{142}Much has been written about the mode in which the variety of forms of a single species of ant is produced. As to this there exists but little actual observation or experiment, and the subject has been much complicated by the anxiety of the writers to display the facts in a manner that will support some general theory. Dewitz was of opinion that workers and queens of ants were produced from different kinds of eggs. This view finds but little support among recent writers. Hart in recording the results of his observations on the parasol ant (of the genus _Atta_)—one of the species in which polymorphism is greatest—says[58] that these observations prove that "ants can manufacture at will, male, female, soldier, worker or nurse," but he has not determined the method of production, and he doubts it being "the character of the food." There is, however, a considerable body of evidence suggesting that the quality or quantity of the food, or both combined, are important factors in the treatment by which the differences are produced. The fact that the social Insects in which the phenomena of caste or polymorphism occur, though belonging to very diverse groups, all feed their young, is of itself very suggestive. When we add to this the fact that in ants, where the phenomena of polymorphism reach their highest complexity, the food is elaborated in their own organs by the feeders that administer it, it appears probable that the means of producing the diversity may be found herein. Wasmann has pointed out that the ants'-nest beetle, _Lomechusa_, takes much food from the ants, and itself destroys their young, and that in nests where _Lomechusa_ is abundant a large percentage of ergatogynous forms of the ants are produced. He attributes this to the fact that the destruction of the larvae of the ant by the beetle brings into play the instinct of the ants, which seek to atone for the destruction by endeavouring to produce an increased number of fertile forms; many ergatogynous individuals being the result. This may or may not be the case, but it is clear that the ants' instinct cannot operate without some material means, and his observation adds to the probability that this means is the food supply, modified either qualitatively or quantitatively.