Aenictus carolianus

The type locality lies on Cebu Island within the municipality of Cebu City, at barangay Tabunan, sitio Cantipla-I [= Cantipla-Uno], at an elevation of ca. 800 - 900 m a.s.l. (10°24’ N, 123°49’ E measured in the field by GPS). The habitat is a degraded forest in a water shed area. Specimens were collected in the vicinity of a streamlet. Recently, several new ant species were discovered in this area (Zettel 2007, Zettel and Sorger 2010, Sorger and Zettel, in prep.), which is one of the last natural forests on Cebu Island. (Zettel & Sorger 2010)

Identification
A member of the pachycerus group.

Zettel & Sorger (2010) - Head without “Typhlatta spots”. HW 0.59 - 0.64 mm. Occiput without constriction (“collar”), but with well developed ridge. Parafrontal ridge ca. 0.3 mm long. Anterior clypeal margin convex, without teeth. Mandible broad, with ca. 5 minute denticles. Antenna 10-segmented. Head and pronotum with long setae. Pronotal humeri unarmed. Mesonotum not demarcated from mesopleuron. Dorsal outline of mesosoma almost straight. Dorsal face of propodeum posteriorly down-curved, separated from posterior face by distinct ridge. Petiole elongate, without subpetiolar process.

Aenictus carolianus keys out at couplet 37 in the key by Wilson (1964), but it is very similar to Aenictus reyesi from Negros island. Compared with this species, A. carolianus is much smaller (HW 0.59-0.64 in A. carolianus vs. 0.73-0.74 mm in A. reyesi; fide Chapman 1963 and Wilson 1964), has much longer pilosity on head and mesosoma (PHL 0.22-0.27 mm in A. carolianus vs. 0.15 mm in A. reyesi; fide Wilson 1964), and a differently structured propodeum (propodeum of A. reyesi without transverse ridge separating dorsal and posterior face; fide WILSON 1964).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Philippines.

Castes
Known only from the worker caste.

Nomenclature

 * . Aenictus carolianus Zettel & Sorger, 2010b: 121, figs. 9-12, 13 (w.) PHILIPPINES (Cebu I.).
 * Status as species: Jaitrong & Wiwatwitaya, 2013: 98 (in key).

Worker
Holotype: BL 3.10 mm; HW 0.64 mm; HL 0.71 mm; CI 90; SL 0.56 mm; SI 87; ML 1.02 mm; PHL 0.25 mm.

Paratypes (n = 10): BL 2.95-3.15 mm; HW 0.59-0.64 mm; HL 0.69-0.72 mm; CI 86-90; SL 0.52-0.56 mm; SI 84-90; ML 0.97-1.04 mm; PHL 0.22-0.27 mm.

Colour: Body mainly dark brown, almost blackish. Anterior of head, ventrolateral areas of mesosoma, petiole, postpetiole and sides gaster rather medium brown; apex of abdomen pale brown. Antenna and legs medium brown, scape and femora partly infuscated.

Pilosity: Long to very long setae scattered all over body and appendages, except sides of mesosoma, petiole and postpetiole. Longest setae on occiput and pronotum. A few short setae, often almost appressed, present on dorsum of head and sides of mesosoma.

Structural characteristics: Head mainly smooth, except for hair pits; area between the two parafrontal carinae densely reticulate; area between parafrontal carina and mandible delicately reticulate, in some specimens intermixed with some elongate rugae. In full face view occipital margin straight; occipital tubercles lacking; distinct ridge visible in dorsocaudal aspect. Parafrontal ridge well developed, ca. 0.3 mm long, with small tooth next to antennal sockets. Clypeus angularly produced in middle. Dorsal face of mandibles densely striate. Scape rather long, flagellum short and thick. Mesosoma with almost straight dorsal outline: Pronotum anteriorly down-curved, posteriorly forming a continuous straight line with mesonotum; metanotal impression hardly traceable. Propodeum with almost straight dorsal outline, only most posterior part down-curved, separated by a fine ridge from concave posterior face. Propodeal ridge low approximately semicircular in caudal aspect. Dorsum of pronotum and mesonotum smooth except for hair pits. Most anterior part of pronotum reticulate, narrow lateral margins also reticulate, reaching back to posterior margin; other lateral areas of pronotum variable, either smooth or with faint, superficial reticulation. Mesopleuron continuous with mesonotum (without ridge as in A. pangantihoni). Mesopleuron and metapleuron with longitudinal striation, partly shiny, only their most ventral parts reticulate. Propodeum dorsally smooth, posterior face and a very narrow zone anterior of propodeal ridge densely reticulate. Both petiole and postpetiole short, narrow in dorsal aspect, reticulate except dorsum of nodes smooth; subpetiolar process absent. Postpetiole with sharp anteroventral edge. Gaster smooth except for hair pits; most anterior parts of tergite 1 and sternite 1 reticulate.

Type Material
Holotype worker (in University of San Carlos, Cebu City, The Philippines) and 48 paratype workers (in University of San Carlos, Cebu City, The Philippines; Natural History Museum Vienna, Austria; coll. D. M. Sorger, Vienna, Austria; coll. H. & S. V. Zettel, Vienna, Austria) from Philippines, Cebu City, Cantipla-I Forest Reserve, 1.III.2008, leg. H. Zettel & C. V. Pangantihon (# 512)

Etymology
The species epithet is an adjective and refers to Saint Charles Borromeo (Carolus Borromeus, 2.X.1538 – 3.XI.1584), the great patron of ecclesiastical training in the Renaissance and patron of the University of San Carlos in Cebu City. Since the foundation of the biological collections by the German priest, Father Heinrich Schoenig (2 March 1912 – 18 December 1989), the University of San Carlos has a renowned tradition in classical entomology and takes care of the best insect collection from Cebu Island and from the entire Visayas Region.

References based on Global Ant Biodiversity Informatics

 * Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.