Myrmica latra, Bharti, Himender, Radchenko, Alexander & Sasi, Sishal, 2016

Bharti, Himender, Radchenko, Alexander & Sasi, Sishal, 2016, Socially-parasitic Myrmica species (Hymenoptera, Formicidae) of Himalaya, with the description of a new species, ZooKeys 605, pp. 113-129 : 117-124

Taxon classification Animalia Hymenoptera Formicidae

Myrmica latra sp. n. Figs 2-7, Tables 1, 2

Type-material.

Holotype (PUAC1569803) queen, pinned, point-mounted, "India, Himachal Pradesh: Prounthi, 31.1043, 77.6487, 2260m, Hand picking, 14 July 2013, Joginder Singh leg.". Paratype (PUAC1569804) male (alate), pinned, point-mounted, "India, Himachal Pradesh, Roggling, 32.5514, 76.9704, 2740m, 12 July 2015, Pawanpreet Kaur leg." [PUAC]. Nest understone in ground covered with low vegetation and scattered Pinus and Cedrus trees.

Description.

Queen (Figs 2-4, Tables 1-2). Head somewhat longer than broad, with slightly convex sides and occipital margin and widely rounded occipital corners. Anterior clypeal margin convex, but not strongly prominent and not notched medially. Upper latero-ventral corners of head somewhat angulate, but not strongly pointed (seen in profile). Eyes situated slightly in front of midlength of sides of head, Ocelli well developed. Right mandible with 7 teeth, left mandible with 6, apical tooth the largest, preapical one smaller, and other ones uniform and small. Frontal carinae curved outwards to merge with rugae, which surround antennal sockets. Frons wide, frontal lobes converging anteriorly, so that width of frons somewhat wider than distance between frontal lobes. Antennae 12-segmented, with 5-segmented club, scape slender, gradually and feebly curved at the base, without any trace of lobe or carina, shorter than head width, only slightly surpassing occipital margin.

Mesosoma of moderate length, mesonotum feebly convex, scutum not overlapping pronotum, antero-lateral corners of pronotum visible from above, propodeal lobes rounded apically. Propodeal dorsum almost flat (seen in profile). Propodeal spines quite short, widened at the base, thick, not pointed, but narrowly rounded at tips, directed upward (at an angle ca. 45°) and backward, not diverging when seen from above. Metapleural glands moderately large, with conspicuous orifice dorsally on bulla.

Petiole and postpetiole distinctly widened, while less in width in comparison to other Himalayan socially-parasitic Myrmica species. Petiole high, with short but dis tinct peduncle, slightly longer than wide (in other Himalayan socially-parasitic Myrmica it is distinctly shorter than wide); its anterior surface concave, node dorsum narrowly rounded; ventral process quite small, widely rounded on tip and directed mostly forward and slightly downward. Postpetiole high, more than 1.5 times higher than petiole, and 1.75 times higher than its length, quite thick and with rather widely rounded dorsum, its anterior surface convex, posterior one almost straight (seen in profile); ventral process well developed, subtriangular, narrowly rounded apically. Spurs of middle and hind tibiae well developed and pectinate.

Head dorsum with coarse longitudinal rugosity and reticulation, diverging postero-laterally. Vertex and occiput with transverse rugosity and reticulation; surface between rugae finely punctate, but appearing shiny. Frontal triangle deep, smooth and shiny. Clypeus longitudinally rugose, surface between rugae finely punctate. Mandibles coarsely longitudinally rugose.

Pronotum longitudinally rugo-reticulate and transverse dorsally. Scutum densely longitudinally rugose, only its anterior part smooth and shiny. Anterior part of scutellum with short longitudinal rugae, its posterior part transversely-concentrically rugose. Propodeal dorsum with finer transverse rugae, its declivity smooth and shiny. Mesopleurae and sides of propodeum longitudinally rugose, only posterior part of anepisternum smooth and shiny. Petiolar node and postpetiolar dorsum transversely rugose. Whole surface of mesosoma between rugae densely while not coarsely punctate, appears dull. Gaster very smooth, polished.

Whole body with whitish hairs. Head dorsum, margins and ventral surface with abundant semi-erect to erect straight whitish hairs of various length, anterior clypeal margin with long setae, mandibles with quite long curved hairs, scape and 7 basal funicular segments with abundant semi-erect to subdecumbent long hairs and shorter pilosity, segments of club with very dense subdecumbent pilosity.

Mesosoma, waist and gaster with numerous long and curved erect hairs, combined with shorter suberect to subdecumbent straight hairs.

Whole body brownish-black, mandibles, antennae, legs (especially tibia and tarsi) and sides of pronotum lighter, brownish.

Male (Figs 5-7, Table 1-2). Head distinctly longer than broad, suboval, gradually narrowing behind and in front of eyes, occipital margin convex. Upper latero-ventral corners of head somewhat angulate, but not strongly pointed (seen in profile). Frons somewhat raised up anteriorly and gradually sloping to the level of central ocellus. Clypeus convex, its anterior margin very feebly convex, not prominent and not notched medially. Eyes large in comparison to queen, situated in front of midlength of sides of head, ocelli quite prominent. Mandibles with well-developed apical and smaller preapical teeth, followed by 6 minute blunt denticles. Antennae 13-segmented, with 5-segmented club; scape long, longer than six basal funicular segments and head width, surpassing occipital margin.

Mesosoma long and low, ca. 1.6 times longer than height, scutum and scutellum convex, forming regular arch, scutellum does not project dorsally above scutum when seen in profile. Propodeum gradually rounded, without tubercles, length of its dorsal surface subequal to posterior one, propodeal lobes rounded apically. Petiole with short peduncle, strongly concave anterior surface and widely rounded node dorsum. Postpetiole short and high, ca. 1.5 times higher than length, with evenly rounded dorsum, its sternite looks like a rather long widely rounded ventral plate. Ventral process on petiole small, tooth-like. Both petiole and postpetiole obviously widened. Spurs of middle and hind tibiae well developed and pectinate.

Wing venation almost typical to the genus, e.g. forewing with closed cell mcu, open cell 3r, vein 2+3RS reduced proximally so that cells 1+2r and rm only partly separated.

Head dorsum with irregular short coarse rugae, sides of head and vertex with reticulation. Mandibles smooth, only sparsely punctate, appearing shiny overall. Sides of pronotum mostly smooth, but with fine longitudinal slightly sinuous rugulosity posteriorly. Anterior part of scutum between Mayrian furrows smooth and shiny, its posterior part and scutellum irregularly rugulo-punctate. Anepisternum with irregular fine rugulosity, katepisternum and sides of propodeum coarsely longitudinally rugulose and with fine reticulation; propodeal dorsum and declivity shagreened, somewhat shiny. Petiolar node and postpetiole with fine superficial microsculpture, but appearing more or less shiny. Gaster smooth and shiny.

Whole head surface with numerous long erect to suberect, often curved long hairs and shorter subdecumbent pilosity. Scape and basal funicular segments with subde cumbent to suberect hairs, club segments with subdecumbent short pubescence. Mesosoma and waist with abundant, quite long suberect to erect hairs, gaster with similar long hairs and sparse short subdecumbent pilosity. Legs with numerous subdecumbent, quite long hairs. Whole body and appendages brownish.

Workers. unknown.

Remarks.

The queen of Myrmica latra sp. n. differs from the known non-parasitic Himalayan Myrmica species by possessing characteristic features of the "inquiline syndrome", particularly by the distinctly widened petiole and postpetiole, presence of the well-developed ventral lobe on the petiole and postpetiole, and also by the presence of more hair on the body. Although Myrmica latra shares these features with two already described socially-parasitic Himalayan species, Myrmica ereptrix Bolton, 1988 and Myrmica nefaria Bharti, 2012, it differs from both by in following characters: Myrmica latra has a relatively less-widened petiole and postpetiole, its head is twice as wide as the petiole: PW/HW = 0.50 compared to PW/HW = 0.58-0.65 in the two other species; PPW/HW = 0.81 in Myrmica latra versus a ratio> 0.92 in the other two species. The petiole in Myrmica latra sp. n. is nearly as long as wide (PL/PW = 1.06), but in the other two it is distinctly wider than long (PL/PW ≤ 0.85); the ratios PPL/PPW are 0.55 vs. ≤ 0.55, respectively. Other differences include the ventral processes on the petiole and postpetiole in Myrmica latra being distinctly smaller than in Myrmica ereptrix (compare Figs 3 and 9); its propodeal spines are blunt and not divergent, while in both Myrmica ereptrix and Myrmica nefaria they are pointed and distinctly divergent (compare Figs 3 and 9, 12); the spur on the middle tibiae in Myrmica ereptrix is strongly reduced, while in the other species it is well developed and pectinate; the body colour of Myrmica latra sp. n. is darker than in two other species.

The male of Myrmica latra sp. n. well differs from all the known males of the species of the smythiesii-group (see also Discussion, below) by the much wider petiole and postpetiole, as well as by the distinctly higher postpetiole, its sternite gives the appearance of rather long and widely rounded ventral plate. Thus, in Myrmica latra PW/HW = 0.67, PPW/HW = 0.95 and PPL/PPH = 0.68, but these ratios in the non-parasitic species from the smythiesii-group ( Myrmica bactriana Ruzsky, 1915, Myrmica fortior Forel, 1904 and Myrmica ruzskyana Radchenko et Elmes, 2010) are: PW/HW <0.40, PPW/HW <0.60 and PPL/PPH> 0.80 (our unpublished data).

While the male of Myrmica latra morphologically resembles the male of Myrmica nefaria (the males of Myrmica ereptrix are unknown), it differs by its longer head (HL/HW = 1.26 vs. 1.10-1.12) that is distinctly narrowed posteriorly (compare Figs 5 and 14); by the distinctly longer scape that is longer than the head width in Myrmica latra : SL/HL = 0.85, SL/HW = 1.07 vs.SL/HL = 0.68-0.77 and SL/HW = 0.76-0.79; by the wider petiole and postpetiole (PW/HW = 0.67, PPW/HW = 0.95 vs. 0.54-0.58 and 0.80-0.85). Additionally, the head dorsum in Myrmica latra has short irregular rugae, but in Myrmica nefaria males, the head dorsum has longitudinal rugae; posterior part of scutum has longitudinal rugae vs. transversal rugosity; its propodeum is gradually rounded, without teeth or tubercles, but in Myrmica nefaria propodeum is distinctly angulated with short teeth. Finally, the forewing venation of the male of Myrmica latra sp. n. is almost typical for the genus Myrmica and resembles that of Myrmica ereptrix (see above and Bolton 1988), but in some males of Myrmica nefaria it is modified (see Bharti 2012). However, it should be remembered that the forewing venation in different specimens of the same species, especially in social parasites, may be quite variable so not too much reliance should be placed on this feature (see Arnoldi 1930, 1933; Bolton 1988; our own observations).

Etymology.

From the Latin adjective latra , meaning robber or thief.

Ecology.

Both queen and male were collected from nests of Myrmica aimonissabaudiae built under stones. The ground is covered with low vegetation, and scattered Pinus and Cedrus trees. The recorded nest temperature and humidity at site one, where queen was collected was 18 °C and 76%, whereas at site two, where male was collected, the recorded nest temperature was 19 °C and humidity 66%.