Pheidole braueri Forel

FISCHER, G. & FISHER, B. L., 2013, A revision of Pheidole Westwood (Hymenoptera: Formicidae) in the islands of the Southwest Indian Ocean and designation of a neotype for the invasive Pheidole megacephala, Zootaxa 3683 (4), pp. 301-356 : 314-316

Pheidole braueri Forel

( Figs. 14A–F )

Pheidole braueri Forel, 1897: 204 .

Lectotype (major worker, CASENT0101604 ) [designated here]: SEYCHELLES (A. Brauer) ( MHNG) [examined] ; paralectotypes (1 major worker & 3 minor workers, CASENT0101604 & CASENT0101571 ) same data as lectotype ( MHNG) [examined].

Diagnosis: Relatively small species (WL major 0.81–0.85 mm, WL minor 0.51–0.56 mm), with short scapes and legs (SI major 41–51, FI major 51–56; SI minor 91–98, FI minor 93–100); both worker castes with promesonotal process absent. Major head rectangular, longer than wide, frontal carinae strongly divergent posteriorly, extending to about 3/5 of the way to the posterior head margin, scrobe well defined, in lateral view a very shallow depression posterior of frontal carinae, hypostomal margin with large submedian teeth, median process absent, spines relatively long (PSLI 15–16), postpetiole higher than long (LPpI 80–89), with small acute ventral process. Minor head subrectangular, face smooth to weakly punctate, posterior head margin slightly concave, scapes short (SI 91–98), scape pilosity mostly suberect with few longer erect hairs along outer edge, pronotum largely smooth, rest of mesonotum weakly to superficially punctate, propodeal spines slightly shorter than distance between their bases (PSLI 18–22), postpetiole without ventral process and on average as long as high (LPpI 94–110).

Description of major workers: Measurements (lectotype): HW 1.07, HL 1.15, SL 0.47, MDL 0.55, EL 0.15, WL 0.84, PNH 0.48, PNW 0.55, MNH 0.57, PDH 0.31, PTL 0.33, PPL 0.16, PTH 0.22, PPH 0.20, PTW 0.15, PPW 0.25, PSL 0.17, MFL 0.58, MTL 0.41, CI 93, SI 44, MDI 51, EI 14, FI 54, PSLI 15, LPpI 80, DPpI 153, PpWI 163, PpLI 48, PpHI 91.

Measurements (n=5): HW 1.05–1.13 (1.08), HL 1.13–1.19 (1.17), SL 0.45–0.55 (0.48), MDL 0.53–0.56 (0.55), EL 0.13–0.15 (0.14), WL 0.81–0.85 (0.83), PNH 0.43–0.47 (0.45), PNW 0.58–0.61 (0.59), MNH 0.60–0.64 (0.62), PDH 0.30–0.31 (0.30), PTL 0.31–0.33 (0.33), PPL 0.16–0.17 (0.16), PTH 0.20–0.21 (0.21), PPH 0.19–0.20 (0.19), PTW 0.15–0.17 (0.16), PPW 0.23–0.26 (0.24), PSL 0.16–0.18 (0.17), MFL 0.57–0.59 (0.58), MTL 0.40– 0.42 (0.41), CI 90–96 (93), SI 41–51 (45), MDI 47–53 (51), EI 12–14 (13), FI 51–56 (54), PSLI 15–16 (15), LPpI 80–89 (85), DPpI 141–156 (147), PpWI 135–167 (152), PpLI 48–52 (50), PpHI 90–95 (93).

Head slightly longer than wide (CI 90–96), rectangular with almost parallel sides and deep, broadly V–shaped posterior emargination. Mandibles smooth and shiny, compact, and relatively short (MDI 47–53). Clypeus smooth, with median carina absent, and lateral carinae short. Frons longitudinally rugose, with short irregular rugae between longer rugae, on posterior half of head grading into coarsely reticulate sculpture, spaces between rugae smooth to superficially punctate. Frontal carinae reaching slightly behind head midlength, strongly developed, laterally extended, and curving over well developed, smooth to superficially punctate antennal scrobe. Sides of head anterior of scrobes densely rugose-punctate. Scapes relatively short (SI 41–51) and strongly arcuate, with decumbent pilosity and few long, erect standing hairs on outer edge. In profile, head anterior of posterolateral lobes with a faintly concave depression. Head posteriorly and lateroventrally, in dorsal and in profile view, mostly smooth and shiny, almost entirely without sculpture. Submedian hypostomal teeth large, median process absent. Promesonotal dome strongly developed and convex in profile, promesonotal process absent, posterior declivity weakly angulate, in dorsal view wide with humeri distinctly laterally produced. Surface of promesonotum and lateropronotum partly smooth or micropunctate, partly superficially punctate, dorsally with some or several irregular longitudinal or transverse rugae, katepisternum with large smooth area, remainder of mesosoma faintly to superficially punctate. Metanotal groove narrow, barely or not impressed, and with weakly developed cross-ribs. Propodeal spines comparatively stout and long (PSLI 15–16). Metafemur very short (FI 51–56), metatibia with decumbent pilosity. Postpetiole in profile higher than long (LPpI 80–89), with small, weakly angulate to anteriorly acute ventral process, in dorsal view anteriorly wider than posteriorly, and on average 1.5 times wider than petiole (PpWI 135–167). Petiole and postpetiole smooth to superficially punctate. Gaster smooth. Several short to moderately long, stiff standing hairs on dorsal head and body, pilosity short and decumbent. Color reddish brown, with lighter legs and darker gaster.

Description of minor workers: Measurements (n=5): HW 0.42–0.45 (0.44), HL 0.45–0.47 (0.46), SL 0.41– 0.42 (0.41), MDL 0.27–0.30 (0.29), EL 0.10–0.11 (0.11), WL 0.51–0.56 (0.54), PNH 0.19–0.22 (0.21), PNW 0.29– 0.34 (0.31), MNH 0.35–0.43 (0.38), PDH 0.18–0.22 (0.20), PTL 0.18–0.23 (0.20), PPL 0.09–0.11 (0.10), PTH 0.12–0.14 (0.13), PPH 0.10–0.12 (0.10), PTW 0.08–0.10 (0.08), PPW 0.12–0.15 (0.13), PSL 0.07–0.10 (0.08), MFL 0.40–0.47 (0.43), MTL 0.29–0.35 (0.32), CI 80–95 (91), SI 85–103 (89), MDI 61–74 (66), EI 20–24 (22), FI 91–108 (95), PSLI 15–21 (18), LPpI 39–41 (40), DPpI 109–141 (122), PpWI 141–160 (152), PpLI 47–58 (53), PpHI 79–91 (85).

Head subquadrate, slightly longer than wide (CI 91–98), sides strongly convex, posterior head margin slightly concave, occipital carina not visible in full-face view. Mandibles relatively short (MDI 62–70), smooth. Clypeus smooth or superficially punctate, median carina absent to inconspicuous, lateral carinae weak and irregular. Face sculpture varying from uniformly smooth and shiny in some specimens medially smooth or superficially punctate with weak to superficial punctures and laterally overlain with few faint rugulae. Scapes short (SI 91–98), when laid back in full-face view barely reaching beyond posterior head margin, pilosity mostly suberect, few hairs along outer edge longer and erect. Eyes moderately large (EI 20–24), oval, and anteriorly narrower. Promesonotal outline in lateral view flatly convex with promesonotum extended posteriorly, weakly subangulate at posterior declivity. Metanotal groove in profile shallowly impressed, with weak cross-ribs, the two lateromedian cross-ribs sometimes continued as faintly developed rugulae along dorsolateral propodeal margins, ending at propodeal spines. Pronotum smooth with areas of weak to superficial punctures anteriorly, posteriorly, and laterally, mesonotum and propodeum weakly to superficially punctate with smooth areas dorsally and laterally. Propodeal spines acute, short-spinose, slightly shorter than distance between their bases (PSLI 18–22). Metafemur short (FI 93–100), metatibia with subdecumbent pilosity and scattered suberect hairs. Postpetiole on average slightly longer than high (LPpI 94–110), without ventral process, petiole and postpetiole surface usually smooth. Gaster smooth and shiny. Standing hairs short, stiff, and suberect, a few longer erect hairs present on dorsum of head and promesonotum. Color yellow to orange with darker gaster.

Discussion: Pheidole braueri was described from specimens collected by August Bernhard Brauer who collected insects on Mahé and Silhouette islands, so the precise locality of the type series is unknown. However, subsequent collections are only from Silhouette Island. Thus, this species may be restricted to Silhouette Island. Based on similarities in external morphology, especially the head and body of the major worker, P. braueri seems to belong to a widespread group of morphologically related species. The geographic distribution of this potentially monophyletic species group ranges from the Seychelles in the Southwest Indian Ocean to Borneo and to several smaller islands in Micronesia and Melanesia in the South and West Pacific Ocean. This group contains several species with majors that resemble those of P. braueri in key characters including head morphology and the shape of the mesosoma and waist segments. Possibly related species are Pheidole philemon Forel ( Solomon Islands), P. hortensis Forel (Borneo and Indonesia), P. maculifrons Wheeler ( Philippines) , P. recondita Clouse ( Guam) , P. fantasia Chapman ( Philippines) , P. clypeocornis Eguchi , P. kikutai Eguchi , P. retivertex Eguchi , P. rugifera Eguchi , P. sayapensis Eguchi , (these last five from Borneo see Eguchi 2001), and P. tjibodana Forel (Southeast Asia). Intraspecifically P. braueri minor workers display a significant amount of variability in face and mesosoma sculpture. In contrast to a largely weak to superficial punctate sculpture in most specimens, the heads and mesosomas of the type material are almost entirely smooth and shiny. Despite these relatively distinct intraspecific differences, the morphology and measurements of the types, especially of the major workers, are identical to those of the more recently collected material. Within the Malagasy region, P. braueri is a unique species recognizable by the features listed in its diagnosis.

A lectotype major worker, plus a paralectotype major and three paralectotypes minor workers, are herewith designated from the syntype series. One major worker (CASENT0104598) from the syntype series is morphologically different from the rest of the series and is excluded from the paralectotypes. It differs from all other material examined for this work and most likely represents a different species. We defer identification until more is known about this distinctive specimen.

Additional material examined: SEYCHELLES: Silhouette Island: Corgat-Cocos Marron Ridge, 18.vii.2000 (J. Gerlach); ridge from Mont Corgat to Mont Cocos Marrons , 4.50126 S, 55.2398 E, 455 m, forest, 24.i.2010 (B.L. Fisher et al.); on ridge toward Mont Corgat, 4.49537 S, 55.2395 E, 445 m, forest, 25.i.2010 / 28.i.2010 (B.L. Fisher et al.) .

Figures

FIGURE 14 Pheidole braueri Forel, full-face view (A), profile (B), and dorsal view (C) of minor worker (CASENT0159919) and full-face view (D), profile (E), and dorsal view (F) of major worker (CASENT0217235).