With the ants we conic to a more complicated social life. Here not only do great numbers of separate individuals live together and adopt dif ferent functions, according to the positions which they occupy in the colony, but these individuals are also greatly modified in structure, and in their physiological processes. in such ways as to fit them especially for the parts they have to play. With the different families of ants the character of the colony differs very considerably. For a general account of the community life of the higher families and the general phenomena of ant life, see ANT; also DRIVER ANT; FORAGING ANT, etc.
The family Ponerithe, as pointed out by Wheeler, constitutes a primitive and generalized group of ants, wherein the colonies consist of a comparatively small number of individuals like the incipient colonies of the higher families. These small colonies appear to be annual growths formed by swarming. as in bees, and not by single fertilized female ants, unaccompanied by workers, as in the higher families, and as de scribed under ANT. Two and more colonies of the same species can be fused to form another colony without much difficulty, which is not easily accomplished with many species of the more specialized ants. Their architecture is of a primitive character, consisting of a few irregu lar and unfinished galleries. The queen and worker differ but little in size and structure. Ergatoid females, or forms intermediate between the queens and the workers, are of normal and comparatively frequent occurrence in some spe cies. The habits of the queen and worker are very similar; the female is not an individual to whom especial attention is paid by the workers. The workers show no tendency to differentiate into major and minor castes. They are carnivo rous and live by hunting, in contrast with the various harvesting, fungus-growing. honey-collect ing, and aphid-guarding members of the higher groups. They do not feed one another by regur gitation; nor are the larva fed by regur gitation, but are given pieces of insects. from which they suck the juices. It is fair to sup pose that from such generalized beginnings the highly specialized and wonderful colonies of the higher groups of ants have sprung, and that the slave-making habits, the care of honey-producing insects, the differentiation of a soldier caste. the fungus-growing habit. and others have been devel oped by gradual evolution.
The phenomenon of polymorphism (q.v.) be comes very marked with ants. although it reaches a still higher development among the termites. The causes of the modifications seen in the differ ent castes are still in dispute. Dewitz states that the caste is already determined in the insect before leaving the „; Weismann ivsociates the Caste With some hypothetical rudiments existing nt the very earliest stage of the embryonic pro cess; Herbert Spencer and others believe that the character of the insect is determined ty the nutri tion of the larva. just as is the case with the honey-bee. The chief forms of polymorphism in ants are the ordinary winged plate, the ergatoid male. the winged female, the ergatoid fertile female a form intermediate between female and worker 1, the soldier, the worker major, and one or more kind, worker minor. In addition to these
there are apparently cases of females with post metamorphie growth in the Dorylides, but these have not yet been the subject of investigation. The filet that the social insects in Which (lie pile 110111(•11a if caste or polymorphism occur, though belonging to very dillerent groups, all feed their young. is suggestive and lends weight to the theory that the differentiation is the result of character of the larval food. Emery accomits for this diffen.ntiation by assuming that it has been gradually acquired by numerous species and that we now sec it in various stages of development ; also. according to Sharp, "that the variation in nutrition does not affect all the parts of the body equally, but may be such as to carry on the development of certain portions of the organiza tion while that of other parts is arrested." The so-called intelligence of bees, and especially of ants, has been a subject of wonder and com ment on the part of many writers for hundreds of years. The ubser•ntions of Lubbock, however. indicate that bees have not the high degree of intelligence with which many writers have credited them. and that in this respect they do not compare with the higher ants, which are ranked the highest in point of intelligence among social insects. Riley, in his work entitled Social Insects front the Psychical and Erolu tumid Points of View, expressed himself as of the opinion that no one can doubt the possession by the social insects of intelligence, of conscious reasoning and reflective powers. Ile makes the statement. "We can never properly appreciate nor prillerly bring ourselves into sympathy with these lower creatures until we recognize that they are actuated by the same kind of intelligence as ours." Itethe (1s(uA), however, in discussing the question as to whether or not we may ascribe psychical qualities to ants and bees, points out the danger of the observer injecting his own per sonality into the subject investigated. lie shows, for example, that while we see, all we know at out laws and ants is that they are influenced by the light, and that it would be most unscien tific to say that they do anything as highly psychical as seeing• until it is proved. Sonic of the peculiar and apparently highly intelligent things which ants do, such as recognizing the enormous number of members of the same colony, and such as finding their way to their own nests and to food-supplies and communicating intelli gence of the location of food-supplies from one to the other, have been carefully tested by Tiethe, who concludes that he can find nothing in the phenomena exhibited by bees and ants to prove the of any psychieal qualities. Lub bock themelit that he had proved that ants com municated with one another. but Rothe used one of Luhhoek's own experiments to show that it proved nothing. lie coneludes that they learn nothing, but act mechanically in whatever they do, "their complicated reflexes being set oft by simple physiological stimuli." See facts under this head in article INSTINCT.