Gesomyrmex kalshoveni

W. M. Wheeler was sent the specimens used for the description of this ant by a Dr. Kalshoven. Details of the collections and other remarks by Wheeler followed in a second paper about this species (Wheeler 1929): "The new Gesomyrmex was found in a branch of an Artocarpus elastica ("bendo") in a stand of various deciduous trees-relics of the old natural mixed forest-amidst the teak-forests of Semarang." This statement confirms my supposition in regard to the habits of Gesomyrmex, which evidently lives much like many twig-or branch-inhabiting Camponoti of the subgenera Myrmentoma, Colobopsis, Pseudocolobopsis, Hypercolobopsis, Myrmocladrecus and Myrmobrachys. That the specimens collected by Dr. Kalshoven were living in a piece of primitive forest is of some interest in connection with the fact that the extant species of Gesomyrmex are sporadic survivors, or relicts of an ancient ant-fauna of much wider distribution during the Oligocene Tertiary. Females from a second nest were found to be pupating without cocoons.

Identification
The new Gesomyrmex differs from Gesomyrmex howardi in the shape of the petiolar node, which in the latter is much thicker above, with rounded, entire border, in the epinotum which is shorter in howardi, with much less convex base and with the base and declivity subequal. The sculpture of howardi is decidedly coarser, especially on the epinotum and pleurae, so that the surface is more opaque. The color is also darker and more brownish or sordid than in kalshoveni and Gesomyrmex chaperi. There are distinct striae on the front in the media and minima of howardi.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia. Palaearctic Region: China.

Nomenclature

 *  kalshoveni. Gesomyrmex kalshoveni Wheeler, W.M. 1929a: 2, fig. 1 (s.w.) INDONESIA (Java). Wheeler, G.C. & Wheeler, J. 1953c: 140 (l.). Current subspecies: nominal plus gracilis. See also: Wheeler, W.M. 1929c: 91.

Worker
The variations in structure in all the castes are so finely graduated that there is no hiatus between the smallest specimen measuring 2.8 mm. and the largest measuring 6.6 mm.

maxima Length 5-6.6 mm.

Head subrectangular, about 1 1/4 times as long as broad, slightly narrower in front than behind, with the sides distinctly concave in front of the middle; the posterior border feebly concave, the posterior corners convex and rounded; the dorsal and gular surfaces rather flat. Eyes elongate, convex, scarcely reniform, with straight or very nearly straight internal and impressed posterior orbits, one-third as long as the head and well up on its dorsal surface. Ocelli minute, unpigmented, the anterior smaller than the two posterior, which are on a level with the posterior orbits of the eyes. Mandibles stout, convex, with strongly rounded external borders, 8-toothed, the first, second, fourth, sixth and eighth tooth, counting from the apex, larger than the others and rather blunt. Clypeus short and flat, its anterior border slightly and evenly rounded, scarcely projecting in the middle; its lateral portions not reaching the anterior corners of the head, convex but not auriculate. Frontal area distinct, moderately large and triangular; only a portion of the frontal groove developed in the middle of the head just anterior to the ocelli; frontal carinae widely separated, subparallel, rather erect and slightly lobular anteriorly, continued back to the anterior orbits of the eyes. Antennae 8-jointed; scapes curved basally, gradually thickened distally, their tips reaching somewhat beyond the middle of the eyes; funiculi distinctly enlarged apically, first joint twice as long as broad; second and third 1 1/2 times as long as broad, remaining joints nearly as broad as long, except the terminal joint which is somewhat longer. Thorax stout anteriorly, the pro- and mesonotum convex, forming together a hemispherical mass, separated by a distinctly impressed suture, rounded above in profile, the former as broad as long with a faint median longitudinal impression behind; the latter as long as broad, subcircular with straight posterior and rather deeply impressed anterior and lateral sutures. Behind the mesonotum the thorax is divided into two regions by a transverse dorsal furrow; the shorter anterior portion, representing the metanotum is depressed and bears the somewhat projecting metanotal spiracles at its sides ; the posterior portion, representing the epinotum, is as broad as long, with the base somewhat convex and bearing the epinotal spiracles at the middle of its sides. Posteriorly it passes into the distinctly shorter, sloping declivity, with which it forms a distinct, obtuse angle. Petiole small; its node from above transversely elliptical, nearly 1 2/3 times as broad as long; in profile distinctly cuneate, with convex anterior and posterior surfaces, the moderately sharp superior border transverse, feebly and broadly excised or sinuate in the middle. Gaster large, elongate-elliptical. Legs stout; all the femora somewhat thickened; spurs of middle and hind tibiae very short; tarsal claws large and stout.

Smooth and shining; mandibles coarsely punctate, with a few incomplete longitudinal rugules; head more finely punctate; median portion of clypeus, front and cheeks finely and longitudinally striate as far back as the eyes. Thorax, petiole, gaster and appendages very minutely and sparsely punctate, the gaster also very delicately and indistinctly, transversely coriaceous.

Hairs yellowish white, absent on the body, except at the tip of the gaster and on the mandibles, clypeus and front. On these latter regions they are numerous, short, erect, stubby and obtuse. Scapes with short oblique hairs. Pubescence undeveloped, except on the tibiae where it is very short, dilute and appressed.

Honey yellow; gaster and legs paler and more whitish yellow, the several gastric segments very faintly infuscated posteriorly; frontal carinae and mandibles red, the latter with black teeth and dental border ; impressions of the posterior orbits dark brown; claws and tarsal articulations reddish.

media Length 3.5-4.5 mm.

Differing from the maxima mainly in the characters of the head, which is proportionately smaller and only 1 1/6 to 1 1/5 times as long as broad; its posterior portion shorter and more rounded, its anterior portion more narrowed, with proportionally larger eyes, which are more convex, and reniform, i.e. with concave internal orbits and one half as long as the sides of the head. Posterior ocelli represented by minute pits in the larger, usually absent in the smaller specimens. Mandibles 7-8 toothed and more elongate and less convex than in the maxima, with less convex external borders and only the first, fourth and fifth tooth enlarged and more acute, the third, seventh and eighth very minute. Median portion of the clypeus longer, more convex posteriorly, its anterior portion more advanced and lobular, depressed. All the funicular joints longer than broad, except the penultimate. Thorax somewhat more slender than in the maxima, pronotum without longitudinal impression; mesonotum longer than broad, with more nearly parallel sides; its surface flattened and even slightly concave in profile. Petiole as in the maxima, but slightly more narrowed above.

In the larger media there are distinct striae and short stubby hairs on the front, though the latter are less numerous; in the small media these hairs are absent and the striae are very indistinct or obsolete. Color like that of the maxima, except that the mandibles are yellowish, with only the teeth blackish.

minima Length 2.8-3.2 mm.

Differing from the media in having a still shorter head, in the smallest minima scarcely longer than broad including the eyes, which ate more convex and laterally projecting, decidedly reniform and taking up more than 3/4 of the sides of the head, so that the cheeks and postocular regions are greatly reduced, the latter without distinct corners and with slightly and evenly convex median border. Clypeus much longer and anteriorly projecting, more convex behind and somewhat more concave in front, than in the media. Ocelli represented by a pair of very minute pits or completely absent. Mandibles more elongate, flattened, with straight external borders, the teeth forming a more even crowded series, the apical longer than the basal. Frontal carinae very short and indistinct. Antennal scapes extending to the posterior third or fourth of the eyes. Thorax more slender, pro- and mesonotum much less convex, with nearly straight outlines in profile, the latter feebly concave as in the media. Legs slender, but with the femora distinctly enlarged basally.

Mandibles pale yellow with reddish teeth ; posterior orbits not tinged with brown. In other respects like the small media. The larger minima is intermediate between the small minima and the small media even in the structure of the mandibular teeth.

Larva
The workers collected by Dr. Kalshoven were accompanied by several milk-white larvae of different sizes and a single semipupa. The larvae resemble those of other Formicinae in shape, but are almost hairless. The head is very small and subglobular, the mandibles minute, with only an apical tooth, which is drawn out into a slender, acute point. The semipupa measures a little over 7 mm. and is not enclosed in a cocoon. The semipupa is clearly a male. It has well-developed wing-pads and rudiments of the genital valves, and the imaginal head is sufficiently developed to enable me to determine its main peculiarities. As will be seen from the figure, it is broader than long, with evenly rounded, convex, postocular region; the eyes are very small, for a male, not longer than the cheeks, not very convex and situated at the sides of the head; the ocelli are moderately large but flat; the antennal insertions are very far apart and near the anterior orbits; the antennal scapes are short and abruptly bent outwards at their tips (probably a pupal character), the funiculi short, thick and distinctly 6-jointed (!), instead of 7-jointed as in the worker; the clypeus is rounded and slightly projecting in the middle; the mandibles small, narrow, edentate and rather blunt

Type Material
Described from 15 workers taken by Dr. L. G. K. Kalshoven in a teak-forest at Semarang, Java. The following are the lengths of the individual (alcoholic) specimens:

Maximae: 6.6 mm.; 5 :7 mm.; 5.3 mm.; 5 mm.

Mediae: 4.5 mm.; 4 mm.; 4 mm.; 4 mm.; 3.8 mm.; 3.8 mm.; 3.5 mm.; 3.5 m.m.

Minimae: 3.2 mm.; 3 mm.; 2.8 mm.

References based on Global Ant Biodiversity Informatics

 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Liu C, B. Guénard, F Hita Garcia, S. Yamane, B. Blanchard, and E. Economo. New records of ant species from Yunnan, China. Submitted to Zookeys
 * Wheeler W. M. 1929. The identity of the ant genera Gesomyrmex Mayr and Dimorphomyrmex Ernest André. Psyche (Cambridge) 36: 1-12.