Orthognathotermes Holmgren, 1910

Rocha, Mauricio Martins Da & Cancello, Eliana M., 2009, Revision of the Neotropical termite genus Orthognathotermes Holmgren (Isoptera: Termitidae: Termitinae), Zootaxa 2280, pp. 1-26 : 2-4

Genus Orthognathotermes Holmgren, 1910

Orthognathotermes Holmgren, 1910:286 .

Orthognathotermes ; Mathews, 1977:124 (redescription).

Type species: Mirotermes macrocephalus Holmgren, 1906 , by original designation.

Etymology: From the Greek “ orthos ” (rectilinear) + “ gnathos ” (mandibles), and the Latin “ termes ” (termite), in reference to soldier’s straight and elongated mandibles.

Imago. Head rounded in dorsal view, fontanelle at the level of posterior half of eyes, broad (fig. 16) or narrow (fig. 18), and large (fig. 20), medium (fig. 17), or small (fig. 18). Eyes large (fig. 18) or small (fig. 19), in profile, distant from the inferior margin of head by a distance equal or less than the larger diameter of the ocellus. Ocelli in dorsal view semicircular (fig. 16), reniform and narrowed (fig. 19), or reniform and large (fig. 18), in lateral view oval (fig. 16) or sub-triangular (fig. 20). Ocellus remote from the eye by distance equal to its minimum diameter (fig. 19), or less (fig. 17), or touching the eye (fig. 16). Postclypeus convex in lateral view, elevated above dorsal margin of head (fig. 16). Antennae with 17 articles: second half of first, third half of second, fourth one third larger than third, fifth one third larger than fourth, sixth through eighth enlarge successively, the others subequal (except in O. heberi : fourth through eighth enlarge successively, the others subequal; in O. aduncus and O. mirim , third and fourth half of second, fifth one third larger than fourth, sixth through eighth enlarge successively, the others subequal). Mandibles similar to those of the workers. Pronotum semicircular (fig. 23) to sub trapezoidal (fig. 19), anterior margin slightly concave and posterior emarginated, posterior margin of mesonotum and metanotum emarginated. Tibial spurs formula 3:2:2. Wings approximately twice the length of body. Head covered with scattered bristles and a mat of short hairs, varying in density in each species; labrum with 12 bristles in two rows (fig. 16) or not organized in rows (fig. 17). Antennae covered with short hairs and bristles. Pronotum covered with bristles and short hairs varying in density according each species. Abdominal tergites and sternites densely covered with bristles and short hairs, and with a row of bristles on the posterior margin. Legs covered with bristles and short hairs, with spines in the internal margins of tibiae. Wing scales covered with bristles, and the surface of wings with short hairs. Head capsule with three pale spots - two in front of the ocelli and one above the fontanelle - wing veins brown, wing cells pale brown and translucent.

Soldier. Head capsule sub rectangular in dorsal view, with sides parallel (fig. 2) or slightly convergent in front (fig. 7); posterior margin with or without longitudinal furrow (fig. 8); distinct prominence or lump (fig. 2, see arrow) in profile, less (fig. 15) or more salient (fig. 2); a flange near each antennal socket (fig. 1, arrow). Frontal pore and frontal gland indistinct. Mandibles curving downward in profile (fig. 1), very long and narrow, with a tooth-like projection near middle (fig. 6) or at proximal half (fig. 1), tips hooked inward, strongly hooked in the left mandible of O. uncimandibularis sp. nov. (fig. 11), lightly hooked in the other species; two basal teeth on left mandible and one on the right, sharp cutting edge on inner margin extends from the tooth-like projection to near tip, blades elbowed outwards at the same point level; circular section at the proximal part. Labrum with middle lobe distinct (fig. 1), except in O. mirim (without lobes, fig. 5 and O. brevipilosus , weakly trilobated,fig. 9). Ocellar spots appear only in O. wheeleri (fig. 3 arrow). Antennae with 15 articles: first longest, second half of first, third half of second, fourth and fifth equal to second, sixth one third longer than fifth, the others subequal and one third longer than sixth (except in O. okeyma and O. orthognathus : fourth and fifth one third longer than second, and sixth equal to second). Postmentum elongate, with concave lateral margins. Pronotum with anterior and posterior trapezoidal lobes, with emarginated margins, both lobes forming a close angle in profile. Tibial spurs formula 3:2:2. Pilosity of head variable in each species. Antennae covered with short hairs and bristles. Labrum: with variable number of bristles, forward oriented in median lobe, sparse and erect in the rest of the surface. Body covered with bristles and short hairs, variable according to species. Postmentum with two clusters of two to five bristles near the anterior margin, and short hairs and bristles scattered on the rest of the surface. Legs with scattered short hairs and bristles plus some spines on the internal margins of tibiae. Head orange in majority of individuals, but may vary from brown to yellow, mandibles ferruginous to black, body pale-yellow.

Worker. Morphologically uniform among species. Head rounded, Y suture invisible. Antennae with 15 articles, or if 14, the third subdivided. Anteclypeus, postclypeus and labrum similar in shape to those of imago. Pronotum with anterior lobe slightly larger than posterior, with an angle near 90º between them, anterior lobe slightly emarginate. Mandibles described below. Tibial spurs formula: 2:2:2. Fontanelle rounded and visible. Entire head covered with scattered bristles and very few short hairs. Pronotum with bristles and short hairs concentrated in anterior and posterior margins, mesonotum and metanotum with bristles and short hairs on posterior margins, abdominal tergites and sternites densely covered with short hairs and bristles, both with a row of erect bristles on posterior margins. Legs covered with scattered bristles and short hairs.

Worker/Imago mandibles (fig. 25). Left mandible: apical tooth twice the size of M1+2, an acute angle between apical and M1+2, a sinuous blade between M1+2 and M3, M3 much smaller than M1+2 and equidistant from the anterior point of M1+2 and the molar prominence, molar tooth conspicuous, molar prominence without ridges and very concave. Right mandible: apical tooth with more than twice the size of M1, M2 much smaller than M1, molar plate without ridges and very concave.

Digestive tube (fig. 24). Foregut: crop developed, without any constriction between it and the gizzard, cuticular armature of the gizzard complete with 24 visible folds, six of first order, six of second and 12 of third (fig. 28 A). Midgut: mixed segment with a long mesenteric tongue dorsally placed in right lateral view of the tube in situ (fig. 24 B). Two pairs of Malpighian tubules, each tubule with a distinct insertion on the junction mesenteron-proctodeum, on the opposite side of the mesenteric tongue of the mixed segment (fig. 28 B). Hindgut: P1 long, in ventral view, forming an arch from the left side of body through the right, circling P3 (fig. 24 C), going to the right side until the P2 and its insertion in P3 (fig. 24 B). This insertion is not visible as it is covered by P4 (fig. 24 B). P3 large, without any visible ornamentation at 400x magnification, P3a voluminous, P3b funneled, P4 long.

Enteric valve (figs. 26, 27): armature composed of six cushions of three kinds: three fully-developed cushions (dark large arrow), two medium-sized, with fewer spines (light arrow), and one reduced, with much fewer and smaller spines (dark tiny arrow). The largest three cushions are intercalated with the others, bearing finger-like projections covered with a few spines on the internal face, extending into the lumen of P3. That largest plate with bulbous base is on the opposite side of the most reduced plate.

Comments: the differences in figures are due to positioning of the parts in the slides.

Biology. Orthognathotermes is endemic to the Neotropical region, occurring in different vegetation zones, including the Brazilian Cerrado and dense tropical forests.

Information on the biology of Orthognathotermes species is rare, sparse, and some comes from field notes of collectors, as for instance, on the nest of O. heberi . This species may live in nests constructed by other species or build its own nests, that are low mounds, built with soft earth, and frequently extend several centimeters underground (Coles de Negret & Redford, 1982). Araujo (1977) describe a similar nest for O. insignis .

They probably feed on humus in subterranean galleries ( Mathews, 1977, Coles de Negret & Redford, 1982). The morphology of the workers mandibles (humivorous type) and the detection of sand particles in the gut are in agreement with this hypothesis.

Soldiers of Orthognathotermes have two types of defense mechanisms ( Mill, 1982): mechanical, by snapping/slashing mandibles and chemical, by viscous substance produced by the salivary glands and released in opponents by rupturing of the body wall and oral cavity. Mill (1984) reported that soldiers are capable of autolysis, breaking the body wall between the coxae and releasing a substance that becomes viscous in contact with air. Mathews (1977) mentioned that gland products are expelled through the mouth. We found a few soldiers with signs of rupture on their bodies, but some specimens exhibited a hardened secretion covering all pre-oral cavities and mandibles. It is not known which gland is responsible for the secretion; Mill (1984) stated that it is a salivary gland product, while Mathews (1977) mentioned at first that the secretion is a salivary gland product (p. 65–66), and in the genus redescription, that it is a frontal gland product (p. 128). We were not able affirm which species was examined by Mill in both papers, as only part of his material is housed in MZUSP.