Camponotus pylartes

Described from seven soldiers, numerous workers and a single female taken June 26 from a nest in a dead hickory branch (Hicorea myristicaeformis) at Delvalle, near Austin, Texas. I have also taken single workers running on the leaves and twigs of walnut trees near Austin and at New Braunfels, Texas. Among the specimens captured at Delvalle are two individuals that are clearly intermediate in structure of head and size of body between the soldier and worker; in other words, they are true mediae. (Wheeler 1904)

Identification
Although closely related to Camponotus impressus, Camponotus pylartes is very distinct in the shape of the thorax in the soldier and worker, and in the coloration of the gaster which is not banded with yellow in these phases of the latter species.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.



Biology
Wheeler (1904) - workers of C. pylartes were occasionally seen running about singly on walnut leaves and twigs near Austin and New Braunfels. I was, however, unable to discover the nests in these localities. One day, while examining the dead limb of a hickory (Hicorea myristicaeformis) in the sandy post-oak woods at Delva1le, a few miles from Austin, I saw a worker run along the bark and enter a small round hole which a moment before had been closed by the circular head of a soldier. As soon as the worker had entered, the soldier moved forward and again closed the opening. Other workers were soon seen returning and anon disappearing into the nest after gently knocking at the living portal with their delicate antennae. This is an interesting demonstration of the existence of a purely tactile communication between ants, since the soldier's eyes and antennae are in such a position when the head is in the opening that sight and smell cannot be employed for the perception of workers approaching either from without or within the nest. Inasmuch as the soldier steps aside only when the tactile signal is given, that is, when the flat, truncated forehead is titillated by an incoming, or the tip of the gaster by an outgoing worker, and not when these surfaces are touched with a pin or a straw, we must suppose that some very simple form of tactile communication has been developed in these insects pari passu with the extraordinary adaptation of the soldier as sentinel and animated front door in one.

When the hickory limb was broken in two, the nest was found to consist of a number of irregular galleries, apparently in great part the abandoned tunnels of some beetle larva, immediately under the bark. The galleries contained larvae and nude pupae, besides a few dozen workers and soldiers and a single virgin female. I was unable to ascertain whether this nest was merely one of several belonging to a single colony spread over different parts of the tree, but on still further breaking the limb, which was only about two feet long and one and one half inches in diameter, I found it to contain also a fine nest of C. etiolatus of essentially the same structure as the pylartes nest, except that the galleries extended into the hard wood, and a populous nest of Camponotus marginatus also excavated in the hard wood. Certainly these three species must have been very tolerant to excavate their nests in such close proximity to one another. In the bark of the same and surrounding trees I found nests of Macromischa subditiva, much like the nests of Leptothorax canadensis in our northern trees, and of L. affinis in Europe.

Nomenclature

 *  pylartes. Camponotus (Colobopsis) pylartes Wheeler, W.M. 1904b: 147, fig. 4 (s.w.q.) U.S.A. Petralia & Vinson, 1980: 386 (l.). Current subspecies: nominal plus fraxinicola.

Worker
Major Length, 4.5-5 mm.

Head subcylindrical, somewhat longer than broad, decidedly wider in front than behind, with inflated cheeks; occipital border straight or slightly concave. Anterior truncated surface oblique, in profile distinctly concave, with a sharp border only on the sides of the face and mandibles; on the clypeal and adjacent regions the truncated passes into the dorsal surface through a rounder angle than in impressus. Mandibles larger than those of impressus, with more convex ventral margins; blade with four distinct apical teeth and a toothless basal portion. Eyes, clypeus, frontal carinre and antennre as in impressus. Thorax distinctly narrower and less robust, the pronotum being fully as long as broad and forming an ellipsoid with the mesonotum when seen from above; dorso-ventral diameter of the pro- and mesonotum much shorter than in impressus. The mesoepinotal constriction is shallower, though pronounced, the angle formed by the basal and dec1ivous surfaces of the epinotum is more acute, and the former surface is longer and flatter. Petiole low, robust, as broad above as below, its anterior and posterior surfaces straight and parallel, the former passing over roundly into the flat top of the node when seen in profile; from above the node is convex in front and flattened behind. From behind it is somewhat more distinctly impressed in the middle above than in impressus. Gaster and legs as in that species.

Mandibles and anterior third of head subopaque, the former obscurely longitudinally rugose-punctate, the latter regularly and coarsely reticulate-rugose, with punctate interrugal spaces. Posteriorly this sculpture passes gradually into shallow and more scattered, umbilicately punctate foveolae on the front and cheeks. Posterior half of head and remainder of body shining, finely shagreened.

Hairs yellowish, short, erect and obtuse on the anterior half of the head, except its truncated surface, longer and tapering on the front and vertex. Gaster with scattered tapering hairs which are most abundant on the terminal segments. There are a few hairs at the tips of the antennal scapes and femora, and minute, appressed white hairs on the femora and tibiae.

Thorax and appendages yellowish brown; posterior two-thirds of head dark brown, gaster black, with the basal fourth of the first and second and sometimes of the third segment, yellow. Femora, tibiae and upper surface of the thorax sometimes darker than the lower portions of the thorax. Mandibular teeth black.

Minor Length 3-4 mm.

Mandibles when closed more projecting than in impressus. Clypeus and anterior portion of head less convex. Antennal scape surpassing the posterior angle of the head by nearly half its length. Thorax resembling that of the soldier, low through the pro- and mesonotum, which are also narrower than in the worker impressus. Basal epinotal surface long and flattened, the declivity shorter and concave, the two surfaces meeting at a right angle. Petiole and legs as in the soldier. Gaster proportionally shorter and more pointed.

Shining throughout and finely shagreened, the front and cheeks also faintly and sparsely punctate, the sculpture throughout being somewhat fainter than in the worker impressus.

Hairs white, sparse; long and erect on the clypeus, front and gaster, minute and appressed on the cheeks and legs.

Yellowish brown; head, gaster, apical third of funiculus, femora and tibiae, dark brown or black; base of first and second gastric, segments, mandibles, anterior portions of cheeks and clypeus, yellow.

Queen
Length 5.5 mm.

Head resembling that of the soldier, but somewhat more slender, with ocelli, slightly larger eyes and less inflated cheeks. Thorax hardly two and one half times as long as broad, mesonotum about as broad as long. There is a close resemblance to the soldier in the sculpture and pilosity. Anterior half of head brownish yellow with dark brown clypeal sutures and external mandibular borders. Teeth of mandibles black. Posterior half of head dark brown. Thorax and petiole yellow, pro- and mesonotum, scutellum and pleurae clouded with pale brown. Gaster black, basal and dorsal half of first and second segments, basal fourth of third segment and entire ventral portions of first and second segments, pale yellow. Coxae yellow, remainder of legs and antennae brown. Wings whitish hyaline, with pale yellow veins and stigma.

Type Material
Described from seven soldiers, numerous workers and a single female taken June 26 from a nest in a dead hickory branch (Hicorea myristicaeformis) at Delvalle, near Austin, Texas.