Myrmica myrmicoxena

The type specimens taken in 1869 were, for more than 100 years, the only record for this species. It was found in a nest of Myrmica lobicornis, at altitude 1900 m (probably under a stone). It is probably workerless and almost certainly a social parasite. More recently it has been found a number of times in numerous locations.

Identification
The queens of M. myrmicoxena are most similar to those of Myrmica arnoldii, differing mainly by a somewhat narrower frons and smaller size. We place M. myrmicoxena in the monotypic myrmicoxena species group. (Radchenko and Elmes 2010)

Distribution
Switzerland, northern Italy

Distribution based on Regional Taxon Lists
Palaearctic Region: Switzerland.

Biology
Radchenko and Elmes (2010) - Recently Mike Lush captured a specimen in a Myrmica lobulicornis nest and specimens have been found by different collectors in S Tyrol, Italy and Vallais, Switzerland (Bernhard Seifert, pers. comm.). Mike Lush (pers. comm.) wrote “When I turned over the stone [in alpine grassland] the ants did their normal thing of running around frantically, except for a small cluster of about 20 workers that I eventually realised were holding this queen down, preventing her movement. I didn't wait around to see whether she would escape (it had already been a minute or so whilst I was scanning for interesting things that were actually moving), so pooted her and the workers! She seemed unharmed by her captors, so I assumed that this might be how she acquired the colonies scent and that they were doing it before I overturned the stone”.

Nomenclature

 *  myrmicoxena. Myrmica myrmicoxena Forel, 1895i: 143 (q.) SWITZERLAND. Emery, 1908a: 181 (m.). See also: Forel, 1910a: 29; Finzi, 1926: 114 (misspelled as myrmecoxena); Kutter, 1973c: 255; Kutter, 1977c: 67; Radchenko & Elmes, 2003a: 220; Glaser, Lush & Seifert, 2010: 107; Radchenko & Elmes, 2010: 204.

Radchenko and Elmes (2003) - The queens of M. myrmicoxena are most similar to those of Myrmica arnoldii, a South Siberian and Mongolian species, differing mainly by a somewhat narrower frons and smaller size. Their host species (or possible host species in the case of M. arnoldii) belong to the lobicornis-group of Myrmica species, but they are unlikely to belong to that group because their males have relatively short antennal scape, compared to males of lobicornis-group, which is a feature of the scabrinodis-group. Therefore we place them together in the myrmicoxena-group. However, a close relationship between the European M. myrmicoxena and Central Asian M. arnoldii seems unlikely. One important difference is that the antennae of M. myrmicoxena males (as drawn by Kutter 1977) have the normal 13-joints whereas those of M .arnoldii are 12-jointed. Kutter was normally a careful and accurate draftsman but it is just possible that he drew what he expected to see (13 segments rather than 12), therefore it is important to try and locate the males of M. myrmicoxena to check this feature.

Forel (1874, pp. 78-79) described from the Swiss Alps unusual queens and males of Myrmica, found in a nest of M. lobicornis, but did not give them a name for another 20 years. Then he made an extremely brief description of the queens, calling them M. myrmicoxena (Forel 1895), but he did not include the males to the type series. Emery (1908a) made a formal description of the males, based on Forel's (1874) original description, and Forel (1910, 1915) made further short additions to the description of queens and males. Kutter (1977) made some new notes on M. myrmicoxena and published the first drawings of the queen and male; Seifert (1988) followed Kutter's description. Despite these publications, we remained uncertain about some features of the morphology of M. myrmicoxena and felt that it should be redescribed in a more modern style. We do this for the queens but unfortunately, we have not located the males and can only provide notes of their main features based on the published data.

Queen
Radchenko and Elmes (2003) - Measurements and indices (queens, n = 6) (data of lectotype are in brackets). HL 1.02-1.05 (1.03), HW 0.94-0.97 (0.94), SL 0.67-0.70 (0.67), AL 1.52-1.58 (1.54) mm; FI 0.45-0.46 (0.46), FLI 1.16-1.21 (1.21), SI1 0.65-0.66 (0.65), SI2 0.71-0.72 (0.71), PPI 0.56-0.57 (0:56), ESLI 0.18-0.23 (0.23).

Head longer than broad, with subparallel sides, narrowly rounded occipital corners and straight or at most very weakly concave occipital margin; anterior clypeal margin broadly convex, without medial notch. Frons wide, but frontal carinae distinctly curved and frontal lobes somewhat extended. Antennal scape relatively short, does not reach occipital margin, weakly curved at the base, with no angle or carina.

Alitrunk quite short and high, propodeal spines rather thin, finger-like, slightly extended at the base. Petiolar node in profile subtriangular, without dorsal plate; ventral surface of petiole with small, not extended, narrowly rounded process. Postpetiole wide and high, with relatively small, broadly rounded ventral process.

Spur on middle and hind tibiae reduced, always distinctly shorter than width of tibiae, but varying from relatively long and with short "brush" of bristles to nonpectinate, extremely short and setae-like. The venation of forewing varies from the typical for genus Myrmica with the cubital cell partly separated by short vein and closed distally, to the cubital cell being partly separated by a short vein, but open distally, to the cubital cell being partly separated by a short vein, open distally, but with an additional cross-vein.

Sculpture of whole body quite coarse. Frons with longitudinal, slightly sinuous rugae, occiput and sides of head with reticulation; antennal sockets surrounded by concentric rugae; clypeus with longitudinal rugae. Sides and dorsum of alitrunk with longitudinal rugae. Petiolar node with irregular short sinuous rugae and reticulation, postpetiole dorsally with sparse fine rugosity, more or less smooth. Surfaces between rugae on whole body smooth and shiny.

Head and alitrunk with fairly sparse, straight, standing hairs; petiolar node with less than 10 standing hairs. Appendages with numerous semidecunbent hairs. Head and alitrunk reddish-brown, appendages lighter, reddish-yellow.

Male
Radchenko and Elmes (2003) - (based on Fore1 1874, 1910, 1915; Kutter 1977). Antennae 13-jointed, antennal scape short, SI1 = SI2 = 0.35 (based only on Kutter's 1977 drawing). Head margins with short hairs. Cubital cell of forewing partly separated by short vein, but open distally (after Kutter 1977; but Fore1 1910:29 wrote that "wing venation is absolutely the same as in other Myrmica"). Spur on tibiae of middle legs well developed and pectinate.

Type Material
Radchenko and Elmes (2003) - Material examined. Lectotype queen (upper specimen on the pin, our designation), [Switzerland] "Anzeindaz, M. myrmicoxena, Type bei M. lobicornis" (GENEVA); paralectotypes (our designation): 2 queens (middle and bottom) on the same pin as lectotype (both without postpetiole and gaster); 2 queens (one specimen without head), "Anzeindaz, 20 aout [18]69, Myrmica! mixtossima" (Sic!), "M. myrmicoxena For., Type, Anzeindaz" (GENEVA). 1 queen (with 1 worker of Myrmica lobicornis on the same pin), "lobicornis q anormale variete, parmi des w normales. Anzeindaz, Alp. Vaudoisses, 1900 metres, 20 aout", "Myrmica mymicoxena For." (GENEVA).

Etymology
Radchenko and Elmes (2010) - from the genus name Myrmica combined with xena which is derived from the Greek word xenos = guest or stranger, the name literally means “guest of Myrmica [ants]”.