Camponotus inquilinus

This species is known from two artificial nests (wooden stakes with a cavity) placed out in the vicinity of Kuala Belalong Field Studies Centre, Brunei Darussalam, Borneo. One nest was a pure colony and the other was a single minor worker living within a colony of an undescribed Colobopsis species.

Identification
Minor worker: Bicoloured species; head and mesosoma reddish brown, the latter in some specimens with infuscated areas; gaster black. Entire dorsum with long standing setae. Vertex hardly domed. Clypeus basally slightly emarginated, with median carina in basal half. Flagellum of normal length. Pronotum reticulated, on shiny sides sculpture slightly reduced but still visible; with long standing setae. Dorsal outline of pronotum moderately convex, of mesonotum and anterior propodeum straight.

Major worker: Colour similar as in minor, but head rather yellowish clay-coloured. Setae on head very short, on mesosoma, petiole and gaster moderately long. Head squared, sculpture consisting of large punctures and very fine reticulation on frons, vertex and sides where the punctures are spaced. Eyes small. Frontal carinae high. Clypeus and genae with confluent punctures, giving the head a rugose appearance. Sculpture of mesosoma, petiole, and gaster as in minor.

The minor worker of C. inquilinus can be recognized by colour in combination with a normally shaped vertex and long white standing setae on entire dorsum. The major is similarly coloured, except for the yellow head. Its head is very stout, dorsally with short setae and very dense, confluent puncturation, very similar to some species of Colobopsis. In gynes, the head resembles that of the major worker, but with less pronounced features.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Brunei Darussalam.

Biology
Currently, no records of C. inquilinus exist outside of Brunei. All examined specimens were found in artificial nests (#27 and #29) placed in the vicinity of the Kuala Belalong Field Studies Centre (KBFSC) in May 2014. The nests were constructed out of wooden stakes with holes drilled into them to create an internal cavity (for illustrations and details of construction, see Laciny et al. 2017, 2018). Nest #29 contained a colony consisting only of C. inquilinus, which allowed the sampling of minor workers, major workers, gynes and brood. The pupae exhibited cocoons, which is consistent with the current definition of the genus Camponotus (Ward et al. 2016). Nest #27 was occupied by a colony of the undescribed Colobopsis cylindrica group species Colobopsis sp. “nrSA” of the Colobopsis saundersi clade. Within this nest sample, a single minor worker specimen of C. inquilinus was found among minor workers of C. sp. “nrSA” (Laciny et al. 2017). It was presumably mistaken for a conspecific Colobopsis cylindrica group worker during sampling, due to its close resemblance in size and coloration. This finding further strengthens the hypothesis of an inquiline lifestyle closely connected to the exploding ants of the Colobopsis cylindrica group.

Worker
Major

Nomenclature

 * . Camponotus (Myrmamblys) inquilinus Zettel & Laciny, in Zettel, Balàka, et al. 2018: 130, figs. 1-10 (s.w.q.) BORNEO (Brunei).

Worker
Minor

Holotype: HW 1.30; HL 1.41; SL 1.46; SW 0.13; EL 0.45; ML 2.02; HaL 0.29; FeL 1.66; CI 92; SI 112; EI 35; FeI 128. Ward’s Indices: ASM/HWex 0.28; ASM/CLW 0.59; CLW/CLL 1.40. Paratypes (n = 9): HW 1.32–1.52; HL 1.39–1.63; SL 1.41–1.50; SW 0.14–0.16; EL 0.45–0.50; ML 2.02–2.28; HaL 0.29–0.34; FeL 1.45–1.76; CI 90–95; SI 96–111; EI 33–35; FeI 107–129. Ward’s Indices: ASM/HWex 0.28–0.31; ASM/CLW 0.59–0.70; CLW/CLL 1.21–1.53.

Structures: Head roundish, dorsally reticulated and matt; laterally, ventrally, and on vertex with reduced microsculpture and shiny. Lateral outline of eye and head contiguous. Vertex evenly rounded. Frons with shiny midline. Clypeus with very small emargination at middle of basal margin, distal margin protruded in middle, in basal half with shiny median impression. Mandible strongly punctate, with five teeth. Mesosoma slender and low, reticulated and matt, except for shiny sides of pronotum where the microsculpture is reduced to traces; dorsal outline of pronotum and posterior slope of propodeum moderately convex, of mesonotum and anterior part of propodeum straight. Petiole with stocky node, its anterior and posterior face almost parallel, apex strongly obliquely truncated. Gastral tergites with dense reticulation, absent only on very narrow marginal stripes of tergites 3 and 4 (ca. 0.01 mm).

Pilosity: Entire dorsum with long whitish standing setae, longest on propodeum and apex of gaster. Subdecumbent pubescence short, thin, whitish; very sparse on head.

Colour: Head dark reddish brown. Mandibles yellowish. Mesosoma of same colour, but with some variable infuscated areas, in most specimens a large part of propodeum blackish. Petiole dark brown to black. Gaster black. Scape and first funicular segment orange yellow, the following segments black. Legs black, foretibia and -tarsus often paler, brown.

Major

Paratypes (n = 3): HW 1.83–1.91; HL 2.04–2.11; SL 1.22–1.28; SW 0.14–0.19; EL 0.52–0.56; ML 2.35–2.41; HaL 0.24–0.30; FeL 1.57–1.61; CI 89–91; SI 65–68; EI 28–29; FeI 84–86.

Structures: Head squared, slightly longer than wide. Eyes small, laterally not reaching sides of head. Frontal carinae prominent, curved. Vertex and frons with large, widely spaced punctures; interspaces with weak reticulation. Genae and clypeus with very coarse sculpture consisting of confluent large punctures. Clypeus narrow, about twice as long as wide; median carina indistinct; basal margin medially incised, appearing bilobed; anterior margin strongly convex, but not surpassing genae. Mandibles with large punctures and minute micropunctures on interspaces. Mesosoma stouter than in minor worker, but otherwise of similar structure and sculpture. Node of petiole narrow, anterior and posterior faces almost parallel. Gaster similar as in minor.

Pilosity: White standing setae on head very short, on mesosoma, petiole, and gaster distinctly shorter than in minor worker. Subdecumbent pubescence absent from head.

Colour: Differs from minor chiefly by a yellowish clay-coloured anterior portion of the head. In one specimen also the colour of mesosoma tending to yellowish.

Queen
Paratype (n = 1): HW 1.72; HL 1.80; SL 1.28; SW 0.17; EL 0.62; ML 3.20; HaL 0.16; FeL 1.71; OcW 0.11; FWL n.a.; CI 95; SI 75; EI 36; FeI 100.

Structures: Head more similar to major than to minor, but slightly more rounded. Eyes large, surpassing sides of head capsule. Ocelli present. Sculpture similar to major. Mesosoma with gyne-specific features. Pronotum anteriorly and laterally shiny. Wings broken off. Node of petiole narrow, anterior and posterior faces converging, apex rounded. Gaster larger than in workers, otherwise similar.

Pilosity: Similar as in major worker.

Colour: Head colour intermediate between minor and major worker.

Type Material

 * Holotype (minor worker #1122; BRM) from Brunei, Temburong, Kuala Belalong Field Studies Centre, artificial nest 29, 5.IV.2015, leg. A. Kopchinskiy, #346/347.
 * Paratypes (BRM, NHMW): 8 minor workers (#1114–1121), 3 major workers (#1111–1113), and 1 dealate gyne (#1110), same nest series; 1 minor worker (#1173), same locality, artificial nest 27, 16.IV.2015, leg. A. Kopchinskiy, #362.

Etymology
Named after the suspected inquiline lifestyle in nests of Colobopsis cylindrica group ants.

References based on Global Ant Biodiversity Informatics

 * Zettel H., P. Balaka, S. Yamane, A. Laciny, L. Lim, and I. S. Druzhinina. 2018. New mimetic ants from Southeast Asia – the Camponotus (Myrmamblys) inquilinus group (Hymenoptera: Formicidae: Camponotini). Zeitschrift der Arbeitsgemeinschaft Osterreichischer Entomologen 70: 125-174.