Trap-door nests are made by spiders belonging to two widely different groups, namely the Lycosidae or wolf-spiders, to which the true tarantula belongs, and the Mygalomorphae, containing the species which construct the best-known types of this style of burrow.
In the trap-door species of Lycosidae, like, for instance, Lycosa opifex of the Russian steppes, the hinge is weak and the lid of the burrow is kept normally shut by being very much thicker and heavier at its free margin opposite the hinge so that it readily falls by its own weight.
Be that as it may, the snare in many instances, as in that of the Agalenidae (Tegenaria, Agalena), a family closely allied to the Lycosidae, is a horizontal sheet of webbing, upon which the spider runs, continuous with the lower half of the aperture of the tube, of which it is simply an extension.
More often it consists of a thick felting of silk, either spun in one continuous piece into a globular form, as in the Aviculariidae, or composed of two plate-like pieces, an upper and a lower, united at the edges and lenticular in shape, as in some of the Lycosidae.
Other species of wandering habits carry the cocoon about with them, sometimes attached to the spinnerets, as in the Lycosidae, sometimes tucked under the thorax, as in the large tropical house-spider, Heteropoda regia, one of the Clubionidae.
In these spiders, too, the newly-hatched young shift for themselves as soon as they emerge from the cocoon; in others that guard the cocoon the young stay for a longer or shorter time under their mother's protection, those of the wandering Lycosidae climbing on her back to be carried about with her wherever she goes.
Species of other families (Lycosidae, Clubionidae) may live for a few seasons, hibernating in the soil or amongst dead leaves; and examples of the larger spiders (Aviculariidae) have been kept alive in captivity for several years.
As instances of procryptic or celative coloration may be mentioned that of the species of the genus Dolomedes, one of the Lycosidae, which lives amongst reeds and is marked with a pair of longitudinal yellow lines which harmonize with the upright stalks of the vegetation, and Lycosa pitta, which lives on the sand, can scarcely be seen on account of its mottled pattern: Sparassus smargdulus and the species of Pecucetia, which are found amongst grass or low green herbage, are mostly green in colour, and Salticus scenicus is banded with white and black to match the grey tint of the rocks and stone walls on which it hunts its prey.
When concealment is no longer possible terrestrial species, like the Lycosidae, dart swiftly to the nearest shelter afforded by crevices in the soil, stones, fallen leaves or logs of wood, while those that live in bushes, like the Argyopidae, drop straight to the ground and lie hidden in the earth or in the fallen vegetation beneath.
This spider belongs to the family Lycosidae, and has numerous allies, equalling or surpassing it in size, in various parts of the world, the genus Lycosa being almost cosmopolitan in distribution.
These spiders are very much larger and more venomous than the largest of the Lycosidae, and in the Southern states of North America the species of wasps that destroy them have been called tarantula hawks.
Examples of Selenops (Clubionidae) lie flat and absolutely still on the bark of trees, to which their coloration assimilates, and spring like a flash of light upon any insect that touches their legs; the Lycosidae dart swiftly upon their prey; and the Salticidae, which compared with other spiders have keen powers of vision, stealthily stalk it to within leaping distance, then, gathering their legs together, cover the intervening space with a spring and with unerring aim seize it and bury their fangs in its body.
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