Ant colonies > Ant body parts > Ant integument

Ant integument

The chitinous investment, or integument varies greatly in thickness in the different species of ants, being very hard and brittle in many of the more primitive groups (Ponerinae, Myrmicinae, Dolichoderus, Polyrhachis) and thinner and more pliable in the more recently developed forms (most Dolichoderinae and Camponotinae).

The microscopic character of the integument is of considerable importance to the taxonomist, especially in the more delicate discrimination of geographical subspecies and varieties and may be considered under the captions of sculpture, pilosity, pubescence and color.

These all present a bewildering variety of modifications. In some ants the surface of the body is very glabrous and shining, in others opaque, punctate, foveolate, rugulose, rugose, tuberculate, striate or reticulate, and these sculptural characters may be combined in the most diverse patterns. The term pilosity applies to the longer, reclinate, erect or suberect hairs, the term pubescence to the minute, appressed tomentum, which may cover the whole or portions of the body and appendages. Both the hairs and pubescence vary greatly in length and density or abundance, and the former may be tapering and pointed, straight, flexuous, or hooked, obtuse or clavate, or dilated and flattened to form scales.

No doubt all of these differentiations in sculpture, pilosity and pubescence are correlated with the delicate tactile sense of the ants. Certainly one who has examined many species of ants will have no difficulty in understanding why these blind or nearly blind insects seem to display such keen delight in palpating with their antennae and burnishing with their tongues the exquisitely chased or chiselled armor of their fellows.

In some ants the hairs may be specialized for particular functions on certain portions of the body. We find this to be the case, for example, in several genera of desert ants which have the hairs on the lower surface of the head greatly elongated and directed forward (Pogonomyrmex, Ocymyrmex, Cratomyrmex, Messor, Goniomma, Oxyopomyrmex, Holcomyrmex), or arranged in a tuft on the lower lip (Myrmecocystus, Melophorus). These hairs, which I have called gular and mental ammochaetae, are employed by the ants in removing the dust and sand from the strigils or combs on the fore­legs (vide infra). In deserts these insects easily become covered with the dry soil or sand and have to remove it from their bodies and limbs by means of the strigils. These organs are then thrust along the ammochaetae in much the same way as we clean a comb by means of threads. The clypeus and mandibles of many ants are also fringed with unusually long hairs (clypeal and mandibular ammochaetae) which are employed in removing the dust, etc., from the surfaces of the fore-legs.

The colors of ants are, as a rule, testaceous, yellow, brown, red, or black, but a few genera (Rhytidoponera, Calomyrmex, Macromischa, Iridomyrmex) and a few North American species of Pheidole (metallescens and splendidula) have metallic colors.

The non-metallic tints are often highly variable, even within the limits of single species. Color patterns are rarely developed and are usually found only on the tipper surface of the gaster, a region which often differs in color from the head and thorax.

The appendages, -as in other insects, are apt to be paler than the trunk. The coloration of the hairs and pubescence, like that of the surface, may be extremely variable in the same species. To the integument belong also a number of glands, but these will be described in connection with the glands of the internal organs.