Workers and queens occur in samples of sifted leaf litter from the forest floor. Mike Kaspari collected a specimen at a barley bait in the La Selva successional plots.
Mexico, Guatemala (type locality), Costa Rica. Costa Rica: widespread in lowland wet forest, including the Osa Peninsula, Hitoy Cerere, La Selva Biological Station and surrounding Atlantic slope sites to 1000m, Penas Blancas Valley, and the Pitilla area of Guanacaste Conservation Area. Appears less common on Pacific side (one record from the Osa Peninsula, Ranch Quemado) than on the Atlantic side (many records).
Taxonomic history
Wheeler & Wheeler, 1989a PDF: 321 (l.).See also: Feitosa & Brandão, 2008 PDF: 40.Figures 16, 19
Lachnomyrmex scrobiculatus Wheeler , 1910: 263, fig. 3. Syntypes, GUATEMALA: Alta Vera Paz: Trece Aguas, Cacao, 24.iii.1906, E.A. Schwarz & H.S. Barber cols, no. 21059 (1 worker) [ MCZC ] (examined by images); same data; no. 13199 (1 worker) [ USNM ] (examined); same locality; 29.iii.1906, E.A. Schwarz & H.S. Barber col., no code data (1 worker) [ AMNH ] (examined); same locality, 4.iv.1906, E.A. Schwarz & H.S. Barber cols, no. 13199 (1 worker, here designated lectotype in order to improve nomenclatural stability) [ USNM ] (examined); same locality, 25.iv.1906, E.A. Schwarz & H.S. Barber cols, no. 13199 (1 gyne) [ USNM ] (examined); same locality, 26.iv.1906, E.A. Schwarz & H.S. Barber cols, no. 13199 (1 worker) [ USNM ] (examined); same data (1 worker) not located; Gotwald 1969: 106 (mouthparts).
Worker diagnosis. 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.
Lectotype measurements. 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.
Worker measurements (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.
Gyne measurements (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.
Worker description. 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.
Gyne. 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. The species name refers to the presence of the deep antennal scrobes, observed by Wheeler (1910) in the original description of Lachnomyrmex .
Comments. 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 comments under L. pilosus ).
In the description of the Lachnomyrmex sting apparatus (Kugler 1978), the author identifies the examined species as closely related to L. scrobiculatus . However, we have not examined this material, and thus it was not possible to confirm Kugler's identification.
Lachnomyrmex scrobiculatus is a relatively common species occurring from southern Mexico (Chiapas) throughout continental Central America to southern Panama. 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).
Additional material examined. BELIZE: El Cayo: Caves Branch, viii.1972, S. Peck & J. Peck col. (5 workers) [ MZSP ]; COSTA RICA: Alajuela: Casa Eladio, Rio Penas Blancas, 2.iii.2004, J.T. Longino col., no. INBIOCRI000005395 (1 worker) [ INBC ]; Rio San Lorencito, 1990, P. Hammond col. (6 workers) [ BMNH ]; same data (1 worker) [ MZSP ]; Guanacaste: Estr. Pitilla, 9km S Sta. Cecilia, i.1991, I Curso Microhym., nos. INBIOCRI000305058/ INBIOCRI000384713 (2 workers) [ INBC ]; same locality, 3-18.x.1991, P. Rios col., no. INBIOCRI000377966 (1 worker) [ INBC ]; Pitilla Field Station, 2.v.1995, R. Anderson col., no. 17722 (7 workers and 3 gynes) [ WPMC ]; same data (2 workers and 1 gyne) [ MZSP ]; same locality, 14.ii.1996, R. Anderson col., nos. 17739/17741 (3 workers) [ WPMC ]; Limon: P.N. Tortuguero, Cerro Tortuguero, ii.1993, R. Delgado col., nos. INBIOCRI001289301/INBIOCRI001289339 (2 workers and 1 gyne) [ INBC ]; same data, INBIOCRI001289337 (1 worker) [ MZSP ]; Puntarenas: Peninsula Osa, Aenn. Fund. Neotrop., 23.vi.1997, R. Anderson col., nos. 18686/18687 (1 worker and 1 gyne) [ WPMC ]; Cerro Helado, 15km NE Rincon, 24.vi.1997, R. Anderson col., no. 18689 (1 gyne) [ WPMC ]; PANAMA: Canal Zone: Barro Colorado Island, 1976, S. Levings col. (1 worker) [ MIZA ].
Chiapas, one specimen, soil. In Wheeler's original description and figure, the number of antennal segments is given as twelve. Dr. M. R. Smith and Dr. K. Yasumatsu have both called this count to question (in litt.), and the types in the Museum of Comparative Zoology show that there are really only eleven segments. The specimen taken by Dr. Goodnight compares well with the types in every respect. Wheeler related this genus to Agraecomyrmex from the Baltic Amber, but Agroecomyrmex seems entirely different, and possibly intermediate between the Ectatommini and the Myrmicini . Lachnomyrmex seems more closely related to Rogeria by virtue of the thoracic structure and the eyes, sculpture, and pilosity.
