Strumigenys dahlanae

The type material was collected from leaf litter in primary forest.

Identification
Sosa-Calvo et al. (2010) - Very small (TL = 1.38–1.42); eyes absent; mandibles linear, elongate, and in closed position with gap between basal mandibular teeth and anterior portion of clypeus; propodeum unarmed; ventral portion of petiole lacking spongiform tissue.

Strumigenys dahlanae is most similar to members of the Nearctic pergandei-group, which includes Strumigenys angulata, known from the southeastern United States and Illinois, and Strumigenys pergandei (Emery), widely distributed in Canada and the United States. Strumigenys dahlanae shares with those species the following characters: (i) mandibles short (MI 25–35) and, in frontal view, narrow and elongate, dentate only at the apical portion where they are in contact leaving an edentate gap between them; (ii) specialized mandibular dentition (alternating pattern of longer and shorter mandibular teeth); (iii) lateral clypeal margins, in dorsal view, extending beyond the line of the outer margin of the mandibles when closed; and (iv) preocular carina broad and conspicuous. Strumigenys dahlanae differs from the species in the pergandei-group in four character states: (i) 10 mandibular teeth (15–16 in the pergandei-group), (ii) absence of triangular teeth on the propodeum (present in the pergandei-group), (iii) absence of a well-developed spongiform tissue on the ventral portion of the petiole (present in the pergandei-group), and (iv) shorter antennal scape, SI 57–59 (SI 65–84 in the pergandei-group).

The mandibles of S. dahlanae are similar to those within the pergandei-group in that they contact in the apical third, producing a basal gap between the mandibles. This condition is different from the one found in species in the ohioensis-group, in which the masticatory margins contact through almost their entire lengths and in which the mandibles are triangular rather than elongate. Elongate mandibles can be found in the gundlachi- and argiola-groups, the latter an Old World group introduced into the United States (Strumigenys hexamera). Mandibles in S. hexamera are highly distinctive with an elongate and spiniform apicodorsal tooth and two long preapical teeth (see Bolton 2000 for further information). Species of the gundlachi-group share with S. dahlanae the absence of a spongiform lobe on the ventral surface of the petiole but differ from S. dahlanae in: (i) mandibular length and morphology, (ii) the presence of a pair of triangular teeth or short spines on the propodeum, and (iii) the presence of pronotal humeral hairs and, in almost all species, a pair of laterally projecting apicoscrobal hairs.

Strumigenys dahlanae may also be related to Strumigenys paradoxa Bolton, known from a single worker collected in Costa Rica. Both species share the absence of propodeal spines; however, S. dahlanae differs from S. paradoxa by the shape of the mandibles, and the head and mesosoma strongly areolate with the meso- and metapleuron smooth and shining. The head and mesosoma are mostly smooth and shining in S. paradoxa. Although S. dahlanae shares a number of character states with some members of the aforementioned groups, this species is not easily placed in any of the species groups defined by Bolton (2000).

Distribution based on Regional Taxon Lists
Neotropical Region: Guyana.

Castes
Known only from the worker caste.

Nomenclature

 *  dahlanae. Pyramica dahlanae Sosa-Calso, Schultz & LaPolla, 2010: 15, figs. 1-5 (w.) GUYANA. Combination in Strumigenys: unpublished.

Worker
Holotype (and paratype): GL=0.3 (0.32), HL=0.34, HW=0.27 (0.28), ML=0.09, PL=0.17, PPL=0.12 (0.11), PW=0.19 (0.18), SL=0.16, TL=1.42 (1.38), WL=0.39 (0.36). Indexes: CI=82 (79), MI=26, PI=47 (44), SI=59 (57). (n=2)

Head: in full-face view, clypeus slightly concave anteriorly, with long apical spoon-shaped hairs extending over mandibular gap; mandibles sublinear and elongate; at full closure mandibles contacting only in apical halves of their lengths, leaving gap between them basally; mandibles with 10 teeth, basal tooth acute, all other teeth rounded and flattened; teeth 1, 3, 5, 7, 9, and 10 (from base to apex) larger than other teeth; lateral dorsum of mandible with appressed simple hairs; eyes absent; sculpture on clypeal plate imbricate; sculpture on cephalic dorsum areolate and covered with squamate hairs; hairs on anterior margin (leading edge) of scape spoon-shaped and directed basad; antennal scape narrowed basally, anterior margin abruptly expanded, distinctly widest at point of expansion; apicoscrobal hair absent. Mesosoma: dorsum of anterior portion of pronotum glabrous; pronotal humeral hair absent; dorsum of promesonotum and dorsum and declivity of propodeum entirely areolate; propodeum lacking spines or denticles at its posterior margin; mesopleuron and metapleuron smooth and shining; dorsal portion of mesosoma covered with appressed spoon-shaped hairs (as on head) without erect hairs of any kind, lateral portions glabrous. Metasoma: petiole lacking ventral spongiform lobe, petiolar disc areolate and covered with slightly appressed spatulate hairs; lateral surface of petiolar peduncle smooth and shining; ventral surface of side of petiole weakly sculptured; disc of postpetiole weakly sculptured and shining, covered with hairs similar to those on petiole but narrower; ventral surface of postpetiole with well-developed spongiform lobe that extends throughout its entire length; lateral spongiform tissue overhanging ventral spongiform lobe; dorsal surface of first gastral segment smooth with some longitudinal basigastral costulae. Color: individuals light yellow to dark yellow. Hairs throughout body lighter than integument.

Type Material
Holotype: worker, labeled: ‘‘GUYANA: Mabura Hill camp at end of Rd. from Georgetown to Lethem Rd.; 64 m; 58u 41.9829 W 5u 9.3139 N; 29 x 2002; J.S. LaPolla et al.; primary forest; litter sample. (JSL021029-LS04)’’ USNM ENT No. 00442119.

Paratype: worker, labeled: ‘‘GUYANA: Calm Water Creek along Essequibo River nr. Bartica; 58u 37.169 W 6u 28.069 N; 23 ix 2002; J. S. LaPolla; primary forest; litter sample. (JSL020923-LS02)’’ USNM ENT No. 00441577.

Etymology
Named after Ms. Nor Faridah Dahlan in recognition of her expertise and hard work in support of Smithsonian ant research and in gratitude for her consistent good will and friendship. JS-C is deeply grateful to Faridah for all her help and care when he first arrived in the United States.

References based on Global Ant Biodiversity Informatics

 * Sosa-Calvo J., T. R. Schultz, and J. S. LaPolla. 2010. A review of the dacetine ants of Guyana (Formicidae: Myrmicinae). Journal of Hymenoptera Research 19: 12-43.