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Article XXIII.—THREE NEW GENERA OF MYRMICINE ANTS FROM TROPICAL AMERICA.1
By William Morton Wheeler.
In a collection of neotropical ants comprising several hundred specimens, loaned me for study by the authorities of the United States National Museum, I find the three following species, each of which represents a genus hitherto undescribed.
Nesomyrmex gen. nov.
Female. Allied to Leptothorax. Body small, slender. Head longer than broad, convex above in the middle, flattened below, broader behind than in front, and strongly impressed in the region of the eyes, which are rather large and in front of the middle. Mandibles moderately convex, dentate. Clypeus small, feebly convex, with rounded and projecting anterior border. Frontal area elongate-triangular, rather indistinct; frontal carinae short but well-developed, frontal groove absent. Antennae 11-jointed, funiculus with a 3-jointed club. Thorax long and narrow, flattened above and on the sides, with acute and prominent humeri. Mesonotum subtriangular, narrowed to a rounded point anteriorly. Epinotum dentate; epi-sternal angles rounded. Petiole not pedunculate, with an anterov entrai tooth and well developed dorsal node. Postpetiole depressed, constricted behind. Gaster short, elliptical, flattened above, more convex beneath, the first segment very large; sting well developed. Legs stout; femora clavate, incrassated; middle and hind tibiae without spurs. Wings long, minutely hairy, with large apterostigma, one cubital cell, a small closed radial and no discal cell. Hairs on body short, sparse, erect and clavate; pubescence closely appressed.
Nesomyrmex clavipilis sp. nov.
(Fig. 1.)
Female. Length 2.8 mm.
Head with feebly and broadly excised, marginate posterior border; posterior corners and cheeks rounded. Mandibles 4-toothed. Antennal scape reaching to about half the distance between the eye and the posterior corner of the head. Funiculus much longer than the scape; its first joint as long as the 3 succeeding joints together; joints 2-7 broader than long; joints 8 and 9 subequal, together decidedly shorter than the terminal joint. Thorax somewhat narrower than the head, narrower behind than in front, with steep sides. Epinotum in profile with short, stout, blunt teeth and subequal base and declivity, the former feebly convex, the latter
1 Contributions from the Entomological Laboratory of the Bussey Institution, Harvard University, No. 23.
259
260 Bulletin American Museum of Natural History. [Vol. XXVIII,
flattened. Petiole longer than broad, broadest in the middle; in profile with a moderately high node in the middle, its upper surface depressed, its anterior and posterior declivities subequal and slightly concave. Postpetiole from above transversely elliptical, twice as broad as long and one-third again as broad as the petiole; in profile convex above in front, flattened behind, below with a prominent transverse welt. Gaster considerably larger than the head, its anterior border slightly angular on the sides.
Body, including the mandibles, very finely and densely punctate, opaque; legs and upper surface of gaster somewhat shining and more sparsely punctate.
Fig. 1. Nesomyrmex clavipilis sp. nov.; a, female in profile; 6, head; c, thorax of same seen from above.
Clypeus and front feebly, longitudinally rugose; remainder of head above indistinctly reticulate-rugulose.
Hairs and pubescence yellowish, the former sparse and clavate on the clypeus, upper surface of the head, thorax, pedicel and tip and lower surface of the gaster, longest on the venter and posterior borders of the gastric segments. Pubescence of scapes, cheeks and legs short, on the upper surface of the first gastric segment longer and coarser.
Color yellowish brown; mandibular teeth, eyes and a spot at the inner border of each ocellus, black. Head with a brown impressed spot about the size and shape of the eye on each side between the eye and the lateral ocellus. Wings yellowish gray, with dilute yellow veins and pale brown apterostigma.
Described from a single specimen (No. 13197, U. S. Nat. Mus. Coll.) taken by Mr. H. H. Smith at Balthazar on the windward side of the Island of Grenada, W. I.
1910.] Wheeler, Three New Genera of Myrmicine Ants. 261
The genus Nesomyrmex, so far as it is possible to judge from this female specimen, is closely related to Leptothorax. It differs, however, in venation, especially in lacking the discal cell, and in the structure of the head and thorax.
Apsychomyrmex gen. nov.
Worker. Small species allied to Rogeria Emery. Head rather large; mandibles moderately convex, dentate. Clypeus very short, much depressed on the sides, elevated in the middle to form a narrow, bidentate plate, which is fused with the frontal carinae. These are well developed, rather closely approximated and projecting upward and slightly outward, and include an elongate, impressed frontal area which runs forward as a narrow groove to the tip of the clypeal plate: Antennal fossae large, continued backward and outward over the sides of the clypeus. Eyes small, consisting of a few ommatidia, placed a little in front of the sides of the head. Ocelli absent. Antennae stout, 12-jointed, funiculus ending in a 2-jointed club, the last joint of which is very large and glandiform; joints 2-8 transverse, much broader than long. Thorax scarcely longer than the head, including the mandibles, narrower than the head, with rounded humeri and inferior pronotal angles; without promesonotal and mesoëpinotal sutures; pro- and mesonotum convex and rounded above; epinotum narrowed and more depressed, dentate; episternal angles short, rather acute. Petiole pedunculate, without an anteroventral tooth; node well-developed. Postpetiole short, very convex above, constricted behind. Gaster larger than the head, oval; first segment large, convex dorsally; sting apparently very small or vestigial. Legs rather stout; femora feebly clavate; middle and hind tibiae without spurs. Body, excepting the gaster and appendages, coarsely sculptured. Hairs long and simple.
Apsychomyrmex myops sp. nov.
(Fig. 2.)
Worker. Length 2.3 mm.
Head distinctly longer than broad, subelliptical, with feebly convex posterior •and evenly rounded anterior borders, as broad in front as behind., Mandibles with oblique masticatory borders, bearing 2 stout apical and 2 or 3 smaller basal teeth. Antennal scapes reaching about half way between the eyes and the posterior corners of the head; first funicular joint nearly as long as the two succeeding joints taken together; joints 2-8 subequal; joint 9 somewhat longer; joint 10 twice as long as joint 9; distinctly broader and separated off from it as the base of the 2-jointed club; terminal joint more than $ as long as the remainder of the funiculus. Epinotum with subequal base and declivity, the former horizontal, the latter straight and sloping; teeth short, acute, directed upward, outward and backward. Petiole with a high, rounded node, which has a long concave anterior and shorter, more abrupt, convex posterior slope; seen from above the node is about as broad as long. Postpetiole from above circular, a little broader than the petiole, very convex above, with an acute, transverse welt on its very short ventral side.
Mandibles somewhat shining, coarsely and sparsely punctate. Head, thorax, petiole and postpetiole subopaque, coarsely reticulate-rugose, cheeks and pleurae
262 Bulletin American Museum of Natural History. [Vol. XXVIII,
indistinctly longitudinally rugose; lower surface of petiole, and posterior declivity of the petiole and postpetiole transversely rugose. Frontal area smooth and shining ; epinotal declivity and gaster shining, the former rugulose, the latter very finely and indistinctly punctate. Antennal scapes and legs shining and sparsely punctate.
Fig. 2. Apsychomyrmex myops sp. nov.; a, worker in profile; b, head of same from above; c, antenna.
Hairs yellowish, very long and flexuous; erect or suberect on the body and mandibles, appressed on the legs and scapes.
Body black, with deep red articulations; mandibles, legs and antennae ferruginous; scapes and middle portions of the femora and tibiae blackish.
Described from a single specimen (No. 13198, U. S. Nat. Mus. Coll.) taken by Messrs. Schwarz and Barber at Livingston, Gautemala.
The genus Apsychomyrmex is, in many respects, rather closely related to Rogeria, especially in general habitus, the shape of the head, thorax and petiole and in having small eyes and 12-jointed antennae, but it differs in the shape of the clypeus, with the bidentate median plate fused with the frontal carinae, in the size and prominence of these carinas, the extent of the antennal fossae, in having 2-jointed instead of 3-jointed antennal clubs, in the spurless middle and hind tibiae and the much coarser sculpture. It is probable that the Myrmica blanda described by F. Smith from Brazil belongs to Apsychomyrmex rather than to Rogeria. Smith describes the antennae of this ant as having 3-jointed clubs, and as will be seen from the accompanying figure (Fig. 2c) the composition of the club in Apsychomyrmex may be open to this
1910.] Wheeler, Three New Genera of Myrmicine Ants. 263
interpretation. There is, however, a somewhat more marked constriction between the antepenultimate and penultimate joints than between the former and the remainder of the funiculus in the species here described.
Lachncmyrmex gen. nov.
Worker. Small and monomorphic. Head nearly as broad as long, broader behind than in front, convex above. Mandibles dentate at/the apex. Ocelli absent. Eyes rather small, convex, consisting of large ommatidia, situated in front of the middle of the head and below a deep scrobe, which is confluent anteriorly with the antennal fovea and is large enough to enclose the whole antennal scape. Frontal carinae broad, square in front, projecting laterally on each side over the anterior portion of the scrobe and continued back as its sharp mesial border. Frontal area and groove obsolete. Clypeus narrow, convex, with rounded, projecting anterior border. Antennae 12-jointed; funiculus with a distinct 2-jointed club and joints 2-9 very short. Thorax narrower and somewhat longer than the head including the mandibles, narrower behind than in front; pro- and mesonotum rounded and convex above, not separated by a suture; inferior pronotal angles rounded; meso-ëpinotal constriction pronounced; epinotum depressed, armed with long spines; metasternal angles prolonged into sharp teeth. Petiole and postpetiole small, with very low nodes; petiole pedunculate, without an anteroventral tooth. Gaster about the size of the head, globose, without anterior angles; first segment very large and convex; sting small and slender. Legs rather stout, femora and tibiae feebly clav-ate, middle and hind tibiae without spurs. Head, thorax, petiole and postpetiole roughly sculptured. Body and appendages covered with moderately abundant, very long, simple and flexuous hairs.
Female (deâlated). But little larger than the worker and of a very similar conformation. Eyes and ocelli rather small. Thorax short and stout, but little longer than broad, nearly as high as long and nearly as broad as the head. Mesonotum and scutellum convex; epinotum like that of the worker.
Lachnomyrmex scrobiculatus sp. nov.
(Fig. 3.)
Worker. Length 2-2.3 mm.
Head with rounded posterior border and corners and nearly straight sides slightly converging anteriorly. Mandibles moderately convex, with two apical teeth and the remainder of the masticatory border sharp and edentate. Clypeus with a few widely separated longitudinal ridges. Antennal scapes slightly incrassated distally, as long as the scrobes; first funicular joint as long as broad; joints 2-9 increasing very gradually in length towards the club but always remaining much broader than long; basal about i as long as the terminal joint of the club. Pro-and mesonotum forming a hemispherical mass, nearly circular when seen from above; epinotum somewhat longer than broad, with subparallel sides; base horizontal, shorter than the concave, very sloping declivity; spines slender, straight and acute, directed upward, backward and slightly outward, longer than their distance apart
264 Bulletin American Museum of Natural History. [Vol. XXVIII,
at the base and with their extreme tips slightly bent forward. The acute episternal angles are directed upward and their tips are also very feebly recurved in some specimens. Petiole narrow in profile, with a low, rather acute node, with concave anterior and posterior declivities; seen from above the upper border of the node is transverse and the whole segment is but little broader behind than in the region of the peduncle. Postpetiole only J again as broad as the petiole; from above a little broader than long, subrectangular; in profile its upper surface is evenly and feebly rounded, the lower surface short, with a prominent transverse welt anteriorly.
Mandibles smooth and shining, sparsely and inconspicuously punctate. Head, thorax, petiole and postpetiole subopaque, coarsely reticulate-rugose, the rugae on the upper surface of the head longitudinal, less coarse and much more irregular on the thorax, petiole and postpetiole. Antennal scrobes and epinotal declivity shin-
Fig. 3. Lachnomyrmex scrobiculatus sp. nov.; a, worker in profile; 6, head of same from above; c, antenna.
ing, transversely rugulose. Gaster, legs and scapes glabrous and sparsely punctate.
Hairs white, very long and erect or suberect on the body, more reclinate on the legs and scapes.
Body dark reddish brown; mandibles, antennae, legs, neck, base of petiolar peduncle and tip of gaster yellowish red; middle portions of femora, tibiae and scapes brownish.
Female (deàlated). Length 2.6 mm.
Differing from the worker only in the usual structural characters, in the somewhat shorter epinotal spines, which are slightly curved inward and further apart than in the worker, in the more convex petiolar node and in the sculpture, the pro-notum, mesonotum, scutellum and pleurae being coarsely longitudinally rugose like the upper surface of the head. Color and pilosity the same as in the worker.
Described from a single female and six workers (No. 15199, U. S. Nat.
1910.] Wheeler, Three New Genera of Myrmicine Ants. 265
Mus. Coll.) taken by Messrs. Schwarz and Barber at Cacao, Trece Aguas in Alta Vera Paz, Guatemala. This ant is evidently a timid species, living in small concealed colonies like the species of Rogeria and Leptothorax.
Lachnomyrmex seems to be related to Apsychomyrmex, Calyptomyrmex and Agrœcomyrmex gen. nov., to which I refer the peculiar Myrmica duis-burgi described by Mayr from the Baltic amber. The differences between Lachnomyrmex and Apsychomyrmex will be readily appreciated by comparison of Figs. 2 and 3. Calyptomyrmex and Agrœcomyrmex both have deep antennal scrobes above the eyes, but the former differs from Lachnomyrmex in having 11-jointed antennse, an unarmed thorax and a very different type of pilosity; while Agrœcomyrmex does not have a 2-jointed antennal club, the eyes are near the posterior corners of the head and the tip of the gaster is directed forward as in the Ponerine genera Proceratium Sysphincta, Bradoponera, Discothyrea and Alfaria.