Eurhopalothrix pilulifera Brown & Kempf, 1960

Longino, John T., 2013, A review of the Central American and Caribbean species of the ant genus Eurhopalothrix Brown and Kempf, 1961 (Hymenoptera, Formicidae), with a key to New World species, Zootaxa 3693 (2), pp. 101-151 : 135-136

Eurhopalothrix pilulifera Brown & Kempf, 1960

( Figs 7A , 28 , 35 )

Eurhopalothrix pilulifera Brown & Kempf, 1960: 208 , fig. 38. Holotype worker: Mexico, Tabasco: Chichicastle, 16 Aug 1945, in berlesate (F. Bonet, No. 1108) [MCZC] (not examined). Paratype queen: Brazil, Rio de Janeiro, 18 Mar 1932 (H. Souza Lopes) [MZSP].

Geographic range. Mexico, El Salvador, Honduras, Costa Rica. Uncertain: Brazil (Rio de Janeiro).

Description. Worker. HW 0.53–0.58, HL 0.56–0.64, SL 0.35–0.40, SLL 0.08–0.11, CI 89–97, SLI 21–28 (n=4–5). Labrum anteriorly bilobed, possibly shaped like labrum of E. xibalba ( Fig. 2 G) (based on partial view, specimen with closed mandibles); mandible short, triangular, dorsal surface strongly convex, apical half strongly down-curved, surface punctate, rounding into ventral surface; masticatory margin not observed clearly but partial view shows two tooth rows, an outer row of flattened, triangular teeth and an inner row of several longer needleshaped teeth; scape with very strongly developed basal lobe; scrobe deep, sharply delimited dorsally and ventrally, abutting deep antennal socket; surface of scrobe feebly foveolate; eye minute, comprising 1–3 fused ommatidia; clypeus minutely and shallowly punctate, shallowly convex medially, with shallow circular concavities anterolaterally, cuticle of these concavities transparent, contrasting with surrounding opaque cuticle; sides of head above eyes angulate, vertex margin strongly concave; surface of face uniformly convex, minutely and densely punctate; occipital carina distinct; undersurface of head uniformly punctate; postgenal suture visible as a longitudinal dark line.

Promesonotal profile low, shallowly convex, posterior margin a short step dropping to sloping, flat dorsal face of propodeum; metanotal groove not impressed; dorsal and posterior faces of propodeum distinct, meeting at obtuse angle, dorsal face subequal in length to posterior face; propodeal spine laminar, translucent, in the form of a broad foliaceous lamella, upper margin right-angled, lamella extending down posterior face to propodeal lobe; propodeal spiracle small, directed somewhat posteriorly; entire mesosoma minutely and densely punctate.

Petiolar peduncle joins anterior face of petiolar node at a sharp (not rounded) obtuse angle; anterior face of node meets dorsal face at blunt right to slightly acute angle; posterior face of node short; ventral margin of petiole with large, blunt anteroventral tooth; postpetiole low and broad, with a feeble longitudinal sulcus dorsally; first gastral sternite lacking anterior sagittal keel; petiole, postpetiole, and gaster minutely and densely punctate.

Dorsal surface of scape uniformly covered with broadly spatulate, fully appressed ground pilosity; setae on leading edge of scape similar to dorsal pilosity, fully appressed and not at all projecting; ground pilosity on clypeus obsolete; ground pilosity of face conspicuous, ground setae decumbent, pompon-like, similar in form to the larger specialized projecting setae, but much smaller, about 1/4 the size, uniformly distributed across face (including frontal lobes) or sparser medially, denser peripherally; projecting specialized setae large, strongly pompon-like, full complement 18, with curved anterior row of 8, transverse median row of 4, and posterior row of 6 on vertex margin; dorsal promesonotum, dorsa of petiolar node and postpetiole, and first gastral tergite with ground pilosity similar to face; 3 pairs projecting pompon-like setae on promesonotum; legs with dense, strongly flattened, decumbent setae on apices of femora, posterior face of foretibia, entire midtibia, anterior face of hindtibia, somewhat sparser on other surfaces; setae at apices of tibiae not distinctly larger or differentiated from more proximal setae; basitarsus and remaining tarsomeres with abundant, strongly spatulate setae; two large pomponlike setae on hind margin of dorsal face of petiolar node; row of 4 pompon-like setae on hind margin of postpetiole, median pair only slightly smaller than lateral pair; specialized setae of first gastral tergite pompon-like, full complement about 20, distributed across entire tergite and along posterior margin, medial setae in two longitudinal rows of 5 pairs.

Color orange.

Biology. This is a very rare species, known from 5 specimens from 5 widely-spaced localities. Collections have been in dry forest or second-growth wet forest habitats, all from Berlese or Winkler samples of forest floor litter and rotten wood.

Comments. A distinctive feature that is unique to E. pilulifera , at least among New World species, is an absence of differentiated setae projecting from the anterior margin of the scape. The dorsal surface of the scape is uniformly covered with scale-like, fully appressed setae. These setae also line the anterior edge but do not project on stalks or differ in any other way from those on the dorsal surface. All other species I have examined have projecting setae on the anterior margin. Eurhopalothrix pilulifera is most similar to E. alopeciosa and E. clypeata , sharing the small size; a similar arrangement and number of erect setae, these almost circular, nearly as broad as wide; and abundant ground pilosity that is strongly flattened and conspicuous. It has a simple clypeus, without an arcuate transverse carina (present in E. clypeata ). The propodeal spine is in the form of a rectangular lamella extending down the posterior face of the propodeum (propodeal spine acute in E. alopeciosa , with narrow infradental lamella). Eurhopalothrix pilulifera may also be confused with E. xibalba , which is larger and has thinner ground pilosity.

The holotype differs from the four other examined specimens in being slightly larger and having a relatively more elongate head (CI 89 versus 95–96). Brown and Kempf (1960) described a paratype queen from Rio de Janeiro, Brazil. This record should be considered suspect, pending fuller characterization of the fauna in southern Brazil.

Figures

FIGURE 2. Eurhopalothrix labra. A. E. bolaui (Nicaragua, CASENT 0619922). B. E. semicapillum (Costa Rica, CASENT 0639342). C. E. ortizae (Costa Rica, LACM ENT 143281). D. E. gravis (Costa Rica, INB 0003212299). E. E. sepultura (Mexico, CASENT 0639334). F. E. mabuya (Cuba, CASENT 0630193). G. E. xibalba (Costa Rica, INB 0003698926). H. E. floridana (USA, LACM ENT 143276). I. E. cimu (Cuba, CASENT 0639337). A – H are dissected labra imaged in fluid. I is dry-mounted specimen, basal portion is not visible, and maxilla are visible in background. With the exception of E. cimu, specimen codes are for dry-mounted specimens from the same series, not the dissected specimen. Images are not to scale.

FIGURE 28. Eurhopalothrix pilulifera worker (Honduras, CASENT 0618717). Scale bars: face view = 0.2 mm, lateral view = 0.5 mm.

FIGURE 35. Distribution maps of Eurhopalothrix species, Central American region.

FIGURE 7. A. Eurhopalothrix pilulifera, showing expanded infradental lamella. B. E. xibalba, showing narrow infradental lamella.