Prionopelta xerosilva Overson & Fisher

Overson, Rick & Fisher, Brian L., 2015, Taxonomic revision of the genus Prionopelta (Hymenoptera, Formicidae) in the Malagasy region, ZooKeys 507, pp. 115-150 : 135-137

Taxon classification Plantae Hymenoptera Formicidae

Prionopelta xerosilva Overson & Fisher sp. n. Figs 1A, 2B, D, 12

Type material.

Holotype, pinned worker, MADAGASCAR, Mahajanga, Réserve Forestière Beanka, 50.7 km E Maintirano, 17.88021°S, 44.46877°E, 140 m, tropical dry forest on tsingy, sifted litter (leaf mold, rotten wood), BLF22999, 29.x.2009 (B.L. Fisher et al.) (CASC: CASENT0157254). Paratypes, six pinned workers with same data as holotype (CASC: CASENT0157257; CASENT0157258; CASENT0157260; CASENT0157262; CASENT0157701, CASENT0157702).

Diagnosis.

Prionopelta xerosilva is identifiable from the following combination of characters: cephalic foveae consistently and widely separated by 1-3 foveal diameters, with foveae directly adjacent only extremely rarely, including at the posterolateral corners of the head; metanotal suture strongly visible in dorsal view.

Worker measurements

(N=6). HL 0.43-0.46 (0.45); HW 0.34-0.36 (0.35); SL 0.23-0.25 (0.24); WL 0.45-0.5 (0.48); PetL 0.14-0.15 (0.15); PetW 0.19-0.21 (0.2); T1W 0.31-0.33 (0.32); CI 74.35-81.82 (77.85); PI 126.8-148.18 (138.76); SI 65.51-71.88 (69.77).

Worker description.

Cephalic foveae shallow, large, and most widely spaced of the Malagasy Prionopelta ; directly adjacent cephalic foveae either completely lacking, or very rare; if any foveae are adjacent, then always with only 2-3 foveae connected, and these usually located medially on the head in full-face view; majority of cephalic foveae are separated by 1-3 foveal diameters, appear cleanly scooped from shining integument, and lack any raised margins at their perimeter; median cephalic band devoid of foveae is wide along its length, not tapering posteriorly; coronal suture absent medially on the head; apical tooth intermediate in length, never more than 4 times as long as the third tooth from base to tip (Fig. 2D); very weak, shallow, foveae present on the pronotum which are noticeably less dense than those of other Malagasy Prionopelta ; foveae of the dorsum of the mesosoma interspersed with punctures; pronounced metanotal suture visible in dorsal view, mesopropodeal suture weaker but present; posterior edge of the propodeum straight or only very slightly concave in dorsal view; protruding lamellae of the posterior propodeum absent.

Etymology.

The name of this new species is a combination of the Greek adjective “xero” meaning dry and the Latin noun “silva” for forest, as this species is known only from tropical dry forests in western Madagascar.

Distribution and ecology.

Prionopelta xerosilva is known only from tropical dry forests in the province of Mahajanga in western-central Madagascar (Fig. 13). It has only been collected from forest litter and ranges between 50-300 meters of elevation.

Taxonomic notes.

With its uniformly and widely spaced cephalic foveae, Prionopelta xerosilva could only be confused with Prionopelta vampira . However, the latter lacks a metanotal suture and possesses a very long apical tooth, a strongly concave posterior edge of the propodeum in dorsal view, and lamellae protruding from the posterior propodeum, all of which Prionopelta xerosilva lacks.

Non-type material.

MADAGASCAR: Mahajanga, Parc National Tsingy de Bemaraha, 10.6 km ESE 123° Antsalova, 18.7094°S, 44.7182°E, 150 m, tropical dry forest on Tsingy, 16.xi.2001 (Fisher-Griswold Arthropod Team); Mahajanga, Parc National Tsingy de Bemaraha, 2.5 km 62° ENE Bekopaka, Ankidrodroa River, 19.1322°S, 44.8147°E, 100 m, tropical dry forest on Tsingy, 11.xi.2001 (Fisher-Griswold Arthropod Team); Mahajanga, Parc National Tsingy de Bemaraha, 3.4 km 93° E Bekopaka, Tombeau Vazimba, 19.1419°S, 44.828°E, 50 m, tropical dry forest, 6.xi.2001 (Fisher-Griswold Arthropod Team); Mahajanga, Réserve forestière Beanka, 50.2 km E Maintirano, 18.0265°S, 44.0505°E, 250 m, tropical dry forest on tsingy, 19.x.2009 (B.L.Fisher et al.); Mahajanga, Réserve forestière Beanka, 52.7 km E Maintirano, 18.0622°S, 44.5259°E, 300 m, tropical dry forest on tsingy, 24.x.2009 (B.L.Fisher et al.).