First verified record of the ant genus Calyptomyrmex (Hymenoptera: Formicidae) from India, along with a revised key to known Indomalayan species

Abstract Background The members of genus Calyptomyrmex are mostly encountered under rotten logs, in the soil, under stones and in leaf litter samples. These ants are seldom in collections making estimation of their true distributional patterns problematic (Shattuck 2011). The deep antennal scrobes and the unique configuration of the clypeus are distinct to the genus (Bolton 1981). New information Herein Calyptomyrmex wittmeri Baroni Urbani, 1975 is redescribed and reported for the first time from India. This also confirms the first valid published record of the genus from the country. The image hosted by AntWeb as C. vedda (CASENT0280817; AntWeb 2015b) collected by Besuchet, Löbl, Mussard from Kerala, India and identified by Brown is actually C. wittmeri (Brown was uncertain of his determination of C. vedda and cautiously inserted an interrogation point in front of his determination). Two workers recently collected at Salim Ali Bird Sanctuary, Kerala present similarities to the specimen identified by Brown. However, characters as the lack of well-developed promesonotal suture, absence of clavate setae, and narrow petiolar node, concur with the diagnosis of C. wittmeri. A revised key to known Indomalayan species of the genus is provided herewith.


Introduction
Calyptomyrmex is distributed throughout the Afrotropical, Malagasy, Indomalaya, and Australasia regions (Bolton 2015, AntWeb 2015a, Baroni Urbani 1975, Bolton 1981, Shattuck 2011. Most of the species of the genus have restricted distributional ranges, and are found rarely in samples (Bolton 1981). At present, 37 valid species are recognized (Bolton 2015). These ants have bizarre body pilosity which seems to help in camouflage by retention of soil particles within. This convergent behavior is also shared among other distinct species groups (Bolton 1981, Hölldobler andWilson 1986). The genus awaits a global taxonomic revision; significant contributions to the genus include Shattuck (2011) revision of Australasian species of the genus, adding 14 new species. Prior to this, Bolton (1981) revised the Calyptomyrmex fauna of the Afrotropical region describing seven new species and Baroni Urbani (1975) revised the genus from the Indomalayan region describing four new species, and reported the genus for the first time from Indian subcontinent.

Materials and methods
The specimens were collected using Winkler extraction method. Sampling was carried out in Salim Ali Bird Sanctuary, which constitutes an important part of Western Ghats of India. The region is known to harbor several rare and endemic ant species (Bharti and Akbar 2013a, Bharti and Akbar 2013b, Bharti and Akbar 2013c, Bharti and Akbar 2014a, Bharti and Akbar 2014b, Bharti and Akbar 2014c, Bharti and Akbar 2014d. The taxonomic analyses were carried out using Nikon SMZ 1500 stereo zoom microscope. For digital images, an MP evolution digital camera was used on same microscope with Auto-montage (Syncroscopy, Division of Synoptics, Ltd.) software. Later, images were cleaned as per requirements with Adobe photoshop CS6. Description patterns and morphological terminology are detailed below. Measurements (given in millimeters) follow Baroni Urbani (1975), Bolton (1981), Shattuck (2011) include: CFW Clypeal fork width measured as maximum width between fork-like cuticular projection on the anterior-most part of the clypeus; HL Head length is measured from the base of the clypeal fork to the mid-point of the occipital margin, in a straight line in full-face; HW Maximum head width in full face view; CI (Cephalic index) = HW/HL x 100; SL Length of the scape (basal-most antennal segment) excluding the basal constriction and condylar bulb; SI Scape index = SL/ HW x 100; PetL Maximum length of the petiolar node in dorsal view; PetW Maximum width of the petiolar node in dorsal view; PetI Petiolar index = PetW/PetL x 100; PronW Maximum width of the pronotum in dorsal view.

Glossary of terminology:
Clypeal lamella: narrow and thin transverse strip of cuticle found along the anterior clypeal border; also referred to as the clypeal apron or clypeal bilobed fork.
Clypeus: in dorsal view, the anterior sclerite of the head, which consists of narrow lateral portions and a shield-like median portion.
Full-face view: orientation of the head in which the midpoint of the anterior clypeal margin, the mid point of the posterior margin, and the midpoints of the sides are in focus at the same time.
Gaster: abdominal segments 3-7 when only petiole is present or abdominal segments 4-7 when both petiole and postpetiole are present; functionally, the terminal, enlarged tagma of the body.
Mesosoma: the second main body division of an ant. Morphologically, it is composed of the three thoracic segments (pro-, meso-, and metathorax) to which is fused the propodeum.
Metanotal groove: a transverse suture between the mesonotum and the propodeum.
Ommatidium: an individual facet of the compound eye.
Petiole: in Myrmicinae, the anterior-most of the two segments separating the mesosoma and the gaster. This is one of the defining features of ants. Morphologically, it is the second segment of the abdomen.
Postpetiole: morphologically, the third abdominal segment. In strict usage the term postpetiole should only be applied when the third abdominal segment is reduced and separated from the petiole anteriorly and the fourth abdominal segment posteriorly.
Promesonotal suture: the transverse suture across the dorsal face of the mesosoma that separates the pronotum from the mesonotum.
Propodeum: the dorsal posterior plate of the mesosoma. Morphologically, it is the first segment of the abdomen, fused to the thorax. It may have specializations such as spines, teeth, or lobes.
Punctate: describes surface sculpturing composed of round pits, which may be shallow or deep.
Striate: describes sculpturing composed of shallow, parallel grooves or lines. Head globular in full face view, with posterior margin more or less rounded. Clypeus with a broad bilobed fork-like cuticular projection on its anterior-most part. Masticatory margin with 5-teeth. Eyes with 6-8 ommatidia in greatest diameter. Antennae 12segmented with 3-segmented club.

Taxon treatment
Mesosoma short and stubby, forming a continuous arch in profile;promesonotal suture not distinct in dorsal view. Metanotal groove indistinct. Propodeal declivity concave. Propodeum in lateral view with broad triangular spines, somewhat divergent in dorsal view. Petiole penduculate, with stocky petiolar node. In dorsal view, anterior face of petiolar node straight while posterior face slightly concave in the middle.
Mandibles' dorsal face striate along entire length. Dorsum of head having confused network of striations. Underlying surface distinctly punctuate. Mesosoma, petiolar and postpetiolar nodes with irregular, widely spaced striations, which are more prominent along sides of pronotum and dorsal surface of petiole. Gaster with a fine matte appearance.
Hairs on head and body erect, slightly broader in posterior half with sharp or blunt tips.
Colour dark-brown, the antennae and legs slightly lighter.

Diagnosis
The species is distinct in having body covered with hair only sharp or truncated, but virtually never dilated in any way (Baroni Urbani 1975).

Ecology
Specimens of this species were collected through Winkler extraction method from Salim Ali Bird Sanctuary, Kerala.

Biology
The specimens were encountered in leaf-litter samples. Little is known about the biology of the ant. Thin, spatular setae present on the anterior half of first gastral sternite. In dorsal view, petiolar node wider than postpetiole. Color light-brown (Sri Lanka)

Key to Indomalayan species of Calyptomyrmex
C. singalensis 7 Posterior margin of head above the level of antennal scrobe narrower, and the lateral corners more rounded(HW < 1.10mm); body smaller ( Lateral face of mesosoma and dorsal face of head with few, well-defined, broad rugae. In lateral view, petiolar node with strongly carinate dorsoposterior corner. In lateral view, the highest part of the mesosoma is the posterior half of the pronotal dorsal margin (Borneo, Indonesia, Malaysia) C. asper -Lateral face of mesosoma and dorsal face of head with numerous, illdefined, narrower rugae. In lateral view, petiolar node with angulate dorsoposterior corner, but never strongly carinate. In lateral view, the highest part of the mesosoma is the entire pronotal dorsal margin (the entire dorsal margin of the pronotum has the same height) (Borneo, Indonesia, Malaysia) C. ryderae