Myrmelachista ramulorum

Wheeler reported Myrmelachista ramulorum as being found in rather populous colonies in the hollow twigs of trees, especially in the sea-grape (Coccoloba uvifera) and "torchuelo" (Bucida buceros). The workers move about in long files.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Dominican Republic, Puerto Rico.

Nomenclature

 *  ramulorum. Myrmelachista ambigua subsp. ramulorum Wheeler, W.M. 1908a: 155, pl. 11, figs. 9, 10 (w.q.m.) PUERTO RICO. Wheeler, G.C. & Wheeler, J. 1953c: 138 (l.). Raised to species: Wheeler, W.M. 1934g: 189. Current subspecies: nominal plus fortior.

Worker
Length 2-2.3 mm.

Head a little longer than broad, suboblong, with slightly concave posterior border and slightly convex sides. Eyes flattened, near the middle of the head. Mandibles 5-toothed, the first, second and fourth tooth longest. Clypeus narrow, convex, with rounded anterior border, projecting in the middle. Frontal area large, very shallow and indistinct. Frontal groove short. Antennae short, 9-jointed; tips of scapes reaching only a short distance behind the eyes; first funicular joint nearly as long as the combined four succeeding joints, which are small and much broader than long; terminal joint as long as the two preceding joints of the club together. Pro- and mesonotum hemispherical from above, a little longer than the epinotum; mesoepinotal constriction pronounced on the sides, shallower above; epinotum longer than broad, narrowed in front, its basal surface somewhat flattened, in profile passing through a rounded angle into the shorter, sloping declivity. Petiole from above 1 1/2 times as long as broad, scale distinctly inclined forward, thick. below but becoming more attenuated above in profile; its upper border from behind transverse and feebly excised in the middle. Gaster elliptical. Legs rather stout, with somewhat incrassated femora.

Glabrous and shining. Mandibles subopaque, finely and sparsely punctate. Sides of head with a few coarse, scattered piligerous punctures. Gaster very feebly and finely reticulate.

Hairs yellow, suberect and sparse, longer on the body, shorter on the legs and antennal scapes; on the scapes confined to the anterior surface. Pubescence absent.

Yellowish red; gaster black., with narrow pale margins to the segments; head black. behind shading into red on its anterior third. Antennae and legs yellow; the clubs of the former and the middle portions of the femora, more or less infuscated.

Queen
(dealated). Length 3.3-3.5 mm.

Head 1 1/2 times as long as broad, oblong, with straight posterior and straight, parallel lateral borders. Eyes large, flattened, a little in front of the middle of the head. Mandibles and antennae like those of the worker, but the first funicular joint is much shorter than the four succeeding joints together. Thorax regularly elliptical from above, nearly twice as long as broad, broader than the head; in profile flattened above. Epinotum small and sloping, without distinct basal and declivous surfaces. Petiole resembling that of the worker, but with a proportionally lower and much blunter node.

Pilosity like that of the worker. .

Color variable, judging from two specimens; in one it is like that of the worker, but with the mesonotum and pleurae dark brown; in the other (possibly immature) the head and thorax are reddish yellow, with only the ocellar triangle blackened.

Male
Length 2-2.3 mm.

Head through the eyes broader than long, rounded behind, with short cheeks and moderately convex eyes and ocelli. Mandibles with two teeth, the apical smaller and more acute than the basal. Antennae 10-jointed, resembling those of the worker but with the club 4-instead of 3-jointed; scapes long, first funicular joint incrassated, as long as the three succeeding joints together; three basal joints of club subequal, longer than broad, terminal joints as long as the two preceding joints together. Thorax very broad and robust, nearly twice as broad as the head, elliptical, about 1 1/2 times as long as broad. Mesonotum rounded in front, much higher than the small pronotum, much flattened above and behind. Epinotum small, with a distinct but rounded angle between the subequal base and declivity. Petiole with a low, blunt node. Gaster elongate elliptical, flattened above. with prominent genital valves, the outer pair being triangular, twice as long as broad at the base and rounded at the tip, the median pair slender, linear and directed downward and forward, the inner pair very long, cultrate, directed backward and turned upwards at their tips. Legs slender, femora not incrassated.

Sculpture like that of the worker and female.

Body and appendages, with the exception of the antennal funiculus destitute of hairs and pubescence.

Piceous; mandibles, legs, antennre, scutellum, petiole and genitalia, except the outer valves, sordid yellow. Wings whitish hyaline, with very pale yellow veins.

Additional References

 * [[Media:Blum & Wilson 1964.pdf|Blum, M. S.; Wilson, E. O. 1964. The anatomical source of trail substances in formicine ants. Psyche (Cambridge) 71:28-31. [1964-05-05] PDF]]