Taxonomic studies on genus Tetramorium Mayr (Hymenoptera, Formicidae) with report of two new species and three new records including a tramp species from India with a revised key

Abstract Two new species of Tetramorium Mayr, namely Tetramorium shivalikense sp. n. and Tetramorium triangulatum sp. n. are described. Tetramorium triangulatum sp. n. belongs to the inglebyi-species group and is described based on worker, queen and male caste, while Tetramorium shivalikense sp. n. belongs to the ciliatum-species group and is described based on worker caste only. Three species viz., Tetramorium caldarium (Roger), Tetramorium tonganum Mayr and Tetramorium urbanii Bolton represent first records from India. The male caste is described for the first time in the case of Tetramorium tonganum. Among these, Tetramorium caldarium is a tramp species which extends its limit to India as well. A revised key to the Indian ants of this genus is also provided herewith.


Introduction
Tetramorium Mayr, 1855 is one of the largest genera within the tribe Tetramoriini and is one of the most species rich genera with 477 species (Bolton 2012). The genus has a worldwide distribution with varying species richness among different zoogeographical regions. The greatest number of species (230) has been reported from the Afrotropical region, whereas there are only very few (13) known from the New World. The genus has a good representation in the Palaearctic, Oriental, Malagasy and Indo-Australian regions, although much less compared to the Afrotropical region (Hita Garcia and Fisher 2011). Bolton (1976Bolton ( , 1977Bolton ( , 1979Bolton ( , 1980Bolton ( and 1985 revised this genus for most of the above stated regions except the Palaearctic, and noteworthy contributions for the Palaearctic include Steiner et al. (2005), Schlick- Steiner et al. (2006), Csösz et al. (2007), Csösz and Schulz (2010), Steiner et al. (2010). Other significant contributions to this genus dealing with revision of species groups and complexes from the Palaearctic, Afrotropical and Malagasy regions are Csösz et al. (2007), Csösz and Schulz (2010), Hita Garcia et al. (2010), Hita Garcia and Fisher (2011).
In India, the genus Tetramorium is currently represented by 30 species (Bharti 2011). Most of the Indian species were treated by Bolton (1976Bolton ( , 1977 in his revisionary work dealing with the Oriental and Indo-Australian regions. Later, the contributions which reported new species included Mathew (1981), Sheela and Narendran (1998), Mathew and Tiwari (2000), and Bharti (2011) who provided a replacement name for T. browni Tiwari. Fourteen species out of 30 described hitherto have been reported from Southern India, 3 from North-eastern India, 2 from North India, 1 from Central India. Five Indian species T. indicum Forel, T. obesum Andre, T. smithi Mayr, T. tortuosum Roger and T. walshi (Forel) have wide distribution ranges in South-East Asia. Five tramp species namely T. bicarinatum (Nylander), T. caespitum (Linnaeus), T. lanuginosum Mayr, T. pacificum Mayr, T. simillimum (Smith) are widely distributed in India as well. Thus, the genus is mainly known from the southern region of the country. During the present study two new species T. triangulatum sp. n. and T. shivalikense sp. n. are described from the northern part of the country. The three species T. caldarium (Roger), T. tonganum Mayr and T. urbanii Bolton represent first records from India. Moreover, T. caldarium is a well established tramp species and T. tonganum a probable tramp species. Male caste of T. tonganum is described for the first time.

Materials and methods
The ants were collected by pitfall traps, hand picking, soil core sampling, beating vegetation, and from the leaf litter with Winkler's extractor. The digital images of these specimens were prepared on a Nikon SMZ-1500 stereo zoom microscope using Auto-Montage software. Later, images were cleaned with Adobe Photoshop CS5.
Abbreviations of the type depositories are as follows: BMNH, The Natural History Museum, London, U.K.; PUPAC, Punjabi University Patiala Ant Collection, Patiala, India. Two paratypes of each, T. shivalikense sp. n. and T. triangulatum sp. n., will be deposited in BMNH.

Tetramorium shivalikense
Head longitudinally rugose with few cross-meshes up to vertex, posteriorly reticulaterugose, interrugal space punctured and shiny; frontal carinae strongly developed and somewhat short to reach posterior head corners; mandibles longitudinally rugulose and interrugal space smooth and shiny; clypeus with a strong median carina continued to vertex and two weak lateral carinae; dorsum of mesosoma reticulate-rugose; sides of mesosoma rugo-reticulate but weaker sculptured than dorsum; dorsum of node with an unsculptured median longitudinal strip and sides with weak rugosity; dorsum of postpetiole smooth and shiny, sides with weak rugosity; propodeal declivity, gaster and legs smooth and shiny.
Body darker brown in most specimens and few specimens yellowish brown; Whole body covered with abundant, long, erect and short subdecumbent pilosity; antennal scapes and hind tibiae with short suberect hairs.
Etymology. The specific epithet refers to the collection area.
Ecology. This new species is widespread in the Shivalik range of the north-western Himalaya and was collected from soil and leaf litter.
Remarks. This new species belongs to the ciliatum-species group (Bolton 1977) which is distributed in the Oriental and Indo-Australian regions. The characteristics of this group are: antennae 12-segmented, sting appendage triangular or dentiform, anterior clypeal margin entire and not notched or indented medially, frontal carinae extending well beyond the level of the posterior margins of the eyes, propodeal spines long and usually strongly developed, never downcurved along their length, anterolateral gastral corners not projecting forward as a pair of blunt teeth or horns which go round the sides of the posterior portion of the postpetiole.
Tetramorium shivalikense sp. n. is somewhat allied to T. zypidum Bolton. However, it can be easily distinguished from T. zypidum by the following combination of characters: anterior margin of clypeus is entire and convex, petiolar node slightly broader than long in dorsal view while in T. zypidum the anterior clypeal margin is shallowly impressed medially and the petiolar node significantly longer than broad. Other significant characters of T. shivalikense sp. n. which differentiate it from T. zypidum include eyes located laterally at mid-length of the head, propodeal lobes broadly triangular and acute, SI 62.50-66.04, sides of postpetiole with weak rugosity, frontal carinae strongly developed and somewhat short to reach posterior head corners. In T. zypidum the eyes are situated in front of the middle of the sides of the head, the propodeal lobes narrowly triangular and acute, SI 69.00-75.00, sides of postpetiole smooth, and the frontal carinae extend to the posterior head corners and are weak behind the level of the eyes. Head longer than broad, sides weakly convex or almost straight with rounded posterolateral corners, broader posteriorly than anteriorly; posterior head margin straight; clypeus convex with steep apical half; anterior margin of clypeus with a nar-row transverse plate like fringe and somewhat impressed medially; mandibles triangular with 7 teeth, masticatory margin of mandibles with large apical and preapical tooth; third tooth slightly smaller than the preapical tooth followed by 4 denticles; frontal lobes weakly developed, frontal area indistinct; antennal scrobes absent; eye small in size, located laterally and below mid-length of head, composed of single ommatidium; antennae slender, 12-segmented; scape not reach to posterior head margin and 0.63× head length; mesosoma slightly longer than head, broader anteriorly than posteriorly, dorsum flat, tapering backwards; pro-mesonotal suture and metanotal groove indistinct; propodeal spine short (PSL 0.07mm), triangular, acute, divergent and slightly longer than propodeal lobes; propodeal lobes triangular and acute; posterior declivity of propodeum short, concave; petiolar node as broad as long in dorsal view; weakly convex dorsum in lateral view; peduncle short, with a large, straight lamella ventrally; postpetiole broader than long, base of first gastral tergite concave behind the postpetiole, anterolateral corners prominent and projecting forward as a pair of blunt teeth or horns which go round the sides of the posterior portion of the postpetiole, gaster oval.
Head longitudinally rugulose, interrugal space somewhat granular, punctured and shiny; frontal carinae very short, ending in front of the level of the eyes; mandibles longitudinally rugulose and finely punctured; clypeus longitudinally carinate and these carinae continued to head sculpture; dorsum of mesosoma longitudinally rugulose and interrugal space somewhat granular, punctured; sides of mesosoma finely rugoreticulate; petiole and postpetiole mostly smooth with traces of rugosity; propodeal declivity with traces of fine transverse rugosity, base of first gastral tergite longitudinally rugulose; legs smooth except coxae faintly punctured. Body yellowish brown; whole body covered with long and short, erect and suberect pilosity; antennal scapes and hind tibiae with short suberect hairs.
Queen description. Head slightly longer than broad, sides convex, posterior head margin convex, with three ocelli; mandibles with well developed 5 pointed teeth but in few specimens large apical teeth followed by series of denticles; clypeus convex and its anterior margin entire, convex with a narrow transverse plate like fringe and not impressed medially; frontal lobes reduced; antennae 10-segmented; scape short and not reach to posterior head margin and almost 0.46× times head length; apical segment longer and twice of preapical segment, followed by 4 segments as long as broad; then followed by a segment slightly longer than broad; antennal segment attached to pedicel much longer and almost equal to apical segment which then followed by a small segment (smaller than all flagellar segments); antennal scrobes absent; eyes large, convex, situated laterally and more towards lower half of head; pronotum broader than head with rounded anterior lateral angles; mesoscutum and mesoscutellum flat; propodeal dorsal face flat and oblique with vertical declivitous part; propodeal spines absent; propodeal lobes almost rounded; petiole longer, almost 1.4× times its width, with a ventral lamella along its entire length; Postpetiole broader than long; gaster convex, elongate, oval; longer legs.
Head and clypeus longitudinally rugulose and spaces between them punctured; mandibles punctured, frontal carinae continued to the posterior ocelli; dorsum and sides of mesosoma smooth and shiny except propodeum; propodeum finely longitudinally rugulose and punctured; node of petiole, postpetiole, gaster and legs smooth and shiny except few trace of sculpture on sides of node of petiole; wings transparent.
Body yellowish brown with 1 st gastral tergite much darker and area of ocelli blackish; body covered with short and long suberect pilosity.
Etymology. The specific epithet refers to the triangular propodeal spines.
Ecology. This species is uncommon in the Shivalik range of the north-western Himalaya and was collected from soil.
Remarks. Tetramorium triangulatum sp. n. belongs to the inglebyi-species group (Bolton 1977) which is apparently restricted to India and is easily characterized by antennae 12-segmented, appendage of sting triangular or dentiform, frontal carinae absent or very short, not reaching the level of the anterior margin of the eyes, eyes small, reduced to a single ommatidium in myops, antennal scrobes absent, base of first gastral tergite strongly concave in dorsal view, the anterolateral angles of the sclerite angular, produced as a short tubercles or tooth on each side of the posterolateral corners of the postpetiole.
This new species is close to Tetramorium myops Bolton as both species possess short frontal carinae, minute eyes, peduncle with ventral lamella and an medially impressed anterior clypeal margin. However, this new species can be easily distinguished from T. myops by the following combination of characters: T. triangulatum sp. n. has short propodeal spines (PSL 0.07mm), triangular and divergent, peduncle with a large and straight lamella ventrally, dorsum of mesosoma longitudinally rugulose, base of first gastral tergite longitudinally rugulose, while in case of T. myops the propodeal spines are long and upcurved along their length, the peduncle with a large rounded and convex lamella ventrally, dorsum of mesosoma with longitudinal rugulae and reticulation, base of first gastral tergite with vestiges of superficial sculpture. Some of the other significant characters of T. triangulatum sp. n. which differentiate it from T. myops are: head broader posteriorly with straight sides and SI 71.11-75.00 versus head with convex sides and SI 77.00-83.00 in T. myops. Head longer than broad, sides almost straight, posterolateral corners rounded, posterior head margin shallowly emarginated; clypeus consisting of flat basal half and steep apical half; anterior margin of clypeus entire without median notch; mandibles triangular, with 6 teeth, masticatory margin of mandibles with large apical and preapical tooth; third tooth slightly smaller than the preapical tooth followed by three denticles; frontal lobes weakly developed and elevated laterally, frontal area indistinct; antennal scrobes feeble, indistinct, very little concave and not bordered posteriorly; eye moderate in size, located laterally and almost at mid-length of head, composed of ca. 8 ommatidia in a series along its maximum length; antennae slender, 12-segmented; scape short from posterior head margin by one fourth of its length; mesosoma longer than head, broader anteriorly than posteriorly, dorsum flat and tapers to backward in lateral view; pro-mesonotal suture and metanotal groove indistinct; propodeal teeth small (PSL 0.03-0.05mm), acute, triangular almost equal to its width and propodeal lobes; propodeal lobes broad and roughly triangular in shape; posterior declivity of propodeum short, concave; petiole with a short peduncle, its node as broad as long with anterior and posterior faces parallel, weakly convex dorsum in lateral view; ventrally petiole weakly downcurved along its length; peduncle with a small anteroventral lamella; postpetiole broader than long, gaster oval.
Head feebly longitudinally rugose, interrugal space weakly granular or punctulate; frontal carinae feeble and developed to the level of the midlength of the eye behind which fade out or broken; mandibles weakly longitudinally rugulose; clypeus with a strong mid and two lateral carinae; dorsum of mesosoma weakly granular or punctulate with traces of rugulose sculpture; sides of mesosoma reticulate; petiole and postpetiole faintly rugulose and punctulate; propodeal declivity reticulate, upper half finely transversely rugulose, gaster unsculptured; legs smooth and shiny.
Whole body yellowish brown with gaster darker brown; body with short, erect, stiff, blunt hairs and few scattered pubescence on gaster; antennal scapes and hind tibiae with very short, fine, appressed pubescence.
Remarks. Being tramp, it was collected from a disturbed area with high anthropogenic activities. It is widely distributed in the tropics and subtropics, associated with man and living in hothouses, zoos or other constantly heated buildings (Bolton 1980). It is uncommon in India and has been reported for the first time from India. It belongs to simillimum-species group (Bolton 1980, Hita Garcia andFisher 2011) and is very close to T. simillimum (Smith). From the latter, it can be distinguished by the following Head slightly longer than broad, sides almost straight with rounded posterolateral corners, slightly broader posteriorly than anteriorly; posterior head margin straight with shallow median notch; clypeus convex with steep apical half; anterior margin of clypeus entire without median notch; anterior margin of clypeus with a narrow transverse plate like fringe and having convex anterior margin; mandibles triangular, masticatory margin of mandibles with 7 teeth, large apical and preapical teeth; third tooth slightly smaller than the preapical tooth, fourth tooth smaller than the following teeths; frontal lobes weakly developed and slightly elevated laterally, frontal area distinct; antennal scrobes shallow; eye moderate in size, located laterally and almost at mid-length of head, composed of ca. 38-40 ommatidia; antennae slender, 12-segmented; scape long and just fail to reach posterior head margin; mesosoma longer than head, broader anteriorly than posteriorly, dorsum convex; pro-mesonotal suture and metanotal groove indistinct; propodeal spine longer (PSL 0.07-0.10mm) than propodeal lobes, acute, divergent, directed upwards; propodeal lobes broadly triangular; posterior declivity of propodeum short, concave; petiole with a long peduncle, node subglobular in dorsal view; ventrally petiole downcurved along its length, peduncle with an antero-ventral minute blunt teeth; petiole and postpetiole almost equally broader; gaster oval.
Body yellowish brown while gaster somewhat darker; body covered with suberect abundant hairs of varying length; antennal scapes and hind tibiae with decumbent short pubescence.
Queen description. Measurements (queen Similar to the worker in structure, sculpture and pilosity except the following characters (besides characters related to wings ): eyes large in size and with ca.10-12 ommatidia in a series along its maximum length, head with three ocelli, dorsum of mesosoma flat, propodeal spines slightly longer, petiolar node transverse, broad, pronotum reticulate; mesoscutum, mesoscutellum, anepisternum and sides of propodeum longitudinally rugulose; katepisternum smooth, base of propodeum transversally rugulose; petiolar node rugo-reticulate; postpetiole smooth with traces of sculpture on sides, coxae with faint transverse rugulae.
Male description. Head slightly longer than broad, sides convex, posterior head margin straight or weakly convex, with three ocelli; mandibles with well developed 6 pointed teeth; apical tooth large followed by 5 short teeth; clypeus convex and its anterior margin entire, convex with a narrow transverse plate like fringe and not impressed medially; frontal lobes reduced; antennae 9-segmented; scape short and not reach to posterior head margin and almost 0.5x times head length; apical segment longer and more than twice of preapical segment; second flagellar segment longer than scape (0.34mm); antennal scrobes absent; eyes large, convex, situated laterally and more towards lower half of head; pronotum broader than head with rounded anterior lateral angles; mesoscutum convex and mesoscutellum flat; propodeal dorsal face flat and oblique with vertical declivitous part; propodeal spines absent; propodeal lobes almost rounded; petiole longer, almost 1.4× times its width, petiolar node subglobular and medially sulcate shallowly; Postpetiole slightly broader than long; gaster convex, broadly oval; longer legs.
Head and clypeus longitudinally rugulose and spaces between them punctured; mandibles smooth with traces of sculpture, frontal carinae continued to the each side of anterior ocellus; dorsum and sides of mesosoma mostly smooth with traces of sculpture and shiny except propodeum; propodeum finely longitudinally rugulose and punctured; node of petiole longitudinally rugulose except median sulcate region; postpetiole, gaster and legs smooth and shiny; wings transparent.
Body yellowish brown except 1 st gastral tergite brownish and area between ocelli blackish; body covered with short and long suberect pilosity.
Remarks. This species has been found to be widespread in the Shivalik range of the north-western Himalaya and represents a new record for India. Its male caste has been described for the first time. This species belongs to the tonganum-species group (Bolton 1977) and resembles T. difficile Bolton. It can be distinguished from the latter due to larger size, relatively longer antennal scape, longer legs, broadly rounded pronotal corners and propodeum with long spine.  PeNI 46.67,.

Tetramorium urbanii
Head longer than broad, sides almost straight, rounded posterolateral corners, posterior head margin straight, very feebly indented medially; clypeus consisting of slightly convex basal half and steep apical half, without anteromedian indentation; anterior margin of clypeus with a narrow transverse plate like fringe and having convex anterior margin; mandibles triangular, with 7 teeth, masticatory margin of mandibles with large apical and preapical tooth; third tooth slightly smaller than the preapical tooth followed by four denticles; frontal lobes weakly developed and elevated laterally; frontal area deep, forming concavity behind clypeus, broader than long; antennal scrobe distinct, strongly margined dorsally by the frontal carina; eye moderate in size, located laterally and at mid-length of head, composed of ca. 9-10 ommatidia in a series along its maximum length; antennae slender, 11-segmented; scape reaching to posterolateral corners of head; mesosoma longer than head, broader anteriorly than posteriorly, dorsum convex in lateral view; pro-mesonotal suture and metanotal groove indistinct; propodeal teeth small (PSL 0.06mm), triangular, almost equal to its width and propodeal lobes; propodeal lobes narrowly rounded; posterior declivity of propodeum short, slightly concave, separated from dorsum by a strong transverse carina; petiole with a short peduncle, its node longer than broad with convex dorsum, broader behind than front; ventrally petiole downcurved along its length; postpetiole slightly broader than long, gaster oval.
Head longitudinally rugose with few cross meshes; interrugal space punctured and somewhat shiny; frontal carinae strongly developed, almost straight, divergent at eye level, running back almost to the posterior head margin; antennal scrobes feebly sculptured; mandibles longitudinally striate; clypeus longitudinally rugulose; promesonotal dorsum mostly unsculptured smooth and shiny with traces of rugulose sculpture towards the sides and posteriorly; propodeum reticulate, sides of mesosoma longitudinally rugulose; petiole and postpetiole longitudinally rugulose; propodeal declivity and gaster smooth and shiny; legs smooth. Whole body blackish brown except mandibles, antennae and legs yellowish brown. Whole body covered with abundant, long, erect and short subdecumbent pilosity; antennal scapes and hind tibiae with short subdecumbent hairs.
Remarks. T. urbanii belongs to the tortuosum-group (Bolton 1977). It has very short propodeal spines and moderately long scapes, these characters clearly separate it from the rest of the tortuosum-group species. This species was earlier reported from Bhutan and represents a first record from India.