Camponotus opaciventris Mayr 1879: 648 (w.) Syntype workers: Kolkata, India [NHMW]. [Camponotus opaciventris Smith 1873: viii. Nomen nudum, attributed to Mayr]. Combination in Camponotus (Orthonotomyrmex): Emery 1925: 126. Junior synonym of Camponotus sericeus: Bingham 1903: 376. Subspecies of Camponotus sericeus: Forel 1892: 223; Emery 1896: 376; Forel 1908: 6; Emery 1925: 126; Radchenko 1996: 1197. Raised to species: Dietrich 2004: 326; here confirmed.

Worker Fig. 1

Morphometric data: HL 1.52-2.58; HW 1.44-2.85; EL 0.45-0.66; SL 1.45-1.94; PnW 1.30-2.14; ML 2.10-3.16; MTL 1.32-1.94; HTL 1.86-2.79; PL 0.40-0.57; GL 2.02-3.69; TL 6.04-10.00 mm. Indices: CI 95-110; SI 68-101; REL 26-30 (n=25).

Head triangular, wider than long in major worker, lateral margins arched, posterior margin transverse to gently convex; scapes short, surpassing posterior margin of head by less than one-fifth their length; head of minor worker subquadrate longer than wide, with gently arched lateral margins and convex posterior margin; scapes of minor worker longer, surpassing posterior margin of head by one-fourth their length; clypeus subcarinate; anterior clypeal margin emarginate in major worker, convex in minor worker not projected beyond anterior margin of gena; anterolateral corners broadly rounded; mandibles subtriangular, robust, armed with 5-teeth.

Mesosomal outline in profile interrupted at deep metanotal groove; promesonotum forming a regular convexity, metanotum forming an angle with mesonotum; basal portion of propodeum horizontal or slightly concave; apical portion excavate; propodeum forming acute angle with declivous face; propodeal spiracle elongate, slit-like; petiole nodiform, in profile, uniformly wide anteroposteriorly, dorsally rounded; hind tibiae tubular.

Body opaque: head, mesonotum and gaster microreticulate, reticulations feebler on mesopleuron, petiole, scapes and legs; mandibles punctured.

Body covered sparsely with short appressed pubescence, denser on gaster but not hiding the cuticular sculpture; whole body covered with erect setae; setae on propodeum denser than promesonotum; hindtibia with irregular multiple rows of spiny bristles in addition to 3-4 suberect setae at distal end near spurs.

Head and antennae reddish, remainder of body dull black.

Queen Fig. 2a, b, c

Morphometric data: HL 2.34-2.46; HW 2.52-2.55; EL 0.69-0.75; SL 1.88-1.90; ML 3.96-3.97; MTL 1.86-1.92; HTL 2.69-2.73; PL 0.60-0.63; GL 5.27-5.39; TL 12.17-12.45 mm. Indices: CI 104-108; SI 75-80; REL 29-30 (n=2).

As in major worker, with modifications expected for caste and the following differences: head squarer than in major worker; mesosoma and gaster densely pubescent; mandibles 5-toothed; scutum and scutellum with shallow widely spaced punctures; declivous face right angle.

Male Fig. 2d, e, f

Morphometric data: HL 1.30-1.34; HW 1.30-1.33; EL 0.56-0.57; SL 1.44-1.47, ML 3.48-3.49; MTL 1.76-1.78; HTL 2.21-2.26; PL 0.43-0.45; GL 3.40-3.49; TL 8.61-8.77 mm. Indices: CI 99-100; SI 108-113; REL 42-43 (n=2).

Head wider than long including eyes; scapes long, surpassing posterior margin of head by about two-fifths their length; clypeus subcarinate in middle with nearly transverse anterolateral corners; mandibles slender, curved strap like, apical tooth acute, remainder without any teeth or denticles; when closed their tips overlap.

In anterior view, petiolar dorsal margin with two subtle apices; propodeal declivity smoothly rounded; propodeal spiracle elongate, slit shaped.

Pygostyles distally setose; basimeres large, broad at the base with bluntly rounded apex; in dorsal view, telomeres elongate anteroposteriorly and curved inward; in lateral view tubular, rounded apically covered by punctures; basimeres with sparse setae, telomeres abundantly setose; cuspides small bent toward digiti; digiti much longer than cuspides, about 2 times the length of cuspides bent towards each other apically; penisvalva projecting with apices of each penisvalva directed posterolaterally.

Vestiture as in major worker with following differences: propodeum shiny without any setae on dorsum; gaster less pubescent than in other conspecific castes.

Colour dull black; gena, mandibles and antennae brownish.

These ants have been observed to form nests in sandy soils, dry soils and under large stones. The minor workers were collected largely individually at foraging while most of the major workers remained inside the nests.

Camponotus opaciventris most resembles to and is often confused with C. sericeus (Fig. 3) from which it is distinguished by the reddish head (vs. blackish) and gaster without a dense layer of pubescence obscuring cuticular sculpture (vs. dense pubescence layer present and obscuring the cuticular sculpture underneath). Camponotus opaciventris seems to be general in distribution in the Western Himalayas (mostly restricted upto the altitudes of 1200 m). However, C. opaciventris has also been reported from other parts of India occurring sympatrically with C. sericeus which eludes the possibility that C. opaciventris is simply differentiated due to allopatric reduction of gene flow (Forel 1892, Narendra 2006, Akbar 2014). The two species seem to retain their distinctiveness whenever they occur in sympatry. On the other hand C. sericeus is widespread in most of the India but does not seem to extend its distribution in the Western Himalayas. On reexamining the material of earlier records published from Western Himalayas it becomes apparent that C. opaciventris has been misidentified as C. sericeus. The character differences observed for both the species are consistent throughout the range and there is definitely no overlap of characters and no indication for intraspecific variation.