Lachnomyrmex scrobiculatus

Lachnomyrmex scrobiculatus is a relatively common species. Workers and gynes occur in samples of sifted leaf litter from the forest floor in different elevations (100–1100m). Michael Kaspari collected a specimen at a barley bait in the La Selva successional plots, Costa Rica (Longino 2007).

Identification
Feitosa and Brandão (2008) - Body densely covered by continuous irregular rugae; metanotal groove obsolete; teeth of propodeal lobes widen basally; petiolar node subtriangular; dorsum of postpetiole convex and strongly rugose; first tergite of gaster entirely covered by long flexuous hairs.

This species is uniquely characterized by the pattern of sculpturation, absence of an impressed metanotal groove, and the presence of the small subpostpetiolar process. Gynes are somewhat more generalized morphologically (see Lachnomyrmex pilosus).

Distribution
Southern Mexico (Chiapas) throughout continental Central America to southern Panama.

Distribution based on Regional Taxon Lists
Neotropical Region: Belize, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Panama.

Nomenclature

 *  scrobiculatus. Lachnomyrmex scrobiculatus Wheeler, W.M. 1910a: 263, fig. 3 (w.q.) GUATEMALA. Wheeler, G.C & Wheeler, J. 1989a: 321 (l.). See also: Feitosa & Brandão, 2008: 40.

Worker
Feitosa and Brandão (2008) - Lectotype worker. HL 0.65; HW 0.61; ML 0.17; SL 0.38; EL 0.12; WL 0.75; PSL 0.19; PL 0.33; PPL 0.16; GL 0.80; TL 2.86; CI 95; SI 61; OI 19. Workers (n=18). HL 0.60–0.66; HW 0.58–0.65; ML 0.17–0.22; SL 0.36–0.40; EL 0.12– 0.15; WL 0.69–0.76; PSL 0.14–0.19; PL 0.27–0.33; PPL 0.14–0.18; GL 0.74–0.87; TL 2.80–2.99; CI 95–100; SI 58–64; OI 19–24.

Color dark brown to black, with appendages lighter. Body densely covered by vermiculate and somewhat thick rugae, transverse on anterior portion of pronotum, grading to longitudinal on rest of promesonotum, metapleura and lateral faces of propodeum; rugae somewhat longer and longitudinal on head dorsum and relatively sparser on metapleura and lateral faces of propodeum; mandibles with short striae restricted to the most basal portion; in dorsal view, metanotal area with long transversal rugae extending laterally towards metapleura; petiole and postpetiole irregularly rugose. Abundant pilosity, except by dorsal surface of propodeum; petiolar node, dorsum of postpetiole and first gastral tergite covered by long flexuous hairs; pilosity on first tergite of gaster concentrated at the most dorsal portion. Head usually slightly longer than broad, with vertexal margin minimally convex; frontal lobes relatively well developed and laterally rounded; eyes with about six facets on maximum diameter. Promesonotum moderately convex in profile; metanotal groove obsolete; propodeal spines straight; teeth of propodeal lobes well developed and considerably swollen basally, reaching propodeal spines half-length. Petiolar node elevated and subtriangular, in lateral view; postpetiole strongly convex and with a discrete anteroventral projection.

Queen
Feitosa and Brandão (2008) - (n=5). HL 0.66–0.68; HW 0.65–0.66; ML 0.22–0.24; SL 0.38–0.42; EL 0.16–0.19; WL 0.87–0.88; PSL 0.17–0.20; PL 0.31–0.33; PPL 0.17–0.20; GL 0.96–1.10; TL 3.23–3.36; CI 96–99; SI 57–65; OI 24–29.

Similar to worker; body pilosity considerably denser; eyes with about 12 facets at greatest diameter; wings with the basic pattern of venation for the genus; petiolar peduncle somewhat elongate; petiolar node faintly lower than in the conspecific worker.

Etymology
Feitosa and Brandão (2008) - The species name refers to the presence of the deep antennal scrobes, observed by Wheeler (1910) in the original description of Lachnomyrmex.