insects which produced a given result with least labor to themselves, an established instinct. Further questions may be now asked: Why is it that any other insects besides neuters have been produced? As they can not propagate their kind, how have they become gifted with the instincts to take care of and to feed the young, provide food for the colony, build nests, etc.?
To the first question a sufficient reply is, that, if nothing but neuters were produced, there would be no insects. The other questions may be answered by an amplification of a statement already made. Neuters, as a rule, are sterile females; the exceptions to this will be considered further on; they inherit the instinct of females and perform their duties with the one exception of ovulation. To give a few details: Originally there were no neuters; and as females were numerous, each female would lay comparatively few eggs. How the neuters arose we have already seen; at first they were few, gradually increasing until they equaled and finally outnumbered the females. At the same time the labors of the female became more restricted; as they decreased in number they must, in order to keep up the colony, lay more eggs: as a result, the extra time devoted to ovulation was so much time taken from cell-building, nursing, etc. Applying this theory to facts, we can see why with the increase of neuters the duties of the queen-bee have grown less and less until they consist of nothing but ovulation. The queen-bee is a queen only in name, receiving just such extra care that her time may be entirely devoted to propagating the species. At such time when each hive only contained one reigning queen, this female had to assume the reproductive functions of her twenty thousand sterile sisters, and it is not strange that she has no time to build or to feed the young. Under no other conditions could she lay her two thousand to three thousand eggs a day. The case of the termites or so-called white ants is more striking, the female laying eighty thousand eggs in the course of a day, or very nearly one egg a second continuously. What other duties can this huge animated egg-sac perform?
With existing social insects, as a rule, the male does little or no work but that of fertilizing the females, but before the appearance of neuters we may suppose he had other duties. With many beetles the male performs a large share of the labor; the male of the burying beetle, for example, excavating the grave in which its prey is buried and in which the female deposits her eggs. With many insects the male defends the nest or burrow from the attacks of invaders, of which take an example quoted by Mr. Darwin in his "Descent of Man": "The two sexes of Lethrus cephalotes (one of the Lamellicorns) inhabit the same burrow. If during the breeding season a strange male attempts to enter the burrow, he is attacked; the female does not remain passive, but closes the mouth of the burrow and encourages her mate by continually pushing him from behind." That males are not always
