Camponotus corniculatus

The type specimens were collected from a colony nesting in a hollow twig.

Identification
This ant is, perhaps, only a subspecies of Camponotus hippocrepis, described by Emery (1920) from a single defective minima taken by Balzan at Salinas sul Beni, Bolivia. Emery's figure and brief description agree with my specimens, except in indicating that hippocrepis has a much shorter and shallower mesoepinotal impression and differently shaped petiolar scale. The latter is described as depressed, with the dorsal surface broad and flat. Furthermore, the frontal carinae of corniculatus are neither widely separated nor parallel, as in Emery's species. Both species are closely related to Camponotus raphaelis Forel of Costa Rica, which I know only from the original description. Like Camponotus sanctaefidei, the maxima of corniculatus shows in the shape of its head a significant approximation to certain species of the subgenus Colobopsis. (Wheeler 1934)

Distribution based on Regional Taxon Lists
Neotropical Region: Guyana.

Nomenclature

 * . Camponotus (Myrmocladoecus) corniculatus Wheeler, W.M. 1934g: 236, fig. 6 (s.w.q.) GUYANA.
 * [Camponotus corniculatus Wheeler, W.M. 1934e: 424. Nomen nudum.]
 * Combination in C. (Myrmocladoecus): Mackay & Mackay, 2018: 24.
 * Status as species: Kempf, 1972a: 55; Bolton, 1995b: 94; McArthur, 2012: 14, 205.

Worker
minima Length 2.2-2.5 mm.

Resembling the media, but the head is much smaller and, without the mandibles, not longer than broad, with the sides more converging anteriorly and smaller, more convex and more posteriorly situated eyes. Clypeus trapezoidal, broader in front than behind, very convex and distinctly carinate in the middle, without posterolateral ridges, its anterior border broad, entire, feebly sinuate on each side. Scapes extending about two-fifths their length beyond the posterior border of the head. Thorax, with laterally sharply marginate pro-, meso- and epinotum; pronotum not more than one and one-half times as broad as long, flattened above; mesonotum also very fiat, sloping backward and downward and forming an obtuse angle with the pronotum in profile; epinotum horizontal, more concave above than in the media with more elevated, convex and anteriorly converging sides, so that it appears crescentic and with more acute inwardly curved posterior teeth; in profile the base rises above the highest level of the promesonotum so that the declivity is longer, steeper and more concave. Petiole much as in the media but the sides even more concave, the dentate corners of the superior border more pronounced and the posterior peduncle-like extension somewhat longer. Legs and antennre longer; gaster shorter.

Sculpture finer; surface of body smooth and shining with fine, sparse, piligerous punctures; only the gaster distinctly coriaceous. Pilosity proportionally longer, especially on the thorax; cheeks with ordinary, sparse, pointed hairs, some of which are appressed as in the media. Color much as in the maxima and media but the pronotum darker brown above and the yellow portions of the head and thorax more brownish.

media Length 3 mm.

Very similar to the maxima, but the head is smaller and very nearly as broad as long. Clypeus similar but sub carinate at the base and with the posterolateral ridges slightly less developed. Antennal scapes longer, extending about one-fourth their length beyond the  posterior border of the head. Pronotum smaller and narrower, the base of the epinotum distinctly concave above, with its lateral borders more elevated, the posterior excision deeper and the lobes more acute and dentiform, with more pronounced inward curvature. Petiole very similar to that of the maxima but the sides are more concave and the teeth at the lateral corners of the superior border are more distinct.

Sculpture, pilosity and color much as in the maxima, but less distinctly coriaceous, the erect hairs on the thorax longer and more abundant, those on the cheeks and clypeus shorter and more appressed; yellow portions of head confined to the mandibles, clypeus and anterior borders of cheeks.

maxima Length 3.3 mm.

Head subrectangular, distinctly longer than broad, somewhat narrower in front than behind, with very feebly convex posterior border, straight sides and slightly rounded cheeks; posterior and anterior corners not sharp; in profile the anterior surface of the head is subtruncate, the dorsal surface convex. There are no ridges from the eyes to the posterior corners. Eyes large, moderately convex, as long as their distance from the posterior border of the head. Mandibles stout, somewhat geniculate at the base, with very convex external borders and five acute teeth, the basal four well-developed. Clypeus large, subquadrate, flat, nearly as long as broad, surrounded by a deep suture; behind and parallel with its raised lateral borders there is on each side a blunt longitudinal, ridge-like projection, corresponding to the more pronounced protuberance in Camponotus sanctaefidei. Anterior border of clypeus straight in the middle, forming a short transverse lobe, because it is rather deeply excised on each side. Frontal area distinct, trapezoidal, fully twice as broad as long; anterior halves of frontal carina straight and strongly diverging, posterior halves straight and slightly converging behind; frontal groove distinct. Antennae rather stout; scapes extending twice their greatest diameter beyond the posterior border of the head. Thorax stout; pronotum large, excluding the neck twice as broad as long, flattened in the middle, semicircularly rounded anteriorly, the sides only bluntly marginate; mesonotum very regularly elliptical, nearly one and one-half times as broad as long, raised above the posterior end of the pronotum anteriorly and especially at the sides which are bluntly marginate, its surface flattened, sloping backward and downward to the long and deep mesoepinotal impression, bearing the large, prominent metathoracic spiracles, which are separated by a distance equal to twice the length of the impression. Base of epinotum rising very abruptly above the impression to the height of the promesonotum and forming a trapezoidal plate, broader behind than in front, with straight, submarginate anterior and lateral borders and broadly excised posterior border, the corner of which are produced backwards as short, flattened, distinctly in-turned lobes; declivity steeply sloping and deeply concave, as long as the base. Petiole shaped much as in sanctae-fidei; from above trapezoidal, twice as broad as long, with straight anterior, posterior and anteriorly converging lateral borders, the posterior corners acute; in profile the anterior surface is slightly concave, forming a distinct angle with the dorsal surface which is transversely convex and slopes upward and backward to the rather blunt, narrow and transversely rounded superior border, which terminates on each side in a sharp, tooth-like angle, the sides of the border concave, converging inferiorly. The petiole has a short but distinct posterior extension or peduncle. Gaster rather large, oval, broader in front than behind, the anterior surface of the first segment rounded, with a very distinct articular condyle but without a median impression for the accommodation of the petiolar scale. Legs rather long, fore femora somewhat enlarged.

Shining; finely coriaceous; mesonotum, mesopleurae, metapleurae and petiole more coarsely, almost reticulate rugulose, the base of the epinotum somewhat longitudinally, the dorsal surface of the petiole transversely, striate. Mandibles indistinctly shagreened, with fine piligerous punctures; clypeus, cheeks and front with coarse, shallow, sparse punctures; gaster very finely and transversely coriaceous, and like the posterior portion of the head, the promesonotum, legs and scapes with sparse piligerous punctures.

Hairs yellowish, abundant, rather coarse, of uneven length, long and erect on the head, thorax and gaster, shorter and more oblique on the scapes and legs, where they are most numerous on the extensor surfaces; on the cheeks and clypeus short and blunt; pubescence undeveloped.

Brownish yellow; mandibular teeth, posterior two-thirds of head, the mesonotum, mesopleurre, base of epinotum and anterior half of metapleurae and the petiole, except its ventral surface, deep piceous brown; gaster, extensor surfaces of femora and some irregular spots on the pronotum, paler brown.

Queen
Length 5.5-6 mm.

Head very similar to that of the maxima, but the eyes are larger and more convex, the clypeus broader and more hexagonal, with the posterolateral ridges well-developed. Antennal scapes extending three times their greatest diameter beyond the posterior corners of the head. Thorax of the usual shape in Camponotus females, subelliptical from above, more than twice as long as broad; mesonotum as broad as long, epinotum short, convex, slightly sloping, the declivity of about the same length, abrupt, very concave, the incurved teeth of the worker forms represented by a pair of blunt, feeble protuberances. Petiole resembling that of the maxima but higher and broader, the boundary between its anterior and dorsal surfaces more rounded, the latter transversely convex, the superior border bluntly angular and produced upward in the middle, without lateral teeth; the sides straight. Gaster large, elongate-elliptical, parallel-sided in the middle. Wings very short, measuring only 4 mm.

Smooth and shining; finely but distinctly coriaceous like the maxima, with scattered piligerous punctures; meso- and metapleurae and petiole more opaque and more coarsely coriaceous, the petiole regularly transversely striate. Coarse punctures on the cheeks, clypeus and front and the pilosity as in the maxima. Dark piceous brown; mandibles, clypeus, anterior borders of cheeks, antennae, middle and hind coxae and trochanters and ventral portion of petiole brownish yellow; pronotum and legs pale brown; the middle and hind femora and tibiae darker; wing-insertions and posterior borders of gastric segments sordid yellow. Wings rather opaque, whitish, with brownish yellow veins and pterostigma.

Type Material
Described from 23 specimens (a maxima, a media, 16 minimae and five females) taken by Mr. H. O. Lang at Kurupung, British Guiana, Nov. 1922, from a single colony nesting in a hollow twig.

References based on Global Ant Biodiversity Informatics

 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).