Aenictus pangantihoni

A. pangantihoni is known only from the type locality. The type locality lies on Camiguin Island in the municipality of Mambajao, in the area of the Katibawasan Falls at the lower slopes of Mt. Hibok-Hibok at an elevation of ca. 350 m a.s.l. (09°12’ N, 124°43’ E). Workers were collected from a trail lined with some bushes and trees in a pasture area.

Identification
A member of the philippinensis species group. Aenictus pangantihoni is most similar in general appearance to Aenictus rabori. However, it is easily distinguished from the latter as follows: smaller than A. rabori (HW 0.78-0.80 mm, TL 4.00-4.10 mm in A. pangantihoni; HW 0.83-0.85 mm, TL 4.35-4.45 mm in A. rabori); seen in profile occipital corner of head round, without protruding lobe (with a lobe in A. rabori); sides of head entirely smooth and shiny (partly superficially shagreened with smooth and shiny interspaces in A. rabori).

Zettel & Sorger (2010) - Head without “Typhlatta spots.” Parafrontal ridge present, up to 0.3 mm long (in some specimens posteriorly reduced and only anterior third, ca. 0.1 mm, distinct). Mandible broad, with a series of minute, indistinct denticles. Antenna 10-segmented. Pronotal humeri unarmed. Mesonotum demarcated from mesopleuron by conspicuous ridge. Metanotum concave, dipping distinctly below mesonotum and slightly below dorsal face of propodeum. Petiole elongate, without subpetiolar process.

The unusual, distinct ridge between mesonotum and mesopleuron closely relates Aenictus pangantihoni to two other Philippine species, Aenictus rabori and Aenictus philippinensis, both described from Negros. Chapman (1963) separates the two species by the dense head punctation of A. philippinensis and by the dorsal ouline of the mesosoma. Wilson (1964) distinguishes these species in his key (couplet 27) by the metanotal impression and the length of the parafrontal ridge. For the parafrontal ridges, Wilson (1964) measures a length of 0.28 mm for A. philippinensis and only 0.17 mm for A. rabori. In A. pangantihoni this ridge is usally long (ca. 0.3 mm), but we have seen specimens in which it is hardly tracable in posterior two-thirds. The metanotal impression is very different in A. rabori and A. philippinensis, being strongly impressed in the latter (see Wilson 1964:). In this character A. pangantihoni resembles A. rabori, but in comparison with this species, a low inpression is present. Moreover, the femora of A. pangantihoni are less strongly dilated than in A. rabori, the petiole is more slender (in dorsal aspect) and with a smooth area at the node’s centre.

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

Castes
Known only from the worker caste.

Nomenclature

 *  pangantihoni. Aenictus pangantihoni Zettel & Sorger, 2010b: 120, figs. 5-8, 13 (w.) PHILIPPINES (Camiguin I.). See also: Jaitrong & Yamane, 2012: 68.

Worker
Holotype: BL 4.00 mm; HW 0.76 mm; HL 0.82 mm; CI 93; SL 0.60 mm; SI 79; ML 1.35 mm; PHL 0.24 mm.

Paratypes (n = 10): BL 3.90-4.20 mm; HW 0.72-0.78 mm; HL 0.80-0.85 mm; CI 90-95; SL 0.76-0.80 mm; SI 76-80; ML 1.31-1.42 mm; PHL 0.22-0.25 mm.

Colour: Almost uniformly medium brown. Each antennomere except scape and ultimate one distally infuscated; flagellum appearing slightly annulate. Scape, ultimate antennomere, legs, nodes of petiole and postpetiole, and gaster (except tergite 1) somewhat lighter than other body parts.

Pilosity: Setae scattered and of relatively uniform lengths, very long setae missing. Long setae distributed almost all over body and appendages, except sides of mesosoma, petiole, and postpetiole. A few short, almost appressed setae present on dorsum of head and sides of mesosoma.

Structural characteristics: Head completely smooth, except for hair pits and narrow reticulate stripe just behind antennal sockets. In full face view occipital margin straight or very weakly convex; occipital tubercles lacking. Parafrontal ridge ca. 0.3 mm long, either continuously developed or interrupted, in such cases its anterior third well developed plus a minute tubercle at the position of the usual posterior end. Clypeus angularly produced in middle. Mandibles punctate (with hair pits). Antennae rather short, flagellum thick. Mesosoma with very characteristic dorsal outline: Pronotum anteriorly sharply down-curved, posteriorly forming a weakly convex bow continuous with almost straight mesonotum; metanotal impression distinct, anteriorly step-like below mesosoma, against dorsal face of propodeum slightly impressed. Propodeum with almost straight dorsal outline sharply separated by a ridge from concave posterior face. Propodeal ridge membraneous, ca. 0.25 mm high, horseshoe-shaped in caudal aspect. Dorsum of pronotum and mesonotum smooth except for hair pits. Most anterior part of pronotum reticulate, narrow lateral margins distinctly canaliculate and reticulate, reaching back to posterior margin; other lateral areas of pronotum either completely smooth or with faint, superficial reticulation. Mesopleuron separated from mesonotum by very sharp, straight ridge. Mesopleuron, metapleuron and propodeum strongly rugous, mat except anterio-ventral parts of meso- and metapleuron slightly shiny. Petiole moderately elongate, narrow in dorsal aspect, subpetiolar process absent. Postpetiole shorter and wider than petiole, its anteroventral edge sharp. Both petiole and postpetiole reticulate except dorsum of nodes smooth. Gaster smooth except for hair pits; most anterior parts of tergite 1 and sternite 1 reticulate.

Jaitrong & Yamane (2012) - Paratype (n = 4): TL 4.00-4.10 mm; HL 0.83-0.88 mm; HW 0.78-0.80 mm; SL 0.55-0.63 mm; ML 1.38-1.43 mm; PL 0.35-0.38 mm; CI 91-95; SI 75-78.

Head in full-face view slightly longer than broad, with sides slightly convex and posterior margin almost straight; occipital margin forming a distinct carina; seen in profile occipital corner of head rounded. Antennal scape relatively short, slightly extending 2/3 of head length; antennal segment II slightly longer than each of III-VI; terminal segment almost as long as VII+VIII+IX. Frontal carinae short fused at the level of antennal base to form a single carina and slightly extending beyond the level of the posterior margin of torulus, poorly developed in posterior half. Parafrontal ridge short, extending less than 1/3 of head length, 0.17 mm long, seen in profile weakly developed in the middle. Masticatory margin of mandible with a large apical tooth followed by a series of 7-9 denticles of two sizes, the larger ones alternating with 1-3 of smaller size. Mesosoma in profile with promesonotum weakly convex dorsally and sloping gradually to metanotal groove; metanotal groove distinct and deep; upper portion of mesopleuron impressed; propodeum slightly lower than mesonotum; propodeal junction right-angled; declivity of propodeum shallowly concave, encircled with a distinct rim. Petiole subsessile, distinctly longer than high; subpetiolar process almost absent; postpetiole as long as petiole (including short pedicel) and almost as long as high, with its node rounded dorsally. Legs relatively short, seen from side with greatly swollen femora.

Head entirely smooth and shiny, except for hair pits; mandible smooth and shiny, with scattered punctures; antennal scape superficially shagreened. Pronotum smooth and shiny except for its anteriormost portion reticulate; lateral face of pronotum smooth and shiny, with a narrow ventral belt that is impressed and reticulate, this belt continuing posteriorly, running along posterior margin of the lateral face, approachingdorsal face of pronotum; mesonotum smooth and shiny; mesopleuron, metapleuron and propodeum densely punctuate/reticulate and mat except for isolated small shiny areas. Both petiole and postpetiole microrecticulate except dorsal faces smooth and shiny. Femora superficially shagreened with smooth and shiny interspaces; tibiae superficially shagreened, partly smooth and shiny.

Head and mesosoma dorsally with relatively sparse standing hairs; longest pronotal hair 0.2–0.25 mm long. Entire body reddish brown.

Type Material
Holotype worker (in University of San Carlos, Cebu City, The Philippines) and 56 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, Camiguin, West of Mambajao, Katibawasan area, 350 m, 15.III.2010, leg. H. Zettel & C. V. Pangantihon (515)

Jaitrong & Yamane (2012) - Holotype (USC) and 56 paratype workers (NHMV,, ) from Philippines, Camiguin, West of Mambajao, Katibawasan area, 350 m a.s.l., H. Zettel and C.V. Pangantihon leg. Four paratype workers in and  were examined.

Etymology
We dedicate this species to Clister V. Pangantihon, who first discovered some foraging workers.