Pupipara.  Still more astonishing is the mode of reproduction in the allied family of the Termitoxeniidae, curious, degraded, wingless ‘guests’ of the termites, or ‘white ants,’ lately made known through the researches of E. Wasmann (1901).  Here the individual is hermaphrodite—­a most exceptional condition among insects—­and lays a large egg, whence is usually hatched a fully-developed adult!  Here then we find that all the early stages, usual in the higher insects, are omitted from the life-story.

Interesting comparison may be made between the total duration of various insect life-stories.  To some extent at least, the length of an insect’s life is correlated with its size, its food, the season of the year when it breeds.  Small insects have, as a rule, shorter lives than large ones; those whose larvae devour highly nutritive food generally develop more quickly than those which have to live on dry, poor, substances; life-cycles follow one another most rapidly in summer weather when temperature is high and food plentiful.

In early chapters we have already noticed the long aquatic life of the larva and nymph of a dragon-fly, relatively a large insect, and the rapid multiplication of the repeated summer broods of virgin aphids (p. 18).  Within the one order of the Coleoptera it is instructive to compare the small jumping leaf-beetles, the ‘turnip-flies’ of the farmer, whose larvae mine in the green tissues, and complete their transformations so rapidly that several successive broods appear in the spring and early summer, with the larger click-beetles whose larvae, the equally notorious ‘wireworms,’ feed on roots for three or four years before they become fully grown.  Among the Diptera, the ‘leather-jacket’ grub of the crane-fly, feeding like the wireworm on roots, has a larval life extending through the greater part of a year, while the maggot of the bluebottle, feeding on a rich meat diet, becomes mature in a few days.  As examples of excessively long life-cycles the ‘thirteen-year’ and ‘seventeen-year’ cicads of North America, described by C.L.  Marlatt (1895), are noteworthy.  Certain specially populous ‘broods’ of these insects are known and localised, so that the appearance of the imagos in future years can be accurately predicted.  Here again we have to do with bulky insects whose subterranean larvae and nymphs feed on comparatively innutritious roots.

In our own climate, it is of interest to notice the variation among insects as to the stage which carries the race over the winter.  The click-beetles, mentioned just above, emerge from their buried pupae in summer, hibernate under stones or clods, and lay eggs among the herbage next spring.  At the same time of course, owing to the extended term of the larval life, many more individuals of the species are wintering underground as ‘wireworms’ of various ages, and these, except in very severe frosts, can continue their occupation of feeding on roots.  But in the case of the ‘turnip-flies’