Lachnomyrmex scrobiculatus Wheeler, 1910

Feitosa, Rodrigo M. & Brandão, Carlos Roberto F., 2008, A taxonomic revision of the Neotropical myrmicine ant genus Lachnomyrmex Wheeler (Hymenoptera: Formicidae), Zootaxa 1890, pp. 1-49 : 40-41

Lachnomyrmex scrobiculatus Wheeler, 1910

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, Río Penas Blancas, 2.iii.2004, J.T. Longino col., no. INBIOCRI000005395 (1 worker) [ INBC]; Río San Lorencito, 1990, P. Hammond col. (6 workers) [ BMNH]; same data (1 worker) [ MZSP]; Guanacaste: Estr. Pitilla, 9km S Sta. Cecília, i.1991, I Curso Microhym., nos. INBIOCRI000305058/ INBIOCRI000384713 (2 workers) [ INBC]; same locality, 3–18.x.1991, P. Ríos 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]; Limón: 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: Península Osa, Aenn. Fund. Neotrop., 23.vi.1997, R. Anderson col., nos. 18686/18687 (1 worker and 1 gyne) [ WPMC]; Cerro Helado, 15km NE Rincón, 24.vi.1997, R. Anderson col., no. 18689 (1 gyne) [ WPMC]; PANAMA: Canal Zone: Barro Colorado Island, 1976, S. Levings col. (1 worker) [ MIZA].

Figures

FIGURE 16. Worker of Lachnomyrmex scrobiculatus from Heredia, Costa Rica: A, head in full face view; B, lateral view; C, dorsal view. Image by April Nobile, specimen CASENT 0103243.

FIGURE 19. Distribution maps for the Lachnomyrmex species (L. haskinsi, L. mackayi, L. nordestinus, L. plaumanni, L. regularis, and L. scrobiculatus).