notum may still be recognized as very small sclerites, but in the workers of the highest and most specialized ants of the genera Formica and Camponotus the thorax appears to consist of three similar segments,

FIG. 8. Thorax of female, ergatoid and worker Ponerine ants in profile. (Emery.) A, Myrmecia pyriformis, deälated female; B, M. spadicea, ergatoid female; C, M. pyriformis, worker; msn, mesonotum; the remaining letters the same as in Figs. 6 and 7.

owing to the disappearance of the scutellum, paraptera and metanotum as separate sclerites and to the fusion of the various elements in the pleural region of each segment.

The legs of the ant show much less variation in structure than the

FIG. 9.

C

Median sagittal sections to show difference of development of thoracic segments in the worker and female Myrmica rubra. (Janet.) A, Worker; B, female; 4, posterior portion of head; b, prothorax; c, mesothorax; d, metathorax; e, epinotum (first abdominal segment); f, petiole (second abdominal segment).

thorax and are, therefore, of less taxonomic value. Each of these appendages consists of the same fixed number of joints, the coxa, trochanter, femur, tibia, and five tarsal joints. The first tarsal joint, often

FIG. 10. Strigil of Texas harvester (Pogonomyrmex molefaciens. (Original.) a, Distal end of fore tibia; b, movable, pectinated spur; c, first tarsal (metatarsal) joint.

called the metatarsus, is much elongated, especially on the middle- and hind-legs, where it functions as a kind of secondary tibia, while the terminal tarsal joint bears a pair of usually simple, but sometimes toothed, or pectinated claws. All of the tibiæ may be provided at their distal ends with spurs. These are always large and pectinated on the fore-legs, but may be simple on the middle and hind pairs. The finely and regularly pectinated spur of the fore tibia (Fig. 10, b) is of special interest on account of its beautiful structure and its function as a strigil. It is movable and curved and its concavity is opposite a similar concavity, fringed with bristles, on the base of the metatarsus. The ant draws its antennæ and posterior legs between the two opposed, pectinated surfaces and thus wipes off any adhering foreign matter.

The wings have not been used to as great an extent in descriptive works on ants as in those on other families of Hymenoptera, owing to their frequent absence in female specimens and to the permanently apterous condition of the workers, which have hitherto formed the basis of our systematic study. The venation of the fore wings, however, often exhibits important generic or even specific characters and its study, especially in fossil ants, is indispensable. It is sometimes highly variable in detail, even in males and females reared from

FIG. 11. Anterior wings of ants. (Original.) A, Ichnomyrmex cockerelli, female; B, Camponotus sansabeanus, female; C, Eciton schmitti, male; D, Strumigenys pergandei, female; E, Lasius claviger, female; F, Dolichoderus mariæ, female; G, Solenopsis molesta, female; H, Forelius maccooki, female; I, Myrmica scabrinodis, female; K, Pachycondyla harpax, male; L, Pogonomyrmex molefaciens, female; M, Tetramorium cespitum, female; N, Aphænogaster fulva, female; O, Trachymyrmex septentrionalis, female. The following are the veins of the wing: a, costal; b, subcostal; c, externomedian; d, anal; s, apterostigma; c, and g, cubital; h, discoidal and subdiscoidal; f, marginal, or radius; s, transverso-median; n, basal; m, recurrent; o, first section of radius in A, B, C, E and O, transverse cubitus in F, I and N. The following are the cells: u, first discoidal; v, costal; i, median; r, submedian; y, second discoidal; w, first cubital; w, second cubital. (These terms are used in myrmecography. Some authors, like Handlirsch, regard what is here called the "subcostal" as the radius + median, and the "subdiscoidal" as a branch of the median.)

the same mother. Several of the different types of venation which have been recognized are represented in the accompanying illustrations (Fig. 11), to which the reader is referred for the names and disposition of the various veins and cells.

The Abdomen. This region in ants is very highly specialized in all three sexual phases. In some of the most primitive tribes, like the Amblyoponii and Cerapachysii, there is no sharp separation of the segments into a pedicel and gaster; the basal, though somewhat narrower and more accentuated, preserving essentially the same structure as the more distal segments. In most ants, however, there is a welldefined pedicel which may consist of either one or two segments, very movably articulated with each other and with the thorax and gaster. In the subfamilies Dolichoderinæ and Camponotinæ the pedicel always consists of but a single segment, the petiole, which is morphologically the second abdominal segment. The same condition prevails in most Ponerinæ, except that there is a constriction behind the following or third segment, foreshadowing the development of a postpetiole. This segment is clearly separated off in all Myrmicinæ, so that in the ants of this subfamily the pedicel consists of two highly specialized, nodiform segments, and the first gastric is the fourth instead of the third abdominal segment, as in the Camponotinæ, Dolichoderinæ and Ponerinæ. In the Doryline the genera Eciton and Enictus have a distinct petiole and postpetiole in the worker, but only a single segment, the petiole, in the male and female. In Dorylus and Cheliomyrmex the base of the abdomen of the worker is more primitive and more like that of certain Ponerine ants (Amblyopone and Cerapachys).

The base of the abdomen is the seat of an interesting soundproducing, or stidulatory, organ. Landois, in a book called Thierstimmen," published in 1874, was the first to find this organ in a Ponerine ant ("Ponera quadridentata," probably Ectatomma quadridens). He believed that he had seen a similar structure in the Camponotine Lasius fuliginosus, and a few years later Lubbock (1877) figured what he took to be a stridulatory organ in L. flavus. Sharp (1893) and Janet (1893b, 1894b) have since carefully investigated these organs in several different ants. The former succeeded in finding them only in the Ponerinæ and Myrmicinæ (excepting the Cryptocerii) and believed them to be absent in the Doryline, Dolichoderinæ and Camponotina. The organ (Fig. 12) is best described as a file made of extremely fine, transverse and parallel ridges on a small area in the mid-dorsal, chitinous integument at the very base of the first gastric segment, where it is covered by the overlapping portion of the preceding segment. The edge of this segment (Fig. 12, Bp) is sharp and

turned slightly downward or inward so that it may scrape back and forth over the file (str) when the two segments are moved on each other and thereby produce a sound of very high pitch. The file is, in all probability, merely a local specialization of the fine, polygonal elevations or asperities which cover the adjacent portions of the segment and are so characteristic of the chitinous investment of many parts of the body. Each of these minute elevations is evidently secreted by one of the hypodermal chitinogenous cells. Sharp found great diversity in the structure of the stridulatory organ both among the different species and in the castes of the same species.

FIG. 12. Stridulatory organ of Myrmica levinodis. (Janet.) A, Surface view of right half of the organ; str, stridulatory surface; 1, lateral, reticulate surface; so, sense-organs; m, tendon of muscle; ap, lateral apophysis; r, radiating rugæ at base of first gastric segment. B, Median sagittal section of organ; str, stridulatory surface at extreme anterior border of first gastric segment; p, edge of postpetiole which scratches the stridulatory file str.

An interesting modification was found in an Australian Myrmicine ant of the genus Sima, which has the file divided into two parts, one consisting of coarse, the other of fine, ridges, and Sharp remarks that "a stridulatory performance by this insect might produce very extraordinary effects." Janet, in his studies of Myrmica rubra, calls attention to the fact that there are accumulations of chitinous asperities at various widely separated regions of the ant's body, especially on articulations. which might, by their movements, produce sounds. But the true stridulatory organs he finds to be situated where they were seen by