Lachnomyrmex plaumanni

Feitosa and Brandão (2008) - This is species has been collected from northern Argentina to southeastern Brazil, along the submontane areas of the Brazilian Atlantic Forest (400–1200m). Despite the constant presence of L. plaumanni in leaf liter samples from the Atlantic Forest, all attempts to maintain colonies in artificial conditions so far have failed. Gynes and workers usually die a few days after capture. There is a single record of a L. plaumanni worker foraging in the vegetation. It was collected manually in a bromeliad fixed in a high live tree from Serra do Itapeti, state of São Paulo, Brazil (M.S. Morini, pers. comm.).

Identification
Feitosa and Brandão (2008) - Body sparsely covered by short, fine rugae; promesonotum elevated minimally above propodeum level; apex of propodeal spines curved downwards; teeth of propodeal lobes swollen and extremely reduced; dorsum of postpetiole with about six long hairs; first tergite of gaster entirely devoid of long flexuous hairs. Lachnomyrmex plaumanni is one of the smallest species in the genus and can be immediately recognized by the combination of sparse sculpturation, propodeal spines curved downwards, and dorsum of postpetiole with about six long hairs.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Brazil, Costa Rica.

Nomenclature

 *  plaumanni. Lachnomyrmex plaumanni Borgmeier, 1957: 125, figs. 47-52 (w.q.) BRAZIL. See also: Feitosa & Brandão, 2008: 34.

Worker
Feitosa and Brandão (2008) - Lectotype. HL 0.65; HW 0.63; ML 0.19; SL 0.38; EL 0.11; WL 0.71; PSL 0.14; PL 0.30; PPL 0.14; GL 0.79; TL 2.77; CI 97; SI 60; OI 17. Workers (n=58). HL 0.57–0.69; HW 0.57–0.68; ML 0.17–0.20; SL 0.35–0.42; EL 0.09– 0.14; WL 0.61–0.80; PSL 0.13–0.15; PL 0.25–0.35; PPL 0.11–0.14; GL 0.68–0.93; TL 2.51–3.07; CI 96–101; SI 56–65; OI 14–22.

Worker description. Color light reddish-brown to dark brown, with appendages lighter. Body sparsely covered by irregular short rugae, somewhat longer and longitudinal on head dorsum; mandibles with short longitudinal striae restricted to basal portion; petiole and postpetiole finely and irregularly rugose. Abundant pilosity on head and promesonotum dorsum; dorsum of petiolar node and postpetiole with about four and six long hairs, respectively; first gastral tergite entirely devoid of long flexuous hairs. Head as long as broad, with vertexal margin strongly convex; frontal lobes laterally rounded; eyes with about six facets on maximum diameter. Promesonotum moderately convex in profile, only discretely higher than level of propodeum; metanotal groove shallow to virtually obsolete; apex of propodeal spines distinctly curved downwards; teeth of propodeal lobes swollen and reduced, with less than one-third of propodeal spines length. Petiolar node moderately elevated, dorsally rounded, and with the posterior face weakly sloped in lateral view; postpetiole feebly convex dorsally and without ventral processes.

Queen
Feitosa and Brandão (2008) - (n=20). HL 0.58–0.71; HW 0.58–0.71; ML 0.17–0.25; SL 0.36–0.44; EL 0.13– 0.19; WL 0.73–0.91; PSL 0.13–0.16; PL 0.30–0.39; PPL 0.13–0.16; GL 0.79–1.02; TL 3.45–2.70; CI 97–102; SI 58–62; OI 21–28.

Differing from worker by the larger eyes, with around 12 facets at maximum diameter; propodeal spines relatively wider basally and with the apexes only minimally curved downwards.

Etymology
Feitosa and Brandão (2008) - Father Thomas Borgmeier (1957) named this species in honor of the Lithuanian entomologist, Fritz Plaumann (1902–1994), collector of the L. plaumanni type-series and known for his exhaustive work on the insect fauna of the state of Santa Catarina, Brazil. Plaumann is considered the most important insect collector of Latin America in the 20th century.