(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' 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