FIG. 51. Colony of Acanthomyops claviger, showing workers, deälated and virgin females, males, worker, male and female cocoons, X 2.

Hubbard and Dr. O. S. Strong).

(Photograph by J. G.

ANTS.

many other insects, which made its appearance among the solitary species, like the Tenthredinidæ and Cynipidæ, long before the development of social life. Moreover, polymorphism may occur in male insects which, of course, are not parthenogenetic. That parthenogenesis is intimately connected with sexual dimorphism, at least among the

FIG. 52. Pheidole instabilis. (Original.) a, Soldier: b-e, intermediate workers; f, typical worker (micrergate); g, deälated female; h, male.

social Hymenoptera, seems to be evident from the fact that the males usually if not always develop from unfertilized, the females from fertilized eggs.

While the bumble-bees and wasps show us the ancient stages in the development of polymorphism, the ants as a group, with the exception of a few parasitic genera that have secondarily lost this character, are all completely polymorphic. It is conceivable that the

FIG. 53. Cryptocerus varians. (Original.) a, Soldier; b, same in profile; c, head of same from above; d, worker; e. female; f, male.

development of different castes in the female may have arisen independently in each of the three groups of the social Hymenoptera, although it is equally probable that they may have inherited a tendency to polymorphism from a common extinct ancestry. On either hypothesis, however, we must admit that the ants have carried the development of the female castes much further than the social bees and wasps,

since they have not only produced a wingless form of the worker, in addition to the winged female, or queen, but in many cases also two distinct castes of workers known as the worker proper and the soldier. Different authors have framed very different conceptions of the phylogenetic beginnings of social life among the Hymenoptera and consequently also of the phylogenetic origin and development of polymorphism. Thus Herbert Spencer (1893) evidently conceived the colony as having arisen from consociation of adult individuals, and although he unfortunately selected a parasitic ant, the amazon (Polyergus rufescens), on which to hang his hypothesis, there are a few facts which at first sight seem to make his view applicable to other social Hymenoptera. Fabre (1894) once found some hundreds of specimens of a solitary wasp (Ammophila hirsuta) huddled together under a stone on the summit of Mt. Ventoux in the Provence, at an altitude of about 5,500 feet, and Forel (1874) found more than fifty deälated females of Formica rufa under similar conditions on the Simplon. I have myself seen collections of a large red and yellow Amblyteles under stones on Pike's Peak at an altitude of more than 13,000 feet, and a mass of about seventy deälated females of Formica gnava apparently hibernating after the nuptial flight under a stone. near Austin, Texas. I am convinced, however, that such congregations are either entirely fortuitous, especially where the insects of one species are very abundant and there are few available stones, or, that they are, as in the case of F. rufa and gnava, merely a manifestation of highly developed social proclivities and not of such proclivities in process of development.

A very different view from that of Spencer is adopted by most authors, who regard the insect colony as having arisen, not from a chance. concourse of adult individuals, but from a natural affiliation of mother and offspring. This view, which has been elaborated by Marshall (1889) among others, presents many advantages over that of Spencer, not the least of which is its agreement with what actually occurs in the founding of the existing colonies of wasps, bumble-bees and ants. These colonies pass through an ontogenetic stage which has all the appearance of repeating the conditions under which colonial life first made its appearance in the phylogenetic history of the species-the solitary mother insect rearing and affiliating her offspring under conditions which would seem to arise naturally from the breeding habits of the nonsocial Hymenoptera. The exceptional methods of colony formation seen in the swarming of the honey bee and in the temporary and permanent parasitism of certain ants, are too obviously secondary and of too recent a development to require extended comment. The

bond which held mother and daughters together as a community was from the first no other than that which binds human societies together the bond of hunger and affection. The daughter insects in the primitive colony became dependent organisms as a result of two factors inadequate nourishment and the ability to pupate very prematurely. But this very ability seems to have entailed an incompleteness of adult structure and instincts, which in turn must have confirmed the division of labor and thus tended to perfect the social organization.

Before further discussing the problems suggested by this view of the origin of the colony and the general subject of polymorphism, it will be advisable to pass in review the series of different phases known to occur among ants. This review will be facilitated by consulting the accompanying diagram, in which I have endeavored to arrange

the various phases so as to bring out their morphological relations to one another. The phases may be divided into two main groups, the normal and the pathological. In the diagram the names of the latter are printed in italics. The normal phases may be again divided into primary or typical, and secondary or atypical, the former comprising only the three original phases, male, female and worker, the latter the remaining phases, which, however, are far from having the