Strumigenys convexiceps, Santschi 1931

Booher, Douglas B., Prebus, Matthew & Lubertazzi, David, 2019, A taxonomic revision of the Strumigenys nitens and simulans groups (Hymenoptera: Formicidae), two Caribbean radiations of leaf litter ants, Zootaxa 4656 (2), pp. 335-358 : 340-342

Strumigenys convexiceps, Santschi 1931

( Fig. 3 )

Strumigenys (Codiomyrmex) convexiceps Santschi 1931: 277 , figs. 9, 10. Syntype workers, CUBA: Havana, Playa Marianao, 27.iv.1930, A. Bierig (CASENT0912830) [NHMB]. Images examined on www.antweb.org.

Codiomyrmex convexiceps Santschi : Weber 1934: 52. First combination in Codiomyrmex .

Glamyromyrmex convexiceps Santschi : Brown 1948: 116. First combination in Glamyromyrmex .

Pyramica convexiceps Santschi : Bolton 1999: 1672. First combination in Pyramica .

Pyramica convexiceps Santschi : Bolton 2000: 208, fig. 143. Redescription of syntype worker.

Strumigenys convexiceps Santschi : Baroni Urbani & de Andrade 2007: 177. Combination reinstated.

Non-type material examined: CUBA: Holguín: 6km S Yamanigüey , 20 33 N, 74 44 W, 25m, 23.viii.2001, P. S. Ward #14437-7, sifted litter (leaf mold, rotten wood), pine forest, 2 workers mounted on same pin (CASENT0914683) [ PSWC] .

Diagnosis. This species can be distinguished from all other nitens group species by the abundance and length of basigastral costulae. In S. convexiceps the basigastral costulae are longer (extending beyond the basal third of tergite vs. limited to the basal fifth of tergite) and more abundant (> 30 in vs. <20). This species is most closely related to S. zemi , but is distinguished by mandibular tooth count of 8–9 vs. 7 in S. zemi , pilosity (adpressed setae on clypeal dorsum and antennal scape in in S. zemi and adpressed in S. convexiceps , and shape of basal three mandibular teeth (spiniform in S. zemi and triangular in S. convexiceps ). Strumigenys convexiceps is distinguished from S. hubbewatyorum , S. nitens and S. caiman in having shorter relative scapes (SI = 47–49 vs. 56–74); and relatively broad petiole (3.0–3.1 times wider vs. <1.3 times wider than long).

Holotype worker measurements (taken from imaged specimen). HL = 0.33; HW = 0.40; ML = 0.11; PW = 0.22; SL = 0.16; FL = 0.25; HT = 0.27; EL = 0.02; TL = 1.62; WL = 0.38; CI = 82; MI = 29; SI = 49.

Non-type worker measurements (n=2). HL = 0.41–0.42 (0.42); HW = 0.34 (0.34); ML = 0.10 (0.10); PW = 0.22–0.23 (0.23); SL = 0.16–0.16 (0.16); FL = 0.23–0.24 (0.23); HT = 0.26–0.26 (0.26); EL = 0.02–0.03 (0.03); TL = 1.63–1.65 (1.64); WL = 0.39 (0.39); CI = 82; MI = 23–24 (24); SI = 47–48 (48)

Worker description. Adapted from the description of Pyramica convexiceps in Bolton (2000) . Mandibles in full face view and at full closure triangular, evenly and strongly convex in profile beyond the anterior clypeal margin; MI 23–24. Mandibles with 6 enlarged teeth basally + 2–3 denticles apically for a tooth count of 8–9. The mandibles with a small basal triangular tooth followed by two larger triangular teeth that do not meet, or barely meet when mandibles are closed. Tooth four, five, and six are spiniform with tooth five being the longest and followed by two to three smaller crowded denticles at the apex. The basal tooth is much smaller than teeth two and three. If a third denticle is present, it is located just apical of tooth six and is much smaller than following two denticles.

In full face view lateral margins of head narrowing slightly from apicoscrobal seta position to insertion of mandibles with a small concave impression between clypeus and frontal lobes. Antennal scapes short (SI = 47–49). Eye small, having 3–4 ommatidia and narrower than greatest thickness of scape (EL = 0.02–0.03 vs. scape thickness 0.05).

Antennal scapes with simple adpressed pilosity directed toward the apex. Clypeal dorsum with sparse, minute, simple adpressed setae directed anteriorly toward midline of head. Dorsum of head with weakly flattened short adpressed setae that are as long, or slightly longer than the space that separates them at their bases. Frontal triangle and area directly posterior to the frontal triangle smooth and shining and bearing minute simple to slightly expanded adpressed setae smaller than those on posterior dorsum of head. Scrobal margins with at least one pair of laterally projecting simple to slightly expanded setae in apicoscrobal positions. Vertex of head with 1–2 pairs of similar erect setae and posterior margin with 2–3 pairs of similar erect setae.

Mesosoma short, 1.7 times the length of the pronotal width. Pronotal humeral setae present, stiff and fine to slightly expanded. Sculpture smooth and shining on dorsum and sides of mesonotum. Anterior pronotal dorsum with a pair of erect setae. Mesonotal and propodeal dorsum with 2–3 pairs similar erect setae present. Sparse, adpressed, minute pilosity on dorsum of mesonotum.

Petiole width at least three times as wide as long. Postpetiole greatly expanded, as wide as pronotum and 2.3–2.5 times as wide as long. Petiolar and postpetiolar disc smooth and shining with 2–3 pairs of erect elongate simple setae.

First gastral tergite with numerous fine basal costulae that extend further than 1/3 the length of the sclerite. Erect setae on gaster present and similar to those on mesonotum as two to four rows in four columns (see taxonomic notes).

Distribution and ecology. Known from only two collections from the island of Cuba. The conditions under which the syntype specimens were collected are unknown, but Playa de Marianao has the climate of a typical subtropical dry forest, with a pronounced dry season from November to April ( Bulto et al. 2006). The non-type specimens were collected via Winkler sifting in low elevation coastal pine forest on the extreme eastern side of the island. This area of the island has no pronounced dry season and is subject to continuous precipitation throughout the year.

Taxonomic notes. Bolton (2000) does not provide morphological measurements for S. convexiceps and provides only the MI provided by Santschi (1931) in his original description. We examined images and estimated measurements of a syntype specimen on antweb.org in order to compare it with other members of the nitens group and our non-type S. convexiceps specimens. We found that the syntype differed from the non-type specimens in the following characters: the syntype lacked apparent anterior erect setae along the scrobal margin, and only bears rows of erect setae on the anterior and posterior margins of first gastral tergite. Because erect setae are easily abraded and otherwise the holotype matches the non-type workers examined here, we consider non-type and type specimens are representative of S. convexiceps .

Figures

FIGURE 3. Worker of Strumigenys convexiceps (CASENT0914683; photographer Zach Lieberman): a) dorsal view b) profile view c) full-face view. Scale bars 0.2 mm.