Details of the modes in which the great communities of the leaf-cutting Attidae are maintained, are still wanting. The females do not, we have been informed by Mr. Hart, possess any considerable powers of aftergrowth, so that there is no reason to suppose them to be unusually prolific. At certain seasons great swarms of winged individuals are produced, and after leaving the nests pair in the manner of our European Myrmica. Possibly the females may, after losing their wings, again enter the large communities. Von Ihering states that the workers of Atta lundi are fertile.
iii. The group Pseudomyrmini includes the genera Pseudomyrma and Sima, which are by some entomologists treated as but a single genus. The antennae are inserted near together on the front of the head; there is no carina on the head external to their insertion, and the clypeus does not extend forwards between them. The Insects are usually of elongate form, possess a sting, and have a naked pupa. The group occurs in both hemispheres, but is exclusively exotic, and but little is known of the habits of its members. Forel has recently observed that numerous species live inside dried stems of grass or in hollow twigs, and are beautifully adapted for this mode of life by their elongate form, some of them being as slender as needles. Some interesting observations have been made in Nicaragua by Belt on Pseudomyrma bicolor and its relations with an acacia-tree, in the thorns of which it lives. The acacia in question is called the bull's-horn thorn, because the branches and trunk are armed with strong curved spines, set in pairs, and much resembling the horns of the quadruped whose name they bear. The ant takes possession of a thorn by boring a small hole near the distal extremity, and forms its nest inside. The leaves of this plant are provided with glands that secrete a honey-like fluid, which it appears forms the chief, if not the sole, subsistence of the ant. Belt considers that the presence of the ant is beneficial to the acacia; he supposes that the ants assume the rights of proprietors, and will not allow caterpillars or leaf-cutting ants to meddle with their property; the leaves are, he thinks, so preserved to the benefit of the tree.
Fig. 72—Sima rufo-nigra and its associates. A, winged female; B, worker, of the ant; C, Rhinopsis ruficornis; a fossorial wasp of the sub-family Ampulicides; D, a spider, Salticus sp. The coloration is extremely similar in all these creatures.
Rothney has given some particulars of the habits of Sima rufo-nigra, an ant of this group that appears to be not uncommon near Calcutta, where it lives on the trunks of trees in company with a spider and a wasp that greatly resemble it in form and in colour. The three creatures seem to associate together on amicable terms; indeed the wasp and the ant occasionally indulge in wrestling matches without doing one another any serious harm. In connection with this fact we may observe that other species of ants have been observed to indulge in sports and feats of agility.
S. leviceps, an Australian species of this genus, is furnished with a stridulating file that has the appearance of being constructed so as to produce two very different kinds of sounds.
Fig. 73—Stridulating file of Sima leviceps.
iv. The Cryptocerini are distinguished from other ants by their antennae being inserted at the sides of the head, where they are placed between ridges or in a groove into which they can be withdrawn; when in some cases they are entirely concealed. These ants assume a great variety of shapes and forms, some of which look almost as if they were the results of an extravagant imagination. The skeleton is usually much harder than it is in other ants; the abdomen consists almost entirely of one very large segment, there being, however, three others visible at its extremity; these segments can be only slightly protruded, and the ants have no power of stinging. They are probably most of them arboreal in their habits. Nearly all of the known forms are exotic. According to the observations of Bates the species of the genus Cryptocerus in the Amazons Valley may frequently be observed in dry open places on low trees and bushes, or running on branches of newly felled trees; they also visit flowers abundantly. The species generally are wood-borers, usually perforating the dead branches of trees. C. atratus has been observed to construct its nests in the dead, suspended branches of woody climbers; a number of neatly drilled holes are all that can be seen externally; but, inside, the wood is freely perforated with intercommunicating galleries. Each community appears to consist of a single female and two kinds of workers; the latter in some species are quite unlike each other, differing in the form of the head, and in the armature of the thorax and nodes of the peduncle. The species of Cryptocerus appear to be omnivorous, and are frequently attracted by the excrement of birds. The pupae are not enclosed in a cocoon. In the South of Europe two very minute ants, of the genera Strumigenys and Epitritus, belonging to this family, are met with under very large stones partly embedded in the earth. They are of the greatest rarity.
