Pheidole ragnax, Fischer & Fisher, 2013

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 : 344-346

Pheidole ragnax sp. n.

( Figs. 24A–F )

Holotype: (major worker), MAYOTTE, Reserve Forestiére Sohoa , 12.8059 S, 45.1005 E, 20 m, coastal scrub, rainforest, collection code BLF18941, 29.xi.2007 (B.L. Fisher et al.) ( CASC: CASENT0132467 ).

Paratypes: (5 minor workers) same data as holotype ( CASC: CASENT0136788 – CASENT0136791 ) .

Diagnosis: Comparatively large species (WL major 1.50–1.65 mm, WL minor 1.01–1.07 mm), minor workers with very long scapes and legs (SI 191–209, FI 209–226), major workers with long scapes and legs (SI 64–70, FI 96–108), promesonotal process well developed and in profile subangulate in both worker castes. Major postpetiolar ventral process absent, head about as long as wide (CI 99), frontal carinae and antennal scrobe absent or inconspicuous, head posteriorly wider than anteriorly with slightly oblique sides, eyes relatively large (EI 14– 17), metafemur long (FI 99), metanotal groove in profile broadly impressed, propodeum higher than long and sloped toward spines. Minor head shape elongated (CI 67–75) and with very prominent occipital carina, scapes and legs long (SI 170–209, FI 197–226), eyes large (EI 26–31), anterior half of face superficially punctate, grading to smooth and shiny posteriorly, mesosoma slender and elongated, metanotal groove usually impressed and spines subvertical in profile.

Description of major worker: Measurements (holotype): HW 1.59, HL 1.60, SL 1.12, MDL 0.94, EL 0.26, WL 1.50, PNH 0.63, PNW 0.74, MNH 1.00, PDH 0.47, PTL 0.54, PPL 0.28, PTH 0.29, PPH 0.25, PTW 0.21, PPW 0.56, PSL 0.19, MFL 1.58, MTL 1.19, CI 99, SI 70, MDI 59, EI 16, FI 99, PSLI 12, LPpI 112, DPpI 200, PpWI 267, PpLI 52, PpHI 86.

Head about as long as wide (CI 99), wider posteriorly than anteriorly with oblique sides. Mandibles long (MDI 59), smooth. Clypeus smooth, median carina absent, lateral carinae superficial. Frontal carinae and antennal scrobe absent. Entire face with interrupted longitudinal, posteriorly diverging rugae, rugae at sides of head and posterolateral lobes more irregular with weakly reticulate areas, interspaces weakly to superficially punctate. Scapes relatively long (SI 70), with decumbent to subdecumbent pilosity. Eyes well developed and relatively large (EI 16). Submedian hypostomal teeth and median process very small to inconspicuous. Promesonotum in profile high domed, convex, with a prominent angular posterior process dividing mesonotal declivity into two long, relatively steep slopes, humeri not produced laterally in dorsal view. Surface of promesonotum and lateropronotum superficially punctate with irregular transverse rugulae anteriorly and oblique longitudinal rugulae posteriorly on dorsum of mesonotum, rest of mesosoma weakly sculptured. Metanotal groove broadly impressed in profile, with inconspicuous cross-ribs. Dorsum of propodeum anterior of spines shorter than posterior declivity. Propodeal spines relatively long-spinose, almost as long as distance between their bases (PSI 12). Metatibia long (FI 99), pilosity abundant, coarse, and decumbent to subdecumbent. Dorsum of waist segments smooth to superficially punctate, remainder superficially punctate. Postpetiole in dorsal view very wide, about 2.7 times wider than petiole (PpWI 267), ventral process and lateral process absent. Gaster smooth, anteriorly superficially punctate. Standing hairs abundant, relatively stiff, yellowish, on head and mesosoma short, on postpetiole and gaster longer. Shorter pilosity subdecumbent and abundant. Color light reddish brown, with darker gaster.

Description of minor workers: Measurements (n=5): HW 0.53–0.58 (0.55), HL 0.75–0.80 (0.79), SL 1.05– 1.13 (1.10), MDL 0.41–0.54 (0.45), EL 0.16–0.17 (0.16), WL 1.01–1.07 (1.05), PNH 0.28–0.31 (0.29), PNW 0.36–0.40 (0.38), MNH 0.54–0.66 (0.61), PDH 0.26–0.27 (0.26), PTL 0.31–0.35 (0.33), PPL 0.15–0.21 (0.19), PTH 0.15–0.16 (0.15), PPH 0.10–0.13 (0.11), PTW 0.09–0.10 (0.09), PPW 0.14–0.18 (0.16), PSL 0.07–0.09 (0.07), MFL 1.18–1.22 (1.20), MTL 0.93–0.97 (0.95), CI 67–72 (69), SI 191–209 (202), MDI 76–102 (82), EI 29– 31 (30), FI 209–226 (219), PSLI 13–15 (14), LPpI 150–183 (167), DPpI 76–94 (85), PpWI 156–178 (171), PpLI 48–68 (57), PpHI 67–80 (73).

Head shape elongate ovoid, almost 1.5 times longer than wide (CI 67–72), sides convex and posteriorly converging toward constricted posterior head margin, with occipital carina conspicuously raised to flange-like collar. Mandibles long (MDI 76–80), smooth. Clypeus smooth, median and lateral carinae absent. Face smooth, except for superficial punctures and malar carinae reaching toward posterior eye level. Scapes twice as long as head width (SI 191–209), pilosity subdecumbent to suberect. Eyes large (EI 29–31). Pronotum in profile flatly convex, posterior promesonotal process well developed, prominently produced, and subangulate. Metanotal groove barely to broadly and deeply impressed, with superficial to inconspicuous cross-ribs. Propodeum in profile longer than high, declining smoothly toward spines. Propodeal spines acute, moderately short-spinose, almost vertical, and somewhat shorter than distance between their bases (PSLI 13–15). Promesonotum almost completely smooth, at most with superficial sculpture on mesopleuron and propodeum. Metafemur long (FI 209–226), metatibia with subdecumbent to suberect pilosity. Postpetiole in profile without ventral process, on average 1.7 times longer than high (LPpI 150–183), and significantly lower than petiole (PpHI 67–80). Petiole and postpetiole dorsum smooth, remainder at most superficially sculptured. Gaster smooth and shiny. Standing hairs erect to suberect, short, stiff, and blunt, scarce on mesosoma, shorter pilosity absent. Color light yellow, with gaster and tibiae darker.

Discussion: Pheidole ragnax seems closely related to P. bessonii Forel from Madagascar, as the two share important key characters such as the occipital collar and the elongated shapes of the head, mesonotum, scapes, legs, and postpetiole in minor workers, and the acute lateral postpetiolar process and face with obliquely longitudinal rugae in major workers. All six specimens of this species were collected from a single rotten log in coastal scrub rainforest on Mayotte, which is less than 350 km north and east of the coast of Madagascar. Such proximity suggests that P. ragnax could represent a mere geographic variation of P. bessonii . Nevertheless, the P. ragnax specimens can be clearly separated from the type material of P. bessonii by the more elongated head shape (CI 67– 72 versus CI 76), scapes (SI 191–209 versus SI 176), and legs (FI 209–226 versus FI 198) in the minor workers. The holotype major worker of P. ragnax differs from that of P. bessonii in the oblique versus convex head sides, as well as longer scapes (SI 70 versus SI 59), mandibles (MDI 59 versus MDI 49), legs (FI 99 versus FI 86), and larger eyes (EI 16 versus EI 12). However, until more material of P. ragnax is collected and the whole group is revised, there will not be a definite answer to whether P. ragnax is a synonym of P. bessonii or a distinct biological species.

Etymology: The name of this species is an arbitrary combination of letters.

Figures

FIGURE 24 Pheidole ragnax sp. n., full-face view (A), profile (B), and dorsal view (C) of paratype minor worker (CASENT0132467) and full-face view (D), profile (E), and dorsal view (F) of holotype major worker (CASENT0136791).