ith
clothing at the same time.

The case-forming habit of the Clothes-moth caterpillars leads us
naturally to consider the similar habit adopted by their allies the
Caddis-larvae which live in the waters of ponds and streams, for the
Caddis-flies (Trichoptera) have much in common with the more primitive
Lepidoptera. The caddis-larva is as a rule of the eruciform type, but
with well-developed thoracic legs, and with hook-like tail-appendages;
by means of the latter it anchors itself to the extremity of its curious
'house.' It is of interest to note that in the earlier stages of some
caddises lately described and figured by A.J. Siltala (1907), the legs
are relatively very long, and the larva is quite campodeiform in aspect.
Some of these caddis-grubs retain the campodeiform condition and do not
shelter permanently in cases, as their relations do. Different genera of
caddises differ in their mode of building. Some fasten together
fragments of water-weeds and plant refuse, others take tiny particles of
stone, of which they make firmly compacted walls, others again lay hold
of water-snail shells, which may even contain live inhabitants, and bind
these into a limy rampart behind which their bodies are in safe hiding.

The silk with which the 'caddis-worms' fasten together the materials for
their houses is produced from spinning-glands which like those of the
Lepidoptera open into the mouth.

The survey of the various types of beetle-larvae enumerated above (pp.
50-56) concluded with a short description of the _legless grub_, which
is the young form of a weevil or a bark-beetle. This is a larva in which
the head alone has its cuticle firm and hard; the rest of the body is
covered with a pale, flexible cuticle, so that the grub is often
described as 'fleshy.' This type of larva is by no means confined to
certain families of the beetles, it is frequently met with, in more or
less modified form, in two other important orders of insects, the
Hymenoptera and the Diptera. Among the Hymenoptera this is indeed the
predominant larval type. We have just seen that a caterpillar is the
usual form of larva among the saw-flies, but in all other families of
the Hymenoptera we find the legless grub. A grub of this order may
usually be distinguished from the larva of a weevil or other beetle, by
its relatively smaller head and smoother, less wrinkled cuticle; it
strikes the observer as a feebler, more helpless creature than a
beetle-grub.