the food-supply is cut off in winter, and all those beetles of the latest summer brood that survive hibernate in some sheltered spot, waiting for the return of spring, that they may lay their eggs, and start the life-cycle once again.  Among the Diptera, most species pass the winter as pupae, the sheltering puparium being a good protection against most adverse conditions, or as flies.  But where there is a prolonged parasitic larval life, as with the bot- and warble-flies, the maggot, warm and well-fed within the body of its mammalian host, affords an appropriate wintering stage.

Among the Hymenoptera an especially interesting seasonal life-cycle is afforded by the alternation of summer and winter generations in many Gall-flies (Cynipidae) as H. Adler (1881, 1896) demonstrated for most of our common species.  The well-known ‘oak-apples’ are tenanted in summer by grubs, which after pupation develop into winged males and wingless females.  The latter, after pairing, burrow underground and lay their eggs in the roots, the larvae causing the presence there of globular swellings or root-galls within which they live, pass through their transformations and develop into wingless virgin females.  These shelter until February or March in their underground chambers, then climb up the tree and lay on the shoots eggs, from which will be hatched the grubs destined to grow within the oak-apples into the summer sexual brood of flies.

The Lepidoptera afford examples of hibernation in all stages of the life-history.  In this order a few large moths with wood-boring caterpillars, the ‘Goat’ (Cossus) for example, undergo a development extending over several years, while at the other extreme a few small species may have three or more complete cycles within the twelve months.  But in the vast majority of Lepidoptera we find either one or two generations, definitely seasonal, within the year; the insect is either ‘single-brooded’ or ‘double-brooded.’

Almost every winter one or more letters may be read in some newspaper recording the writer’s surprise at seeing on a sunny day during the cold season, one of our common gaily-coloured butterflies of the Vanessa group, a ‘Tortoiseshell’ or ‘Red Admiral,’ flitting about.  Surprise might be greater did the observers realise that the imaginal is the normal hibernating stage for these species.  Emerging from the pupa in late summer or autumn, they shelter during winter in hollow trees, under thatched eaves, in outbuildings or in similar situations, coming out in spring to lay their eggs on the leaves of their caterpillars’ food-plants.  The larvae feed and grow through the early summer months, in the case of the Small Tortoiseshell (Vanessa urticae) pupating before midsummer and developing into a July brood of butterflies whose offspring after a late summer life-cycle, hibernate; while for the larger species of the group there is, in our islands, only one complete life-cycle in the year, though the same