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Worker and Soldier.-Clypeus as a rule very short and not limited by sutures. Frontal carinae vertical, not covering the insertions of the antennae. Antennae inserted near the mouth and close to each other, often less than 12-jointed. Palpi at most 3-jointed, in Leptanilla HNS only one-jointed. Ocelli and eyes often absent (without exception in all African genera). Sutures of the thorax more or less vestigial; mesonotum touching the epinotom on the dorsal face, without interposed metanotum. Spurs of the tibiae pectinate or rudimentary. Postpetiole not always separated by a constriction from the third segment; however, in Eciton HNS , Aenictus HNS , and Leptanilla HNS , narrowed into the second joint of a two-jointed pedicel. Sting developed.
Female.-Permanently apterous, with the abdomen much enlarged and swollen,' very different morphologically from the worker. Clypeus as in the worker. Frontal carinae more or less separated. Antennae 10-to 12-jointed. No ocelli; eyes not more developed than in the worker; female blind when the worker is so. Segmentation of the thorax more or less rudimentary; no traces of wings or a rudiment left at the tegulae ( Dorylus HNS ). Postpetiole never separated from the third segment, the pedicel always composed of one segment. Gaster long and voluminous.
Male.-Clypeus and frontal carinae much as in the female. Mandibles developed, as a rule large; in Leptanilla HNS very short. Antennae 13-jointed; scape long, in Leptanilla HNS only slightly longer than the second joint. Eyes and ocelli well developed. Thorax with normal segmentation, winged. Postpetiole and pedicel much as in the female. Genitalia completely retractile (Dorylini and Ecitini) or exserted and not retractile (Leptanillini); subgenital lamina split or furcate; cerci absent.
larvae more or less cylindrical, with short hairs, without hooked setae; mandibles small, slender, falcate.
The three castes in this subfamily are so different from one another that their true relations remained for a very long time unsettled. The winged males were the first to be known and were originally placed with the Mutillidae. The workers and females were recognized as ants but at first classified in genera by themselves. Though their relations were more or less suspected by Lepeletier de Saint-Fargeau, Haliday, and Shuckard, the true affinities of the male and worker became only gradually known after 1850, when Savage observed for the first time in West Africa Dorylus HNS males walking in an army of Anomma HNS workers. The females, leading a permanently subterranean life, are still excessively rare in collections and known only for a few species; their capture in the smaller species is rather fortuitous, whereas in such fierce army ants as Anomma HNS it is a very troublesome operation.
G . Arnoldi gives the following general account of the habits of this subfamily:
The members of this subfamily are commonly known as driver or legionary ants. The males, which are winged and provided with eyes, are frequently taken at lights; on the other hand, the workers are blind, with the exception of some species of Eciton HNS , in which there is a pair of single-faceted eyes, and the females (excepting one species of Eciton HNS ) are both blind and wingless. The members of the genus Dorylus HNS are almost entirely subterranean in their mode of life, rarely coming to the surface except in dull, cloudy weather. The species of the subgenus Anomma HNS , which live in the more tropical and forested regions of Africa, and to which the term driver ants was originally applied, and the Ecitini of South America, are, however, usually seen above the surface, although, should the rays of the sun prove too powerful, they will construct temporarily tunnels with particles of earth held together by their saliva. The species of Aenictus HNS are not so shy of the light and may be seen foraging about even in bright sunlight. It is probable that all, or at least the majority of the species are carnivorous, although D. orientalis HNS has been shown by Green to feed also on tubers and the bark of trees.
As far as known the members of this subfamily do not as a rule make permanent nests. This course is determined by their exceedingly predatory habits, which compel the adoption of a migratory form of life together with the formation of temporary nests in localities which are sufficiently productive of animal life to detain them for any length of time. Ranging far and wide in search of prey, which consists of any animal they are strong enough to overpower, these ants must sooner or later exhaust the areas round their nests, and are forced to remove the latter to new and more productive hunting grounds.
But little is known of the habits of the Leptanillini; all species are hypogaeic. Santschi found the nest of Leptanilla nana Santschi HNS 40 cm. beneath the surface in clay soil; he caught females and workers by inundating the soil so as to force them to come out of their burrows; workers have also been taken by sifting decayed leaves. The males are attracted by lights.
A detailed account of the migrations and habits of some of the African species is given below (see under Dorylus bequaerti HNS , D. opacus HNS , D. kohli HNS , D. nigricans HNS , D. wilverthi HNS , and D. fulvus HNS ).
The Dorylinae are abundantly found in all tropical parts of the world, with the exception of the Antilles and the Malagasy Region; they are absent from the larger part of Australia. A few species reach North Africa, the coasts of Asia Minor, and the central and southern United States.
1 1915, Ann. South African Mus., XIV, p. 110.