Tribe 10. CATAULACII Paleotropical.-Worker and female with deep antennal scrobes on the sides of the head but formed by the true frontal carinæ only in front; further back they are bounded by special prolongations.-Male very similar to the female. Antennæ in both sexes II-jointed. Cataulacus (with the subgen. Cataulacus and Otomyrmex). Subfamily IV. DOLICHODERINÆ Forel Gizzard with a 4-sepaled, reflected calyx, completely enclosed within the crop, or without a calyx. Pedicel 1-jointed. Poison gland of worker and female without pulvinus, invaginating the cuticle of the vesicle, becoming enclosed within this organ and terminating in a knob. Tube of gland straight throughout, and furnished with lateral FIG. 85. Worker of Hemioptica scissa of Ceylon. (Bingham.) tubules for each cell. Poison vesicle variable in form, usually small, sometimes like the gland itself, highly vestigial. Sting very small (except in Aneuretus), vestigial, but not transformed into an organ to support the orifice of the vesicle. Cloacal orifice large, forming a nonciliated, transverse slit, usually ventral to the tip of the gaster. Pygidium commonly vertical or oblique antero-posteriorly and concealed under the fourth gastric segment. Antennæ 12-jointed. Anal glands almost always present and secreting an aromatic product of characteristic odor (Tapinoma odor).-Pupæ naked, never enclosed in Cocoons. Cosmopolitan. Aneuretus (Fig. 140), Dolichoderus (with subgen. Dolichoderus (Fig. 79), Hypoclinea and Monacis), Leptomyrmex, Liometopum (Fig. 80), Azteca, Semonius, Tapinoma (with the subgen. Tapinoma, Ecphorella and Doleromyrma), Turneria, Technomyrmex, Dorymyrmex, Forelius, Iridomyrmer (Fig. 86), Engramma, Bothriomyrmex, Linepithema. Subfamily V. CAMPONOTINÆ Forel Gizzard with a 4-sepaled straight, recurved or reflected calyx, which however, is always covered with circular muscles that separate it from the cavity of the crop. Pedicel 1-jointed. In the worker and female the poison gland forms a flat or oval cushion in the back of the vesicle, with a large tube but without accessory tubules for each cell. Poison vesicle large and elliptical. Sting transformed into a small vestigial apparatus which serves to support the orifice of the vesicle. All the gastric segments visible from above. Terminal segment conical, bearing at its apex the small, round, ciliated cloacal orifice. Anal glands lacking. Pupæ usually enclosed in cocoons, but sometimes naked. The following tribes are established mainly on peculiarities in the structure of the gizzard. Tribe 1. PLAGIOLEPIDII Cosmopolitan but mostly paleotropical. Plagiolepis (Fig. 87), Acropyga, Rhizomyrma, Acantholepis (with subgen. Acantholepis and Stigmacros), Brachymyrmex, Myrmelachista, Melophorus (with subgen. Melophorus and Lasiophanes), Notoncus, Aphomomyrmex, Rhopalo Ecophylla (Fig. 123), Gigantiops, Gesomyrmex (Fig. 100). Cosmopolitan. Tribe 5. FORMICII Prenolepis (with the subgen. Prenolepis, Euprenolepis and Myrmecocystus (with the subgen. Myrmecocystus and Cosmopolitan. Tribe 6. CAMPONOTII Camponotus (with the subgen. Camponotus and Colobopsis), CHAPTER IX THE GEOGRAPHICAL DISTRIBUTION OF ANTS "These craggy regions, these chaotic wilds, Their tribes, till we behold a spacious plain Their labour, covered, as a lake with waves; Thousands of cities, in the desert place Built up of life, and food, and means of life!" Few circumscribed groups of animals have a more significant geographical distribution than the ants. As colonies they are fettered to the soil or vegetation, but their winged females, though feeble flyers, may be wafted long distances by the wind and thus overcome mountain and water barriers of considerable magnitude. In these respects ants. resemble plants, which, though rooted in the ground, are able nevertheless greatly to extend the range of their species by means of windor animal-borne seeds. That ants are often carried by air currents to great distances beyond their normal range is attested by a number of facts. Annually numbers of female ants are wafted out to sea or into our great lakes to be drowned and eaten by fishes, or conveyed to desolate mountain summits where they perish in futile attempts to found colonies. Occasionally however such widely dispersed females do succeed in establishing themselves and in rearing their offspring. According to Forel (1901m) the occident ant (Pogonomyrmex occidentalis), a species peculiar to the Great Plains, has been taken in Hawaii, and King (1901a) has found in Massachusetts a single colony of Formica neoclara, an ant restricted, so far as known, to the mountain valleys of Colorado. This method of dispersal is, of course, denied to all ants like the Dorylinæ, certain Ponerinæ and Myrmicinæ, whose females are wingless, since these insects cannot cross bodies of water nor high mountain ranges. But as the Doryline are migratory ants, and, as a rule, do not inhabit permanent nests, their colonies compensate, to a certain extent, for the apterous condition of their females. There is, however, a passive displacement or dissemination of whole colonies in certain. species like the fire-ant (Solenopsis geminata), which often nests in low-lands subject to frequent and sudden inundations. Von Ihering (1894) has made the interesting discovery that when a nest of these ants is flooded, they agglomerate to form a ball 16-25 cm. in diameter, which encloses the brood in the center. This ball is borne along on the surface of the water while its living units keep shifting their position to avoid too prolonged immersion, till the shore or some projecting rock or tree-trunk is reached, when the colony scrambles out of the uncongenial element. I am informed by a gentleman from Louisiana that this same ant resorts to the same method of saving its colonies in the flooded bayous of the Southern States. Similar observations have been made by Savage (1847) on the African driver ants (Anomma arcens) and by Ern. André (1885) on European ants. Finally, ant colonies or fertile female ants are often transported by man from land to land as stowaways in the cargoes of ships and railway trains. Every botanical garden annually receives several species of these insects from the tropics in the pseudobulbs of orchids, among the leaves of aroids or tillandsias, or in the soil and moss adhering to the roots of plants, and some of the smaller species thus unintentionally imported manage to establish themselves permanently in the hot-houses. Owing to these various means of dissemination, the species of ants have become more widely distributed than any other insects, with the possible exception of the Diptera. Some of our American forms, for example, Dorymyrmex pyramicus, range from Illinois to Argentina. Many species, like Eciton cæcum and Solenopsis geminata, are coëxtensive with the tropical and subtropical portions of America, and the latter also occurs in the tropics of the Old World. The former, being a Doryline ant, does not occur in the West Indies. Still other species, like Camponotus herculeanus, Formica fusca and sanguinea, extend over the whole north temperate portion of the globe, and C. maculatus is represented by subspecies or varieties on every continent and on many of the outlying islands. The distribution of ants may be studied either from a faunistic or from an ethological point of view. In faunistic studies the emphasis. is placed on the areas or ranges covered by the various species, subspecies and varieties and on the bearing of such distribution on the genesis or descent of taxonomic groups as units. And since the existing fauna is unquestionably derived from previous faunas, which must have determined its character and composition, we are compelled to |