Myrmica hirsuta

In Central Europe M. hirsuta is clearly and obligatory social parasite of Myrmica sabuleti. It produces workers only very rarely: three entire host colonies of M. sabuleti from Denmark were collected and examined yielding only 3 M. hirsuta workers. It is probable that if host colonies for other related social parasites, such as Myrmica laurae, were exhaustively searched in the same way, a few workers of these species might be located. Its nearest relative, Myrmica bibikoffi, has been recorded as free living. So, these species might illustrate trend from temporary social parasitism and facultative social parasitism (with some workers) in certain ecological conditions, to obligatory social parasitism with just a few workers being produced in some conditions. In northern Europe, M. hirsuta has been found living in Myrmica lonae colonies. This could indicate a degree of host transference but equally might indicate that M. lonae is only an "ecological race" of M. sabuleti. In our experience M. hirsuta occurs wherever a strong population of M. sabuleti exists, but on average only about 1 in 50-100 host colonies are infested (Elmes 1983). Thus one has to examine a large number of host colonies before finding M. hirsuta; generally this is easier when the host lives under stones. (Radchenko and Elmes 2003)

Identification
Similar to a microgyne Myrmica sabuleti but distinguished by the laterally enlarged post petiole, wider frons and excessive development of body hairs. Head width: 1.05 mm. Body length: 5.2 mm. Mean postpetiole width: 0.675 mm. (Collingwood 1979)

M. hirsuta is generally most similar to Myrmica bibikoffi while the queens are superficially similar to Myrmica laurae. (Radchenko and Elmes 2003)

Distribution
Very widely distributed throughout Western Europe and also found in southern England.

Distribution based on Regional Taxon Lists
Palaearctic Region: Austria, Belgium, Croatia, Czech Republic, Denmark, Finland, Germany, Greece, Hungary, Netherlands, Poland, Russian Federation, Serbia, Slovakia, Sweden, United Kingdom of Great Britain and Northern Ireland.

Biology
When Elmes (1978) described M. hirsute from southern England, he considered it to be a workerless social parasite of Myrmica sabuleti. Later, in infested nests from Denmark he found two workers (Elmes 1994), both are pseudogyne, having minute ocelli and at least a trace of scutum.

Fennoscandia, Denmark and the British Isles
Collingwood (1979) - This species was discovered by Elmes (1978) in a small group of colonies containing apparently normal Myrmica sabuleti workers and in some cases normal queens. The small queens were at first assumed to be microgynes of M. sabuleti but body pilosity and relative postpetiole measurements were found to be outside the range of that species. In size and appearance M. hirsuta resembles Myrmica myrmicoxena Forel found once only as a parasite of Myrmica lobicornis in Switzerland and also has affinities with the similar but much larger Myrmica bibikoffi Kutter (1963).

Castes
Queens and males are commonly present. Workers are relatively rare in this social parasite.

Nomenclature

 *  hirsuta. Myrmica hirsuta Elmes, 1978: 131, fig. 2 (q.m.) GREAT BRITAIN. Elmes, 1994: 439 (w.). See also: Collingwood, 1979: 51; Bolton, 1988a: 4; Radchenko & Elmes, 2003a: 228; Radchenko & Elmes, 2010: 149.

Worker
Radchenko and Elmes (2003) - (n=3): HL 1.02-1.06; HW 0.88-0.95; SL 0.78-0.80; AL 1.46-1.56 mm; FI 0.40-0.42; FLT 1.17-1.23; SI1 0.75-0.78; SI2 0.84-0.91; PPI 0.55-0.58; ESLI 0.34-0.37; queens (n=36, paratypes): HL 1.00-1.18; HW 0.88-1.10; SL 0.72-0.88; AL 1.62-2.00 mm; FI 0.39-0.46; FLI 1.10-1.30; SI1 0.68-0.81; SI2 0.73-0.84; PPI 0.57-0.72; ESLI 0.24-0.36; males (n=21, paratypes): HL 0.82-0.94; HW 0.80-0.88; SL 0.43-0.50; AL 1.66-1.92 mm; SI1 0.50-0.58; SI2 0.52-0.63; PPI 0.63-0.73; ESLI 0.06-0.12.