The burrow of the young hamster is only about a foot in depth, while that of the adult descends 4 or 5 ft.
This second hole is opened the next year, and used as the ordinary entrance, so that the number of closed up holes round a burrow gives an indication of the length of time that it has been occupied.
They burrow in the sands of every shore; they throng the weeds between tide-marks; they ascend all streams; they are found in deep wells, in caverns, in lakes; in Arctic waters they swarm in numbers beyond computation; they find lodgings on crabs, on turtles, on weed-grown buoys; they descend into depths of the ocean down to hundreds or thousands of fathoms; they are found in mountain streams as far above sea-level as some of their congeners live below it.
Most earthworms live in the soil, which they devour as they burrow through it.
Another group of Hymenoptera occasionally causes much harm in fir plantations, namely, the Siricidae or wood-wasps, whose larvae burrow into the trunks of the trees and thus kill them.
Other allied African genera are Steatomys and Lophuromys, which include several species of small mouse-like rodents, with the habits of dormice generally, though some burrow in cornfields.
Some species, however, are alleged to be carnivorous, and a North American form of the genus Hydropsyche is said to spin around the mouth of its burrow a silken net for the capture of small animal organisms living in the water.
It lives on dry, welldrained ground, and digs a deep burrow lined with silk to prevent the infall of loose particles of soil.
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.
Upon hatching, the young, which differ from the adult in possessing long antennae and a pair of powerful fossorial anterior legs, fall to the ground, burrow below the surface, and spend a prolonged subterranean larval existence feeding upon the roots of vegetation.