Page:The New International Encyclopædia 1st ed. v. 10.djvu/747

* INSECT. 659 INSECT. more especially the larvs of certain silk-spinning moths, like the European processionary moth (Cnctkocatnpa processionea), and less marked- ly the American tent caterpillar and fall v.cbworm (qq.v.). These tents or webs for community feeding are carried to a higher de- gree of perfection in the European tineino moths of the genus Hyponomeuta, and still more perfectly in the community nests of a tropical butterfly (Eiicheira sociulis). A number of moths make communal cocoons, but nearly all of these are tropical. The beginning of a true communal life is seen with the ambrosia beetles (q.v. ) of the family Scolytid.-p. These are beetles which make galleries under the bark of trees, apparently cultivating a fungus which they use as food, preparing a bed for its cultivation ; they also carefully remove excrement from the fungus gardens and practically bury their dead. The most perfect socialism, however, occurs among the bees, wasps, and ants of the order Hymenop- tera, and among the termites or so-called 'white ants' of the order Isoptera. Not all bees are social. A large group is composed of solitary bees. Among the social bees a more or less primi- tive social life is found with the bumblebees. Here there is a communal existence. Xesls are made, cells are constructed for the young, the young are fed by the adults, and there is a sepa- ration into three castes, viz. females, males, and drones. There is also the beginning of .a separa- tion of the drones into two castes, the larger ones in general attending to the mending of tlic cover- intj of the nests and to the ripening of the honey, while the smaller ones for the most part do the inside housework, such as the wax-repairing and the nursing of the young. The community life of the hive or honey bee is much more compli- cated than that of the bumblebee, but the work- ers seem to be more uniform in their duties. The stingless tropical bees of the genera Trigona and Melipona form very large communities, some of them even exceeding in size those of the honey- bee, but the social life is practically the same. See Bee. The wasps are also both social and solitary. The social species belong for the most part to the genera Vespa and Polistes. Their communities are much like those of the social bees. They are, however, not so perfect and not so persistent as those of the true honey-bee or the ants, but re- semble more nearly those of the bumblebee. The comnumities of the bumblebees and the wasps are annual. Those of the honey-bee and the ants, as well as of the termites, last for a number of years. Among the wasps is a form known a.s worker, just as with the social bees, and the workers here, as in the other cases, are undcvel- o]ied females. Here also, as with the social bees, these undeveloped females or workers may lay eggs which invariably produce males or drones. Most of the social wasps make paper cells and nests, using for this purpose a wood-pulp com- posed of fragments of wood moistened with saliva, and macerated in the mouth. The economy of the social wasps is not perfectly understood, doubtless owing to the difliculty of studying them, due to the irritability of the insects and to their poisonous stinffin?. The size of the communities varies at the season when they are largest, from a few individuals to many hundreds, as mr.ny as 1200 cells being found in a single nest. On the approach of winter the males and workers perish and the fertile females crawl into such protected situations as crevices of walls and in the bark of trees, and there pass the winter in the dor- mant state. At the opening of spring each sur- viving female founds a new colony. At first she performs the duties of both queen and worker. A small nest is made, eggs are laid in it, and when the larva; hatch they are fed and cared for by the queen until they are mature. This first generation is composed entirely of workers. They relieve the queen of the duties which belong to them, and from this time forth her onlj' duty i» to lay eggs. The workers are engaged in the enlargement of the nest, in the construction of new cells, and in the care of the young. With the ants we come 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 AxT; also Driver Axt; Foraginq Ant, etc. The family Ponerida^. 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 difliculty, 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 hom especial attention is paid by the workers. The workers show no tendency to ditTerentiate 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 larvje fed bj- regxir- 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 difTer- ent castes are still in dispute. Dewitz states that