Introduction to the Science of Sociology

by Robert Ezra Park; E. W. Burgess

The idea of society is that of a permanent co-operation in which separate living beings undertake to accomplish an identical act. These beings may find themselves brought by their conditions to a point where their co-operation forces them to group themselves in space in some definite form, but it is by no means necessary that they should be in juxtaposition for them to act together and thus to form a society. A customary reciprocation of services among more or less independent individualities is the characteristic feature of the social life, a feature that contact or remoteness does not essentially modify, nor the apparent disorder nor the regular disposition of the parties in space.

Two beings may then form what is to the eyes a single mass, and may live, not only in contact with each other, but even in a state of mutual penetration without constituting a society. It is enough in such a case that one looks at them as entirely distinct, that their activities tend to opposite or merely different ends. If their functions, instead of co-operating, diverge; if the good of one is the evil of the other, whatever the intimacy of their contact may be, no social bond unites them.

But the nature of the functions and the form of the organs are inseparable. If two beings are endowed with functions that necessarily combine, they are also endowed with organs, if not similar, at least corresponding. And these beings with like or corresponding organs are either of the same species or of very nearly the same species.

However, circumstances may be met where two beings with quite different organs and belonging even to widely remote species may be accidentally and at a single point useful to each other. A habitual relation may be established between their activities, but only on this one point, and in the time limits in which the usefulness exists. Such a case gives the occasion, if not for a society, at least for an association; that is to say, a union less necessary, less strict, less durable, may find its origin in such a meeting. In other words, beside the normal societies formed of elements specifically alike, which cannot exist without each other, there will be room for more accidental groupings, formed of elements more or less specifically unlike, which convenience unites and not necessity. We will commence with a study of the latter.

To society the most alien relations of two living beings which can be produced are those of the predator and his prey. In general, the predator is bulkier than his prey, since he overcomes him and devours him. Yet smaller ones sometimes attack larger creatures, consuming them, however, by instalments, and letting them live that they themselves may live on them as long as possible. In such a case they are forced to remain for a longer or a shorter time attached to the body of their victim, carried about by it wherever the vicissitudes of its life lead them. Such animals have received the name of parasites. Parasitism forms the line inside of which our subject begins; for if one can imagine that the parasite, instead of feeding on the animal from whom he draws his subsistence, is content to live on the remains of the other's meals, one will find himself in the presence, not yet of an actual society, but of half the conditions of a society; that is to say, a relation between two beings such that, all antagonism ceasing, one of the two is useful to the other. Such is commensalism. However, this association does not yet offer the essential element of all society, co-operation. There is co-operation when the commensal is not less useful to his host than the latter is to the commensal himself, when the two are concerned in living in a reciprocal relation and in developing their double activity in corresponding ways toward a single and an identical goal. One has given to this mode of activity the name of mutualism. Domestication is only one form of it. Parasitism, commensalism, mutualism, exist with animals among the different species.

2. Symbiosis (literally "living together")[82]

In gaining their wide and intimate acquaintance with the vegetable world the ants have also become acquainted with a large number of insects that obtain their nutriment directly from plants, either by sucking up their juices or by feeding on their foliage. To the former group belong the phytophthorous Homoptera, the plant lice, scale insects, or mealy bugs, tree-hoppers, lantern flies, and jumping plant lice; to the latter belong the caterpillars of the lycaenid butterflies, the "blues," or "azures," as they are popularly called. All of these creatures excrete liquids which are eagerly sought by the ants and constitute the whole, or, at any rate, an important part of the food of certain species. In return the Homoptera and caterpillars receive certain services from the ants, so that the relations thus established between these widely different insects may be regarded as a kind of symbiosis. These relations are most apparent in the case of the aphids, and these insects have been more often and more closely studied in Europe and America.

The consociation of the ants with the aphids is greatly facilitated by the gregarious and rather sedentary habits of the latter, especially in their younger, wingless stages, for the ants are thus enabled to obtain a large amount of food without losing time and energy in ranging far afield from their nests. Then, too, the ants may establish their nests in the immediate vicinity of the aphid droves or actually keep them in their nests or in "sheds" carefully constructed for the purpose.

Some ants obtain the honey-dew merely by licking the surface of the leaves and stems on which it has fallen, but many species have learned to stroke the aphids and induce them to void the liquid gradually so that it can be imbibed directly. A drove of plant lice, especially when it is stationed on young and succulent leaves or twigs, may produce enough honey-dew to feed a whole colony of ants for a considerable period.