Under this head one might arrange nearly the whole of our moths, except, perhaps, a little species, the Euzephora eoccidivora, which Professor Comstock has discovered to be predaceous, and to live upon plant-lice in the larval state, and one or two others, which, perhaps, have similar habits. A good many species become unusually numerous, however, in certain years and localities. Almost always this seems to be owing to the temporary cessation of action of the checks which keep down species from excessive multiplication, and disturbing the order of things. When we cultivate a large quantity of any cereal or plant of economic value, we in effect afford abundant food for the insects which habitually infest it. Many will recollect that the maple and other shade trees in Brooklyn and New York used to be completely defoliated by the middle of summer by the common Brown Drop or Measuring Worm, Eudalimia subsignaria. The English sparrow rid us of this nuisance; it eat every one of them. This Measuring Worm sought refuge in the cities from the birds which attacked it, and kept it down in the country. In the cities the birds were less plentiful and, this check being removed, they throve exceedingly.