We have here an example of the direct relation of cause to effect, although I am not in a position to assert that the effect is always produced in the same way.  To me there is no question as to the fact that the constitution of those insects which nature has accorded the faculty of liberating is strengthened, and that their chances of life are increased, if the cold of winter is intense enough to plunge them into an absolute rest, and is not unseasonably affected by warm, spring-like days.  It is certain that such cold is capable of contributing largely to the multiplication of the individuals of such species as hibernate in the egg state, and it also has a beneficent influence upon those species which, like the small social larvae, pass this season upon the earth enveloped in a silken envelope, or, like the larvae of the Noctuellae, between dead leaves or upon the ground itself.

On another hand, it cannot be doubted that mild winters greatly contribute to the bringing about of a destruction of larvae and chrysalids in two ways:  First, they favor the development of mould, which, as well known, attacks the larvae of insects when these have been enfeebled by an excess of rain or dampness; and second, they permit beasts of prey to continue to exercise their activity.  Now, these latter are numerous.  Moles, instead of burying themselves deeply, then continue to excavate near the surface, and shrew mice are constantly in search of food.  These small mammals, which abound in this district, destroy a large number of chrysalids of Lepidoptera.

It is the same with birds.  As soon as severe cold begins to prevail in the north and east, they come in troops to the open fields and the sheltered slope of the hills of our district.  But it is scarcely worth while to stop to tell of the skill and perseverance of these destroyer of larvae.  We may mention, the woodpecker, however, as a skillful searcher for insects that lie hidden in places where the sun has melted the snow.  The carnivorous Coleoptera and the Forficulae are likewise generally in motion during mild winters.  Doubtless these last-named do not make very large inroads in the ranks of larvae and chrysalids every day; yet, having no other food, they destroy a goodly number of them.  But I believe that the devastations made in the army of insects by all these enemies united do not equal those made by certain crustaceans—­the wood lice.

During mild winters these pests multiply, eat, and prosper out of bounds, and to such a point that, in a climate like ours, they become a true scourge that prevails everywhere, out of doors and within.  Once in a place, they begin to look for larvae and chrysalids, which they devour.  The severe cold seems to have destroyed a certain number of them, since they are now not so numerous by far; and it has at least certainly put a stop to their devastations at an epoch when the larvae are more particularly exposed to the attacks of their enemies.  It is to this