Fig. 67.
As spiders grow larger, they have to moult from time to time. This process is shown by Wilder in [Figs. 66, 67]; and I have seen the same operation in Argiope. The spider hangs herself by a thread from the spinnerets to the centre of the web. The skin cracks around the thorax, just over the first joints of the legs; and the top part falls forward, being held only at the front edge. The skin of the abdomen breaks irregularly along the sides and back, and shrinks together in a bunch. The spider now hangs by a short thread from the spinnerets, and works to free her legs from the old skin, [Fig. 66]. This takes about quarter of an hour; and then she drops down, hanging by her spinnerets like a wet rag, [Fig. 67].
If struck while in this condition, she can do nothing, not even draw her legs away. After ten or fifteen minutes, the legs begin to strengthen; and she draws them gradually up toward her, works them up and down a few times, and is soon able to get into the web again.
Blackwall observed nine moults in Tegenaria civilis, a spider that lives several years. Many species, and among them some of the largest, live only one year, hatching in the winter, leaving the cocoon in early summer, and laying eggs and dying in autumn. Other species seem to require two years for their growth; hatching in summer, passing their first winter half grown, growing up the next summer, but laying no eggs till the second spring. Some species are found adult at all seasons, and may live several years.
After spiders have passed their second moult, they usually live in the same places, and follow the same habits, as the adults.
The running spiders live usually on the ground, often near water, but some kinds in the hottest and dryest places. A few species live near water, and are accustomed to run about on its surface, without becoming wet. The Theridiidæ almost all live in the shade, and always upside down in their webs. Some species live always in caves; and one in the deepest part of the Mammoth Cave has no eyes. Some spiders live only on high mountains, never appearing below the tree line. Some species seem to prefer certain kinds of plants. The horizontal branches of spruces, for instance, are particularly convenient for the webs of some species of Theridion. The water-spider, that builds its nest and lives on water-plants, has been already mentioned, and also the Argyrodes, that makes its home in the webs of other spiders. During winter immense numbers of spiders that have spent the summer under stones, in webs, and on plants, hide away among fallen leaves, and there live through the coldest and wettest weather, ready to move on the first warm day. During a thaw they often come out on the snow in great numbers.
Several house spiders have probably been imported, like rats, and are found all over the world; while other most common species never spread beyond the countries where they are most abundant.