Research Article |
Corresponding author: Himender Bharti ( himenderbharti@gmail.com ) Academic editor: Brian Lee Fisher
© 2016 Himender Bharti, Alexander Radchenko, Sishal Sasi.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Bharti H, Radchenko A, Sasi S (2016) Socially-parasitic Myrmica species (Hymenoptera, Formicidae) of Himalaya, with the description of a new species. ZooKeys 605: 113-129. https://doi.org/10.3897/zookeys.605.9087
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A new socially-parasitic species, Myrmica latra sp. n. is described based on a queen and male from Indian Himalaya. Its queen differs from other species by the distinctly narrower petiole and postpetiole, blunt and non-divergent propodeal spines, and a darker body colour. The taxonomic position of the three known Himalayan socially-parasitic Myrmica species is discussed, and M. ereptrix
Ants, Taxonomy, social parasitism, Myrmica latra sp. n., M. ereptrix , M. nefaria
More than 100 years ago,
All socially-parasitic ant species have characteristic morphological features that, taken collectively, were termed as the “inquiline syndrome” by
The first true socially-parasitic Myrmica species, M. myrmicoxena Forel, 1895, was discovered in 1869, in a nest of M. lobicornis Nylander, 1846, but was not formally described and named until much later, at the end of the 19th century (
Recently, the lead author of this paper discovered a queen and a male in Himalaya that possess the typical parasitic Myrmica features. Based on differential morphological diagnosis we describe these as a new species Myrmica latra sp. n. Additionally, we have compiled a key for the identification of all three known Himalayan socially-parasitic Myrmica species.
The queen and male of Myrmica latra sp. n. were collected by handpicking from nests of M. aimonissabaudiae Menozzi, 1939, located under stones. Taxonomic analysis was conducted on a Nikon SMZ 1500 stereo zoom microscope with maximum magnification of 112.5×. For digital images, an MP (Micro Publisher) digital camera was used on the same microscope with AUTO-MONTAGE software (Syncroscopy, Division of Synoptics, Ltd.). Later, images were cleaned with HELICON FILTER 5. The holotype and paratype of new species have been deposited in PUAC (Punjabi University Patiala Ant Collection at Department of Zoology and Environmental Sciences, Punjabi University, Patiala, Punjab, India) and can be uniquely identified with specimen-level codes affixed to each pin (PUAC1569803 and PUAC1569804). Measurements were recorded in millimetres on Nikon SMZ 1500 stereo zoom microscope fitted with ocular micrometer. The comparative morphometric data of the species are listed in Tables
Measurements (in mm) | M. latra sp. n. | M. ereptrix | M. nefaria | ||||||
---|---|---|---|---|---|---|---|---|---|
holotype queen | paratype male | holotype gyne | gynes (n=63) | males (n=4) | |||||
mean±SD | min | max | mean±SD | min | max | ||||
HL | 1.23 | 0.795 | 1.20 | 1.13±0.02 | 1.10 | 1.17 | 0.76±0.02 | 0.74 | 0.78 |
HW | 1.08 | 0.63 | 1.06 | 1.01 ± 0.01 | 0.99 | 1.02 | 0.69±0.03 | 0.66 | 0.71 |
FW | 0.57 | -- | 0.56 | 0.53 ± 0.01 | 0.52 | 0.55 | -- | -- | -- |
FLW | 0.54 | -- | 0.57 | 0.51 ± 0.02 | 0.49 | 0.53 | -- | -- | -- |
SL | 0.90 | 0.675 | 0.82 | 0.87 ± 0.03 | 0.82 | 0.92 | 0.54±0.03 | 0.50 | 0.56 |
PL | 0.57 | 0.40 | 0.46 | 0.51 ± 0.02 | 0.48 | 0.52 | 0.39±0.03 | 0.36 | 0.42 |
PW | 0.54 | 0.42 | 0.65 | 0.60 ± 0.03 | 0.58 | 0.66 | 0.39±0.02 | 0.38 | 0.41 |
PH | 0.54 | 0.40 | 0.58 | 0.54 ± 0.01 | 0.53 | 0.54 | 0.39±0.02 | 0.38 | 0.41 |
PPL | 0.48 | 0.375 | 0.49 | 0.45 ± 0.02 | 0.41 | 0.49 | 0.38±0.03 | 0.36 | 0.42 |
PPW | 0.87 | 0.60 | 0.98 | 0.95 ± 0.02 | 0.91 | 0.97 | 0.57±0.04 | 0.53 | 0.60 |
PPH | 0.84 | 0.55 | 0.88 | 0.81 ± 0.04 | 0.78 | 0.89 | 0.50±0.03 | 0.47 | 0.53 |
ESL | 0.21 | -- | 0.19 | 0.21 ± 0.01 | 0.19 | 0.21 | -- | -- | -- |
ESD | 0.48 | -- | 0.56 | 0.54 ± 0.03 | 0.46 | 0.57 | -- | -- | -- |
AL | 2.04 | 1.47 | 1.96 | 1.77 ± 0.02 | 1.74 | 1.78 | 1.35±0.01 | 1.35 | 1.36 |
AH | 1.17 | 0.90 | 0.96 | 1.09 ± 0.03 | 1.06 | 1.14 | 0.87±0.005 | 0.87 | 0.88 |
SCW | 1.17 | 0.996 | 1.06 | 1.03 ± 0.02 | 1.00 | 1.06 | 0.84±0.03 | 0.81 | 0.86 |
SCL | 1.56 | 1.11 | 1.54 | 1.21 ± 0.03 | 1.14 | 1.25 | 0.96±0.03 | 0.93 | 0.98 |
Morphometric indices of the Himalayan socially-parasitic Myrmica species.
Indices | M. latra sp. n. | M. ereptrix | M. nefaria | ||||||
---|---|---|---|---|---|---|---|---|---|
holotype queen | paratype male | holotype gyne | gynes | males | |||||
mean±SD | min | max | mean±SD | min | max | ||||
HL/HW (CI) | 1.14 | 1.26 | 1.13 | 1.12±0.02 | 1.11 | 1.15 | 1.10±0.01 | 1.10 | 1.12 |
FW/HW (FI) | 0.53 | -- | 0.53 | 0.53±0.02 | 0.51 | 0.54 | -- | -- | -- |
FLW/FW (FLI) | 0.95 | -- | 1.02 | 0.96 ± 0.05 | 0.94 | 1.02 | -- | -- | -- |
SL/HL (SI1) | 0.73 | 0.85 | 0.68 | 0.77 ± 0.04 | 0.75 | 0.81 | 0.71±0.06 | 0.68 | 0.77 |
SL/HW (SI2) | 0.83 | 1.07 | 0.77 | 0.86 ± 0.04 | 0.83 | 0.90 | 0.78±0.02 | 0.76 | 0.79 |
PL/PH (PI1) | 1.05 | 1.00 | 0.79 | 0.94 ± 0.06 | 0.91 | 1.00 | 0.99 ± 0.14 | 0.88 | 1.08 |
PL/HW (PI2) | 0.53 | 0.64 | 0.43 | 0.50 ± 0.02 | 0.48 | 0.51 | 0.56 ± 0.02 | 0.55 | 0.59 |
PW/HW (PI3) | 0.50 | 0.67 | 0.61 | 0.59 ± 0.04 | 0.58 | 0.65 | 0.56 ± 0.02 | 0.54 | 0.58 |
PL/PW (PI4) | 1.06 | 0.95 | 0.71 | 0.82±0.03 | 0.77 | 0.87 | 0.99±0.10 | 0.89 | 1.10 |
PPL/PPH (PPI1) | 0.57 | 0.68 | 0.56 | 0.55 ± 0.06 | 0.49 | 0.58 | 0.76 ± 0.11 | 0.68 | 0.84 |
PPH/PPW (PPI2) | 0.96 | 0.92 | 0.90 | 0.88±0.02 | 0.86 | 0.90 | 0.88 ± 0.00 | 0.88 | 0.88 |
PPW/PW (PPI3) | 1.61 | 1.43 | 1.51 | 1.52±0.08 | 1.46 | 1.68 | 1.46 ± 0.04 | 1.40 | 1.46 |
PPW/HW (PPI4) | 0.81 | 0.95 | 0.92 | 0.94 ± 0.04 | 0.92 | 0.98 | 0.82 ± 0.03 | 0.80 | 0.85 |
PPL/PPW (PPI5) | 0.55 | 0.63 | 0.50 | 0.53±0.02 | 0.49 | 0.55 | 0.67±0.05 | 0.63 | 0.72 |
ESL/HW (ESLI) | 0.19 | -- | 0.18 | 0.21 ± 0.00 | 0.21 | 0.21 | -- | -- | -- |
ESD/ESL (ESDI) | 2.20 | -- | 2.95 | 2.61±0.43 | 2.38 | 3.00 | -- | -- | -- |
AL/AH (AI) | 1.74 | 1.63 | 2.04 | 1.78±0.06 | 1.66 | 1.83 | 1.69±0.02 | 1.67 | 1.70 |
SCL/SCW (SCI) | 1.33 | 1.48 | 1.45 | 1.01±0.10 | 0.86 | 1.11 | 1.13±0.02 | 1.12 | 1.16 |
Morphological terminology for measurements (accurate to 0.01 mm) and indices are as follows (see Fig.
HL maximum length of head in dorsal view, measured in a straight line from the anterior point of clypeus (including any carina or rugae, if they protrude beyond the anterior margin) to the mid-point of occipital margin
HW maximum width of head in dorsal view behind the eyes
FW minimum width of frons between the frontal carinae
FLW maximum distance between the outer borders of the frontal lobes
SL maximum straight-line length of scape from its apex to the articulation with condylar bulb
AL (= WL-Weber’s length) diagonal length of the alitrunk (=mesosoma) (seen in profile) from the most antero-dorsal point of alitrunk/mesosoma to posterior margin of propodeal lobes
AH height of alitrunk (= mesosoma), measured from upper level of mesonotum perpendicularly to the level of lower margin of mesopleuron in profile view
PL maximum length of petiole in dorsal view, measured from the posterodorsal margin of petiole to the articulation with propodeum; the petiole should be positioned so that measured points lay on the same plane
PW maximum width of petiole in dorsal view
PH maximum height of petiole in profile, measured from the uppermost point of the petiolar node perpendicularly to the imaginary line between the anteroventral (just behind the subpetiolar process) and posteroventral points of petiole
PPL maximum length of postpetiole in dorsal view between its visible anterior and posterior margins
PPW maximum width of postpetiole in dorsal view
PPH maximum height of postpetiole in profile from the uppermost to lowermost point, measured perpendicularly to the tergo-sternal suture
ESL maximum length of propodeal spine in profile, measured along the spine from its tip to the deepest point of the propodeal constriction at the base of the spine
ESD distance between the tips of propodeal spine in dorsal view
SCW maximum width of scutum in dorsal view
SCL length of scutum+scutellum in dorsal view
Cephalic (CI) = HL/HW
Frontal (FI) = FW/HW
Frontal-lobe (FLI) = FLW/FW
Scape-1 (SI1) = SL/HL
Scape-2 (SI2) = SL/HW
Petiolar-1 (PI1) = PL/PH
Petiolar-2 (PI2) = PL/HW
Petiolar-3 (PI3) = PW/HW
Petiolar-4 (PI4) = PL/PW
Postpetiolar-1 (PPI1) = PPL/PPH
Postpetiolar-2 (PPI2) = PPH/PPW
Postpetiolar-3 (PPI3) = PPW/PW
Postpetiolar-4 (PPI4) = PPW/HW
Postpetiolar-5 (PPI5) = PPL/PPW
Propodeal spine-length (ESLI) = ESL/HW
Propodeal spine-distance (ESDI) = ESD/ESL
Alitrunk (=mesosomal) (AI) = AL/AH
Scutum (SCI) = SCL/SCW.
Although the abbreviations of index names have been used in numerous publications (e.g.
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.
Queen (Figs
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 distinct 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
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 subdecumbent 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.
The queen of M. 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 M. latra shares these features with two already described socially-parasitic Himalayan species, M. ereptrix Bolton, 1988 and M. nefaria Bharti, 2012, it differs from both by in following characters: M. 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 M. 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 M. latra being distinctly smaller than in M. ereptrix (compare Figs
The male of M. 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 M. latraPW/HW = 0.67, PPW/HW = 0.95 and PPL/PPH = 0.68, but these ratios in the non-parasitic species from the smythiesii-group (M. bactriana Ruzsky, 1915, M. fortior Forel, 1904 and M. 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 M. latra morphologically resembles the male of M. nefaria (the males of M. 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
From the Latin adjective latra, meaning robber or thief.
Both queen and male were collected from nests of M. 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%.
Queens
1 | Petiole and postpetiole narrower, PW/HW = 0.50, PPW/HW = 0.81, petiole nearly as long as wide, PL/PW = 1.06 (Figs |
M. latra sp. n. |
– | Petiole and postpetiole wider, PW/HW = 0.58-0.65, PPW/HW > 0.90, petiole distinctly wider than length, PL/PW ≤ 0.87 (Figs |
2 |
2 | Head dorsum with longitudinal rugae and reticulation (Fig. |
M. nefaria Bharti |
– | Head dorsum with longitudinal, somewhat divergent rugae, reticulation present only on vertex and temples (Fig. |
M. ereptrix Bolton |
Males (males of M. ereptrix are unknown)
1 | Head longer, HL/HW = 1.26, distinctly narrowed posteriorly above eyes; head dorsum with short irregular rugae (Fig. |
M. latra sp. n. |
– | Head shorter, HL/HW = 1.10–1.12, gradually arched above eyes; head dorsum with longitudinal rugae (Fig. |
M. nefaria Bharti |
There are two questions that need to be addressed: first, why have we described this queen and male that were collected from different nests as the same species? Secondly, why have we described them as social parasites?
The second question is more easily answered: both castes possess a combination of features known as the “inquiline syndrome” (discussed above) and by these features they significantly differ from all known free-living Himalayan Myrmica species. This species is most unlikely to occur elsewhere, given that the Myrmica fauna of the Himalayan region is almost completely isolated from the fauna of adjacent regions (
We have decided to describe the queen and male as the same species, despite coming from different nests, because the putative host colonies were of the same species, M. aimonissabaudiae, living in the same general region at similar altitudes albeit the two sites were 173 km apart (see Map
Furthermore, it is always better to avoid the description of a new taxon based on a single specimen, especially, if it is collected in isolation (e.g. in a pitfall trap), but in this case the specimens were collected from a nest of same host species and both male and female differ from already known species of the genus. To date, eight Myrmica species have been described based on a single queen (
The present concept of species-groups in the genus which is based on morphology, was outlined by
The molecular genetic analysis published by
Morphologically, female castes of the rugosa and smythiesii groups share several diagnostic features (e.g.: scape very smoothly curved at the base, not angled and with no trace of a lobe or carina; frontal lobes slightly curved, frons wide and frontal lobes not extended; anterior clypeal margin is convex and prominent, without a medial notch). The main difference is the shape of the frontal carinae: in the rugosa-group they merge with the rugae that extend to the occipital margin, do not curve outwards and do not merge with rugae that surround antennal sockets, but in the smythiesii-group frontal carinae curve outwards to merge with the rugae that surround the antennal sockets. In addition, males of the rugosa-group have a relatively short scape, SL/HL < 0.60, but those of the smythiesii-group have much longer scape – SL/HL > 0.70 but unfortunately males are unknown for some species in this group: M. wittmeri, M. bactriana Ruzsky and M. ruzskyana Radchenko & Elmes. If the rugosa- and smythiesii- species groups are quite closely related, then, taking into account the length of scape in males, species placed in the latter group are obviously more evolved, because a short scape is a plesiomorphic state not only for Myrmica, but for ants as a whole (see
Regarding the Himalayan social parasites: when
Probably, M. nefaria is a temporary social parasite as all its castes were found in the host colony and in the right circumstances may potentially form free-living colonies (as in the case of M. vandeli Bondroit, 1920 in Europe (see
Financial assistance rendered by the Department of Science and Technology, Ministry of Science and Technology, Govt. of India, New Delhi (SR/SO/AS- 68/2011) is gratefully acknowledged. Authors also wish to thank Antweb team for images of Myrmica ereptrix (CASENT0900296). We are also sincerely grateful to Dr. G. W. Elmes (U.K.) for the valuable comments to the manuscript of this paper and for the language check.