Prionopelta descarpentriesi

Identification
Overson and Fisher (2015) - P. descarpentriesi can be identified by the following combination of characters: twelve antennal segments; median cephalic band lacking a thin suture that is swollen above the surrounding integument; placement of cephalic foveae ranging from sparse to dense, but always at minimum, with at least several clusters of foveae directly adjacent to one another (if nowhere else, then medially in full-face view); if all foveae on the head are directly adjacent so that no flat, shining space is present between foveae, then foveae are large and accompanied by pronotal sculpture which is characterized as being both similar in size to that on the head and not consisting of smaller foveae or punctures; eye appearing as either an asymmetrical dark patch which appears to be a stain in the cuticle that is flush with its surrounding integument, or a single, slightly rounded glob with no definable subunits.

Three generalized morphotypes can be distinguished within this taxon; these vary in density of cephalic foveae and other co-occurring traits (Fig. 6). In morphotype A, the majority of foveae are equidistantly spaced and separated by a span of shining integument of around one foveal diameter (Figs 1C, 5A, 6A). These foveae appear cleanly scooped from the surface of the integument and largely lack raised margins. Morphotype B, which is intermediate between A and C, has denser cephalic foveae covering almost the entire head, however foveae are smaller and more delicate than those of morphotype C and raised ridges between foveae are less pronounced (Fig. 6B). Pronotal sculpture in morphotype B usually consists of several sizes of foveae along with some punctures. Morphotype C possesses large, dense cephalic foveae that cover the entire head, accompanied by a pronounced network of raised, jagged ridges between foveae (Figs 1D, 3D, 4C, 6C). Morphotype C additionally has large, deep, and evenly spaced pronotal foveae that are similar in size to those on the head, and this morphotype lacks smaller foveae or punctures on the pronotum. Width of the median cephalic band devoid of foveae is widest in morphotype A and narrowest in morphotype C.

P. descarpentriesi is much more morphologically variable than the other species treated in this revision and very possibly represents a species complex. This could explain why P. descarpentriesi is abundant, geographically widespread, and morphologically variable. Morphotype C, which is restricted to a band bordering the coast of eastern and northern Madagascar (Fig. 14), is recognizably distinct from the majority of individuals from interior populations of the species. At several localities where morphotype C is present, individuals from morphotype A and B are also present with little to no evidence of character blending between morphotypes: Galako, Makirovana, Morojejy Nature Reserve, and Sahafina. However, at other locales such as Ambohijanahary, Montagne d’Ambre, and Vohemar, a bewildering array of intermediate forms have been collected, blurring the lines between the three morphotypes. Collecting nest series from the aforementioned locations to determine whether this population-level variation is intra- or intercolonial is an important first step in ultimately understanding how morphological variation is partioned in this taxon as currently dilineated.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  descarpentriesi. Prionopelta descarpentriesi Santschi, 1924b: 195 (w.) MADAGASCAR.

Worker
Overson and Fisher (2015) - (N=25). HL 0.42–0.53 (0.48); HW 0.32–0.43 (0.38); SL 0.22–0.3 (0.26); WL 0.46–0.6 (0.52); PetL 0.11–0.2 (0.16); PetW 0.17–0.26 (0.22); T1W 0.29–0.37 (0.33); CI 74.64–85.1 (79.6); PI 118.23–173.29 (141.94); SI 61.46–72.38 (67.31).

Posterior margin of the head straight to weakly concave in full-face view; spacing of cephalic foveae highly variable, ranging from individuals with dense, directly adjacent foveae covering the entire head (known only from far eastern and northern Madagascar, see morphotype descriptions below), to individuals with foveae more widely spaced so that shining areas are visible between; median cephalic band devoid of foveae ranging from wide to extremely narrow but never appearing as a linear suture that is uniformly swollen above the level of the surrounding integument; apical tooth intermediate in length; evenly-space pronotal foveae range from shallow to deep; shallow foveae present on mesonotum and propodeum.

Type Material
Overson and Fisher (2015) - Lectotype, pinned worker, CASENT0101548 [designated here], MADAGASCAR, Ikelivia, 30.ix.1923 (Descarpentries) [examined]. Paralectotypes, one pinned worker CASENT0101547 with same data as lectotype (NHMB) [examined].

Under the above scheme, the lectotype and paralectotype of P. descarpentriesi would be considered morphotype A. Jules Descarpentries (1881–1927) collected the types for this species on 30 September 1923 and the collection locale was subsequently noted as “Ikelivia”, making it difficult to determine a more precise location based on modern place names. Historical records indicate that Descarpentries resided in Tulear, and worked as a topographic surveyor and entomologist. According to records, he was active around Tsaratanana and Fianarantsoa (specifically Andringitra) and often traveled with H. Perrier de la Bâthie. Given that morphotype A is reasonably widespread across Madagascar, including Tsaratanana and Andringitra, it is possible that the type specimens from “Ikelivia” were collected in either of these localities. To further complicate matters, most of Descarpentries’s specimens, which were destined to the Paris Museum, were sold on the side by a member of the staff. Before the specimens were sold, the labels were changed to hide their true ordinance (Jeannel 1951, (Anonymous 1970)).