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Head broader than long (CI 1.25-1.37), with large convex eyes that occupy the anterior two-fifths to one half of the sides of head (REL 0.43-0.57) (Figure 2); mandibles slender, elongate-triangular to sublinear, masticatory margin edentate and weakly differentiated from the unarmed basal margin; external margin of mandible curved basally, straight medially, and bent slightly mesad at apex (Figures 2, 4-5); mandible tips crossing at closure, mandible length subequal to eye length (ML/EL 0.88-1.10, ML/HW 0.35-0.41); genal teeth and hypostomal teeth lacking; clypeus short and transverse, bordered anteriorly by a thin clypeal lamella (apron); antennal sockets horizontal and exposed, and located close to the anterior clypeal margin; antenna 13-segmented, each segment longer than wide; scape of moderate length, SI 0.27-0.31; scape length subequal to or less than the length of ultimate antennal segment (SL/LA13 0.73-0.97), scape length 0.11-0.14* total length of antenna, less than twice the length of the second antennal segment (SL/LA2 1.50-1.78), and slightly more than half the combined length of the second, third and fourth antennal segments (SL/(LA2+LA3+LA4) 0.52-0.65); lateral ocelli separated from median ocellus by about their diameters.
Mesosoma with distinctive pronotum (Figure 3): U-shaped in dorsal view and reduced anteromedially to a thin horizontal strip, set well below the level of the dorsally protruding mesonotum; pronotum triangular in profile, with pointed posterior apex directed towards the wing base; mesonotum lacking notauli; parapsidal sutures very weakly impressed, barely discernable; axillae not meeting medially, connected by a narrow furrow; tegula very small and inconspicuous; mesopleuron lacking oblique transverse sulcus and hence not divided into anepisternum and katepisternum; mesoscutellum prominently bulging, as seen in lateral view; metapleural gland reduced and inconspicuous; propodeal spiracle small, circular, positioned at about midheight of propodeum and slightly posterior to the metanotum. Legs slender (LHT/HL ~1.2); mesotibia and metatibia each with a single short spur; tarsal claws lacking preapical tooth.
Wings with reduced venation (Figure 6); pterostigma present; forewing with elongate submarginal cell, four times longer than wide, and longer than basal cell; base of Rs weak, and absent in one species (Amyrmex BR02), resulting in confluence of the basal and submarginal cells; submarginal cell extending distad of stigma and terminating in an acute point; no free M vein after Rs+M; discal (medial) cell lacking, i.e., m-cu crossvein absent; A merging into cu-a, which curves anteriorly to join M+Cu at the point where veins M and Cu diverge, hence no free A vein distal to cu-a (Figure 6); hindwing lacking closed cells; anterior margin of hindwing with 1-4 hamuli; jugal lobe absent.
Metasoma slender in profile, obovate in dorsal view, widest at abdominal segment 5; abdominal segment 2 (petiole) subquadrate in profile (Figure 3), longer than high or wide, and only weakly constricted posteriorly, the helcium thus apparently quite broad; spiracle on abdominal segment 2 located on anterior third, near anterodorsal extremity; abdominal segment 3 larger than petiole, and not developed as postpetiole nor separated from abdominal segment 4 by a marked constriction; abdominal spiracle 3 located on anterior third of tergite; abdominal segments 2 and 3 with tergosternal fusion; abdominal segment 4 lacking tergosternal fusion; segment 4 with short but distinctly differentiated presclerites; spiracle present on anterior half of tergite 4; abdominal segments 5 and 6 lacking well differentiated presclerites, and not separated from succeeding segments by constrictions; abdominal spiracles 5 and 6 not discernable in specimens examined but possibly present at anterior margins of respective tergites; abdominal tergite 8 (pygidium) small and simple but visible dorsally, not wholly covered by abdominal tergite 7; cerci absent; subgenital plate (abdominal sternite 9) with posterior margin broadly concave but not bifurcate; basal ring not hypertrophied; paramere small and slender with rounded apex, paramere about 0.8* petiole length; volsella a simple, elongate-triangular lobe, lacking differentiated cuspis.
Body size very small; total length, excluding appendages, approximately 1.1-1.7 mm; HW 0.32-0.41, LHT 0.29-0.39; integument mostly smooth and shiny, with scattered piligerous punctures; pilosity common on most of body, suberect to decumbent. Color: body yellowish-brown to medium-brown, head and posterior margins of abdominal segments 4-7 darker, appendages (antennae, mandibles, legs) lighter.
FIGURES 2-5. Automontage images of Amyrmex males. 2. Amyrmex BR01 (CASENT0106184), dorsal (full-face) view of head; 3. Amyrmex BR01 (CASENT0106184), lateral view of body; 4. Amyrmex BR01 (CASENT0106184), close-up of right mandible; 5. Amyrmex golbachiHNS (CASENT0106195), close-up of right mandible.
FIGURE 6. Right forewing, male Amyrmex BR01 (CASENT0106185). The above description is a composite, based on the following material:
Amyrmex BR01, 4 males, BRAZIL Rondonia: Fazenda Rancho Grande, 62km S Ariquemes, 165m, 12-22 November 1991, 10°18' S, 62°53'W, E. M. Fisher (CASC, MZSP, UCDC) (CASENT0106161, CASENT0106183, CASENT0106184, CASENT0106185).
Amyrmex BR02, 1 male, BRAZIL Rondonia: Fazenda Rancho Grande, 62km S Ariquemes, 165m, 12-22 November 1991, 10°18' S, 62°53'W, E. M. Fisher (UCDC) (CASENT0106186).
The male of Amyrmex golbachiHNS from Argentina (Formosa) matches the original description (Kusnezov 1953) and the images of A. golbachiHNS males from Tucuman on AntWeb (www.antweb.org). Differences between the three taxa are summarized in Table 1.
TABLE 1. Differences among males of three species of Amyrmex. Contrasts in mandible shape are depicted in Figures 4-5. "B" and "SM" refer to the basal cell and submarginal cell, respectively.
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