorax. On the front of the cephalothorax are the mouth, the fangs, the eyes, and two small "mini-legs" called pedipalps. These are used to grab prey, and in mating, and are much bigger in male spiders than in females. Different species of spiders have six or eight eyes, and the size and arrangement of eyes is different in different groups. All spiders have fangs that they use to bite their prey with, and most have venom glands.
Female spiders are often much bigger than males.
Spiders are everywhere! Baby spiders are so light, they can put out a line of silk and float away on a breeze, and so they are spread around the globe. Also, spiders that live in peoples' houses often get moved around by accident when people move. Spiders are found on every continent, and there are over 40,000 species known to science. That's not all of them though, there are thousands more we don't know about yet.
Spiders survive in every habitat on land except the very coldest. There are even a few in shallow fresh water.
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. Unlike insects, some spider species keep growing after they become adults, and continue to molt as they get bigger.
After mating adult female spiders lay dozens to hundreds of eggs. The number varies among species and is affected by how well fed she is.
Female spiders often guard their eggs and young, or even carry them with them until the young have hatched and molted.
Most spider species live a year or less, but some large ones can live for several years. Usually males die soon after they mate, it's only the females that can live longer.
Nearly all spiders live as solitary hunters, only finding another of their species to mate. Many species make complicated webs to trap prey and give themselves protection. A few tropical species live in groups in really big webs.
Spiders are very sensitive to vibrations, especially in their webs. Most don't see very well, but the Jumping Spiders see very well.
All spiders are predators. They attack only live insects, other spiders, and other invertebrates. A few very large spider species attack small vertebrates like lizards, minnows, or frogs, but this is rare. Spiders are famous for trapping their prey in webs of sticky silk, but many of them are wandering predators who don't use silk to catch prey.
Spiders often have good camouflage, and many of the wandering hunter species hunt at night when big predators can't see them. Many spiders build a retreat of silk to hide in too. Some are quick runners, and will just run away if they can. These may use their silk as a safety line, jumping off into the air with a silk thread attached so they don't fall.
Spiders are major predators of insects, including many insects that are pests to humans.
Spiders scare a lot of people (usually this is unnecessary). A few spider species have venom that is dangerous to people, but spider bites are actually pretty rare. They get blamed for a lot of skin injuries that are not actually spider bites. Most spiders have such small weak fangs that they couldn't break a person's skin, even if they wanted to.
Spiders eat a lot of insects that are agricultural pests and eat our food.
George Hammond (author), Animal Diversity Web.
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.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
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.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
active at dawn and dusk
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.
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
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
Having one mate at a time.
having the capacity to move from one place to another.
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
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
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.
Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).
having more than one female as a mate at one time
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.
breeding is confined to a particular season
remains in the same area
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
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).
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.