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.  And it is of interest to note that this somewhat degraded type of larva is remarkably constant through a great series of families—­gall-flies, ichneumon-flies, wasps, bees (fig. 18), ants—­that vary widely in the details of their structure and in their habits and mode of life.  Almost without exception, however, they make in some way abundant provision for their young.  The feeble, helpless, larva is in every case well sheltered and well fed; it has not to make its own way in the world, as the active armoured larva of a ground-beetle or the caterpillar of a butterfly is obliged to do.

[Illustration:  Fig. 18.  Young Larva (FL), Full-grown Larva (SL) and Pupa (N) of Hive-bee (Apis mellifica). co, cocoon; sp, spiracles; ce, eye; an, feeler; m, mandible; l, labium.  Magnified 4 times.  After Cheshire, Bees.]