Stegomyrmex

A small genus of rarely observed Neotropical ants. The cryptic and slow moving foragers of this genus contain soil particles on their integument, a feature that further camouflages their presence. These ants were once thought rare but like many neotropical leaf litter ants have been shown, with the use of more and better litter sampling, to be more common than previously believed.

Biology
Feitosa et al. (2008) - Diniz and Brandao (1993) were the first to describe the nesting habits of Stegomyrmex, Based on observations on colonies of Stegomyrmex vizottoi from Mirassol, state of Sao Paulo, Brazil, describing nest architecture, population distribution among nest chambers, different worker behaviors at each part of the nest, and the foraging habits of the workers, which exploit the environment surrounding their nests singly, searching for myriapod eggs.

Nomenclature

 *  STEGOMYRMEX [Myrmicinae: Stegomyrmecini]
 * Stegomyrmex Emery, 1912b: 99. Type-species: Stegomyrmex connectens, by monotypy.

Worker
Feitosa et al. (2008) - Monomorphic. 5 to 6.5 mm in length. Reddish brown to black. Integument thick, shining and in general densely areolate, except for Stegomyrmex bensoni. Pilosity conspicuous and bizarre; hairs varying from short, subdecumbent and filiform to long, suberect, and variably branched; mandibles sparsely covered by long filiform hairs; anterior margin of clypeus bearing one or two pairs of very long setae, reaching half the length of mandibles, but without an isolated median seta; appendages covered by short decumbent hairs and by a fine and dense appressed pubescence; inferior corners of pronotum with a dense row of plumose hairs.

Head subtrapezoidal with vertexal margin slightly depressed to slightly convex; occipital corners angulate; broader posterad. Palpal formula 2:2. Labrum bilobed. Mandible triangular, long, strongly curved down apically and with the blades crossing apically when mandibles are closed; masticatory border multidenticulate (total dental count 12–15), with the apical tooth longer than the preceding ones. Median portion of clypeus narrow, flat and vertical, not bicarinate, quite narrowly inserted between the frontal lobes. Frontal lobes enormously expanded anterolaterally and projected far out over the lateral portions of clypeus and mandibles. Each frontal lobe covering dorsally a very deep antennal scrobe; in full face view, space between frontal lobes narrowest near the middle of head, revealing the compound eyes; clypeus and basal portion of mandible entirely concealed by the frontal lobes. Frontal area impressed, glabrous and smooth, the anterior suture obsolete. A shallow groove, almost devoid of any sculpture, present on each side of the head dorsum, extending from the frontal area to the occipital corner of head, the two grooves meeting anteriorly, forming a noticeable V. Antenna with 12 segments, with a three-segmented club; antenal scape slender, curved basally and broader at apex. Compound eye exceedingly small, oval in shape, almost indistinct from the integument sculpture; placed on the sides of head immediately beneath the antennal scrobe, but visible when head is in full face view.

Mesosoma, in dorsal view, slender, widest at the level of the anterior area of pronotum. Promesonotum evenly rounded in profile, dome-like; anterosuperior corner of anepisternum set much lower than the adjacent surface, forming a deep fovea; promesonotal suture almost obsolete in some individuals. Mesonotum elongate with posterior portion sloping down; metapropodeal impression relatively broad and usually shallow, except for S. bensoni.

Propodeum, in side view, variably convex dorsally, and with the declivity sinuous; propodeal spiracles low on side and raised in prominent, subcylindrical protuberances; propodeal spines short and more or less acute; propodeal lobes large and usually projected over the petiolar peduncle. Legs relatively long; femora and tibiae moderately incrassated; tarsal claws simple; metatibial spurs absent.

Petiole long and pedunculate, with about twice the length of the postpetiole; petiolar node variably convex in profile; ventral carina present and bearing 0–2 blunt anterior projections. Postpetiole approximately as long as broad, globose, without ventral process. Gaster oval, without basal shoulder; tergite of abdominal segment IV (first gastral) not broadly overlapping sternite on gaster ventral surface.

Sting apparatus. Spiracular plate with spiracle placed ventrally; anal plate with several sensillae; lancet with a pair of functional valves; furcula with indistinct dorsal arms.

Queen
Feitosa et al. (2008) - Like conspecific worker, with the modifications expected for myrmicine gynes. Anterior ocellus slightly larger than posterior ones. Notauli and parapsidial lines usually indistinct from surrounding sculpture; prescutellum with central area indistinct, scutoscutellar sulcus shallowly impressed, with transversal rugulae varying in number and forming distinct cells; lateral wing of prescutellum not projecting laterally; scutellum semicircular, with its posterior half always sloping down and with posterior border concave; propodeal spines shorter than in conspecific workers.

Forewing with distinct and strongly colored stigma; longitudinal veins Sc+R, SR, M+Cu, and A present. Cells R, Cu and 1M closed. Hind wing with Sc+R extending shortly beyond point where they connect to M, which extends as a tubular vein up to the wing distal border; Cu cell closed and very short; six to eight submedian hamuli.

Male
Feitosa et al. (2008) - Dark brown to black, with appendages and gaster usually lighter. Integument densely sculptured, opaque or nearly so, except for the postpetiole and gaster which are smooth and shining; appendages very finely punctate. Pilosity composed of fine hairs, whitish to golden, mostly curved or suberect on body, sparser on metasoma. Apressed pubescence on antennae and legs.

Head broadest across compound eyes, narrowed anteriorly; median portion of vertexal margin usually weakly convex; occipital corners rounded; ocelli prominent. Mandible relatively developed and subtriangular; masticatory border multidenticulate, with the apical tooth much more developed than the others. Clypeus broad. Frontal lobes not so developed as in the conspecific gynes and workers, but concealing the antennal insertions, forming a short and shallow antennal scrobe. Antennae long and slender with 13 segments; scapes relatively short.

Mesosoma robust; prescutellum separated from scutellum by an impression with short longitudinal rugae. Scutellum narrow posterad. Metanotum narrow, with blunt median tumosity. Propodeum dorsal face flat, steeply sloping posterad, unarmed. Legs slender, middle and hind tibiae without apical spurs; tarsal claws slender and simple. Wing venation as in the gynes.

Petiole clavate, pedunculate, and with a long, low, rounded node. Postpetiole as broad as long, attached to the gaster by almost its full width. Gaster elongate, with first segment occupying most of its length; visible apical segments subequal in length.