curious excrescences on various trees and plants, called gulls, for the nutriment and defence of its progeny. This parasite insect discovers its secret chamber, pierces its wall, however thick, and commits the destroying egg to its offspring." In vain, also, might we add, does the sand-wasp excavate her deep cell for her young ones; for when once the ichneumon has discovered the retreat, the destruction of the young larvæ is inevitable. She pierces through the defences piled over the mouth of the cavity, with all the precision and patience of a higher creature, and rests not until she has thrust down her long ovipositor, and placed the egg in the body of the helpless prisoner below, when she flies away, confident that the days of her victim are numbered, and having thus doomed him to be eaten up alive! The common caterpillar, which, by its ravages in our cabbage rows, makes itself a little too familiar to us, has a fierce enemy in these flies; they dart upon it, pierce its body in many places, laying an egg in each wound; these in due time become hatched, and eat their way out of the body of the poor caterpillar, who soon dies, while the larvæ, after undergoing their proper transformations, become perfect insects themselves, fully equipped to proceed to the same work in some other individual of the caterpillar kind. To man, this ordinance of the Creator, that some insects should lay their eggs in the bodies of others, and so destroy them, is of inestimable benefit. It is quite impossible to imagine what would be the result, were weevils, caterpillars, and such like insects, to be permitted to multiply without a check. Produce of all kinds would soon be consumed, and the desolations of an universal famine would overwhelm man and beast. But God has been pleased to ordain it otherwise. In proportion to the increase of the destroyers is the increase of those that prey upon and destroy them. Thus, what has been well called the balance of creation is preserved, and by means of the insects in question, conjoined to other causes, is the command to the destroying powers enforced--"Hitherto shall ye come, but no farther." CHAPTER II. STRUCTURE AND CONTENTS OF THE EGG.