Cerapachys wighti, Bharti, Himender & Akbar, Shahid Ali, 2013

Bharti, Himender & Akbar, Shahid Ali, 2013, Taxonomic studies on the ant genus Cerapachys Smith (Hymenoptera, Formicidae) from India, ZooKeys 336, pp. 79-103 : 97-100

Cerapachys wighti sp. n. Figures 5B, 6B, 9A, 38, 39, 40, Table 1

Type material.

Holotype and paratype worker: India. Kerala, Silent valley national park, 11°5'N, 76°26'E, 897m a.s.l., 25.ix.2011, Winkler (coll. Shahid A. Akbar). Holotype in PUAC and paratype in BMNH.

Worker description.

Measurements (holotype in brackets): HL (0.69)-0.71; HW (0.58)-0.59; EL (0.05); SL (0.38)-0.40; WL (0.66)-0.70; MH (0.43)-0.47; PrW (0.33)-0.35; PL1 (0.28)-0.29; PW1 (0.32)-0.33; IIIAL (0.41)-0.44; IIIAW (0.47)-0.49; IVAL (0.71)-0.72; IVAW (0.66)-0.68 Indices: CI 83-(84); SI (65)-67; PI 113-(114).

Head rectangular, longer than broad; sides rounding posteriorly, vertexal margin transverse, posterior lateral corners gently rounded, weakly acute. Parafrontal ridges raised, prominent. Eyes reduced. Mandibles subtriangular; masticatory margin without a row of small denticles. Lateroclypeal teeth reduced. Antennae 12 segmented; scapes short, clavate.

Mesosoma stout, compact, rectangular in dorsal view; dorsal surface slightly convex, the sides gently rounded without any distinct margin. Declivous face of propodeum with the upper sides margined.

Petiole broader than long, without strong overhanging dorsolateral margins. Anterior and posterior faces transverse. Subpetiolar process stout with hook like ventral margin; no fenestra present. Postpetiole sub trapezoidal, wider behind, posterolateral angles uniformly rounded. Gaster elongate; base of cinctus of first gastral tergite with cross ribs; sting exerted.

Sculpture. Mandibles punctured. Punctures on dorsum of head large, crowded, their diameter as large, or larger than, the average distance separating them. Mesosoma, petiole and postpetiole similarly sculptured. Gaster with smaller sized punctures compared with head, mesosoma and metasoma. Cinctus of 1st gastral with cross ribs.

Vestiture. Body with reduced pilosity; moderate decumbent or subdecumbent hairs. Mostly prominent on postpetiole and gaster. Apical funicular segments and legs with standing hairs.

Colour. Dark reddish brown with mandibles, antennae and legs lighter

Etymology.

The species is named after botanist Robert Wight, who historically explored the area in 1847.

Differential diagnosis.

The new species can easily be separated from most of the Indian species on the basis of the large crowded punctureson its cephalic dorsum, with diameter as large, or larger than, the average distance separating them. Cerapachys wighti shares most characters with Cerapachys indicus , which also has large crowded punctures on cephalic dorsum. However the two species can be easily separated. Cerapachys wighti is smaller in size (HW 0.59 mm), has lighter body colouration and reduced eyes (EL 0.05 mm), while Cerapachys indicus is larger in size (HW 0.77 mm), with darker body colouration and large eyes (EL 0.24 mm).

Ecology.

The species seems to be of rare occurrence as it was encountered only once during the extensive surveys conducted in the area. It was collected from a litter sample taken near the Kuntipuzha river, which drains the entire length of the silent valley national park. With a pesticide free catchment area the region is rich in soil biota and ideal for cryptic ant species.

General discussion.

Herewe present a review of genus Cerapachys from India. 12 species are recognized of which 6 are described as new. Partly for convenience the 12 Indian species are placed into arbitrary groups. Group I species with 12 segmented antennae viz., Cerapachys sulcinodis , Cerapachys anokha , Cerapachys schoedli , Cerapachys seema , Cerapachys indicus , Cerapachys aitkenii , Cerapachys wighti , Cerapachys longitarsus and Cerapachys nayana . Of the 9 species given above the first four i.e., Cerapachys sulcinodis , Cerapachys anokha , Cerapachys schoedli and Cerapachys seema , have the punctures on the dorsum of the head relatively small, separated, with their diameter smaller than the average distance separating them. Among these Cerapachys anokha , with the declivous face of the propodeum lacking cariniform margins, and Cerapachys sulcinodis , with the dorsal surface of the petiolar node with a smooth, median area are distinct species in the group. Cerapachys schoedli and Cerapachys seema are easily separated. Cerapachys seema has dull body colouration, sculpture much more prominent and coarse, pilosity denser and head almost oval, with the anterior and posterior sections of its sides converging, while Cerapachys schoedli is brightly coloured, with sculpture and pilosity reduced and the head rectangular with parallel sides. The next 3 species i.e., Cerapachys indicus , Cerapachys aitkenii and Cerapachys wighti , have the punctures on the dorsum of the head large, their diameter greater than the average distance separating them. Among these Cerapachys wighti has the smallest size (HW 0.59 mm) and relatively reduced eyes (EL 0.05 mm) wereas Cerapachys aitkenii and Cerapachys indicus are easily separated from each other on the basis of body sculpture and colouration. Cerapachys aitkenii has characteristic bicolouration and its body sculpture is foveate, wereas Cerapachys indicus is mostly piceous with bluish iridescent sheen and reduced sculpture. The remaining 2 species i.e., Cerapachys longitarsus and Cerapachys nayana are members of ' Phyracaces lineage’ and easily recognized, with strong overhanging dorsolateral margins to the petiole. The two species are separated from each other on the basis of body colouration. Cerapachys longitarsus has characteristic bicolouration with head brown, trunk red or brown, petiole and postpetiole light to dark reddish and gaster brown or black, while Cerapachys nayana is uniformly black in colour, with mandibles, antennae and legs castaneous. Group II species have antennae with less than 12 segments viz., Cerapachys biroi , Cerapachys alii and Cerapachys besucheti . Among these Cerapachys besucheti has 11 segmented antennae while Cerapachys biroi and Cerapachys alii have 9 segmented antennae. Cerapachys biroi is characterized by its opaque body with closely spaced piligerous punctures, while Cerapachys alii has prominent foveate body sculpture.

Workers grade into a number of “atypical” reproductives. These morphologically “atypical” ant reproductives have been assigned a number of descriptive terms. However Peeters (2012) advocate use of "ergatoid queens" for all wingless reproductives that differ morphologically from workers. These ergatoid queens are formed as a response to selective pressures against long range dispersal and solitary colony foundation ( Peeters and Molet 2010). Ergatoid queens have been reported previously in Cerapachys (Brown, 1975). Here we present ergatoid queens of three more species - Cerapachys nayana , Cerapachys schoedli and Cerapachys seema . In evaluating morphometric data of the three castes of Cerapachys seema i.e. worker, ergatoid queens and queen castes (Fig. 41) it is observed that ergatoid queens are closer to gynes than the workers. Further inference and analysis on the subject is beyond the scope of this paper and would require much more information. However the aim of this review is to add further material for examination for understanding this fascinating aspect of ant biology and to promote more studies in this direction.

Notes.

Cerapachys keralensis Karmaly, 2012 described on the basis of two minor? workers collected from the Palakkad district of Kerala. The new species is highly dubious. The description is minimal, superficial and contains no comparative notes. The photographs are derisory as illustrations supporting the inadequate descriptions. Cerapachys keralensis Karmaly, 2012 is here considered to be a species inquirenda.

Two unpublished new species ( Cerapachys browni and Cerapachys costatus ; Bharti and Wachkoo (in press)) are excluded from this paper. The two species can be easily separates from other reported Indian species. Cerapachys browni shares mostaffinitieswith Cerapachys aitkenii but with black colour (unicolorous), rugo-reticulate sculpture and strongly constricted cintus of gaster. Cerapachys costatus with remarkable costate sculpture, which is not reported in any other Indian species.