orous habit, for a carnivorous ant, used to collecting insects and crushing their hard integuments with its powerful mandibles, is already fully equipped with the apparatus necessary for dealing with seeds. And although many harvesting ants have more convex mandibles and blunter teeth than carnivorous species, it is impossible merely from examination of the mouthparts to ascertain whether an ant is granivorous or not. It may be doubted, furthermore, whether there is such a thing as a purely granivorous ant. There is clearly no advantage in an ant's losing its taste for the succulent tissues of other insects, although there is an obvious advantage in its supplementing this diet with seeds during certain seasons of the year. Indeed, many, if not all, of the species mentioned in the following pages are quite as eager to secure insect food as seeds, especially while they are raising their brood, and unquestionably many ants that are supposed to be exclusively predaceous will, on closer study, be found to be more or less granivorous.

FIG. 150.

Worker of the Indian harvester, Holcomyrmex scabriceps. (Bingham.)

If the foregoing considerations are correct, we should expect to find the harvesting ants arising sporadically and often in distantly related genera and species. This appears to be the case, for although these insects belong to a single subfamily, the Myrmicinæ, they occur in at least three of the tribes, the Solenopsidii, the Tetramorii and the Myrmicii. Among the Solenopsidii, however, only a single species of Solenopsis (S. geminata) is known to be granivorous, and only a portion of the enormous genus Pheidole comprises such species. The small genus Pheidologeton is also granivorous. Among the Tetramorii, Tetramorium cespitum is only rarely and sporadically granivorous, and this is perhaps true of a certain number of species of Meranoplus. Among the Myrmicii, Messor and Ischnomyrmer comprise harvesting species, whereas the species of the allied Stenamma and Aphanogaster are predaceous. Holcomyrmex, now regarded as a subgenus of Monomorium, Pogonomyrmex, Oxyopomyrmex (with its subgenus Goniomma), which are closely related to Messor, and probably also Ocymyrmex, are highly granivorous.

The earliest of all recorded myrmecological observations undoubtedly relate to two harvesting ants, Messor barbarus and structor. The former occurs throughout the Mediterranean littoral of Europe, Asia

L

and Africa and presents in the warmer portions of its range, which is now known to extend southward to the Cape of Good Hope, a bewildering complex of subspecies and varieties. M. structor.seems to be absent in Africa, but ranges through southern Europe and Asia as far as Java. The ancient peoples were undoubtedly familiar with the granivorous habits of these ants and probably also with those of a third species, M. arenarius, inhabiting the deserts of North Africa. To them refer the many allusions in the writings of Solomon and the Mischna, and of the classic writers Hesiod, Esop, Elian, Plutarch, Orus Apollo, Plautus, Horace, Virgil, Ovid and Pliny. Mediæval authors, like Aldrovandus and Bacon, merely repeated the accounts of the ancients. The entomologists of the early portion of the last century, however, failing to find any harvesters among the ants of temperate Europe, began to doubt, or even to deny their existence. This skepticism is much in evidence in the works of Gould (1747), Latreille (1802), Huber (1810), Gené (1845), Kirby and Spence (1846), and Blanchard (1871). The subject was taken up, however, by Sykes (1829) and Jerdon (1851) in India, by Moggridge (1873) in southern France and by Buckley (1861a), Lincecum (1862), McCook (1877a, 1879c), Morris (1880) and Mrs. Treat (1878) in the United States. These authors succeeded in showing that the ancient accounts were correct. For a detailed history of the subject and for extracts from the various authors of antiquity, the reader is referred to Bochart's "Hierozoicon" and to the works of Moggridge and McCook. Here I shall confine myself to the recent observations, considering first, in all brevity, the Old World harvesters and concluding with a somewhat fuller account of our American species.

FIG. 151.

text.

Sykes was the first of modern observers to describe the storing of seeds by ants. He saw Pheidole providens at Poona, India, bringing grass seeds, which had been moistened by the rains, out of the nests and exposing them to the sun to dry. Jerdon confirmed these observations on Ph. providens, Ph. diffusa and Solenopsis rufa, a subspecies of the tropicopolitan S. geminata. He saw the ants not only drying their piles of seeds but also collecting them from different plants and storing

them in the nests, although he was unable to ascertain the purpose of these activities. All doubt was removed, however, by Moggridge's excellent work, which was carried out at Mentone in 1871 and 1872 on Messor barbarus and structor, the very species that had been observed by the ancients. He opened the nests of these ants and studied their granaries, which are flat chambers connected by galleries and irregularly scattered over an area sometimes nearly 2 m. in diameter and to a depth of about 35 cm. in the soil. He saw the workers collect the seeds from the ground or even pluck them from the plants, remove

FIG. 152. Nest of Messor pergandei in Arizona desert, in a spot where the alkali prevents the growth of nearly all plants except Suada. The dark material at the border of the crater is seeds and chaff rejected by the ants. In more favorable spots in the desert the seeds produce the ring of plants seen in Fig. 154. (Original.)

their envelopes and cast the chaff and empty capsules on the kitchen middens outside the nest. During the winter a nest of the average size may contain as much as a quarter of a liter of seeds. Among the stores in the granaries he was able to recognize seeds belonging to at least eighteen different families of plants. In confirmation of Pliny and Plutarch he maintains that the ants bite off the radicle to prevent the seeds from germinating, a process which is also arrested by bring

ing them when damp with the rain to the surface, spreading them in the sun and then carrying them back to the granaries. Some of the seeds sprout, nevertheless, either in the nests or on the kitchen middens. "As the ants often travel some distance from their nest in search of food, they may certainly be said to be, in a limited sense, agents in the

(Original.)

dispersal of seeds, for they not unfrequently drop seeds by the way, which they fail to find again, and also among the refuse matter which forms the kitchen midden in front of their entrances, a few sound seeds are often present, and these in many instances grow up and form a little colony of strange plants. This presence of seedlings foreign to the wild grounds in which the nest is usually placed, is quite a feature where there are old established colonies of Atta barbara, where young plants of fumitory, chickweed, cranesbill, Arabis Thaleana, etc., may be seen on or near the rubbish heap. . . . One can imagine cases in which the ants during the lapse of long periods of time might pass the seeds of plants from colony to colony, until after a journey of many stages, the descendants of the ant-borne seedlings might find them

selves transported to places far removed from the original home of their immediate ancestors." Moggridge also observed that not only Pheidole pallidula but also Ph. megacephala, an Old World ant which now overruns the warm portions of both hemispheres, are harvesting ants.

The more recent investigations of Forel (1894a), Ern. André (1881e), Emery (1899a), Lameere (1902), Escherich (1906), and others have confirmed Moggridge's observations. Forel and Lameere have studied the habits of M. barbarus and arenarius in the deserts of North Africa. According to Forel, the latter species, which is the most powerful insect of that region, excavates enormous nests over an area 7-10 m. in diameter and to a depth of 2 m., with several openings,

FIG. 154. Crater of Messor pergandei in the Arizona desert, showing ring of herbaceous plants that have sprung up from discarded seeds in the chaff circle. (See Figs. 152 and 153.) (Original.)

each surmounted by a crescentic crater sometimes 50 cm. broad and made of coarse sand pellets. The granaries are flat chambers about 15 cm. in diameter and 1.5 cm. high, connected by galleries with one another and with the surface. Lameere believes that the area occupied by single colonies of this ant is even greater than that given by Forel. He also describes the harvesting habits of another Messor (M. caviceps)