Myrmica luteola

Radchenko and Elmes (2003) - There are very few published accounts of the biology of this unusual Myrmica species. Kupyanskaya (1990) described how, in Far Eastern Russia, M. luteola usually lives in open places in spruce and southern-type mixed forest, generally preferring forest glades and the meadows bordering rivers and lakes; she noted that it usually builds its nests in decaying wood and that sexuals are present in the nest from June-September. In Japan, M. luteola inhabits sparsely forested rocky sites and builds nests under stones or around tree roots; nuptial flight take place from September to mid-October (Masuko and Terayama 2002).

Identification
Queens of this species are not very obvious being hardly larger, or even somewhat smaller, than their workers. The queen differs from her workers by an absence of propodeal spines (or at most with short denticles), while the workers have long propodeal spines. Although some reduction of the propodeal spines in relation to those of workers is not unusual for queens, the reduction shown by M. luteola is unique for all other known Myrmica species. M. luteola also possess several "socially-parasitic" features, such as reduced spurs on mid- and hind tibiae, slightly developed ventral petiolar and postpetiolar processes and a very hairy body. In addition, the first gastral tergite of workers and queens is distinctly longitudinally-striated basally; this unusual feature for Palaearctic Myrmica is known only from the Nearctic Myrmica striolagaster. (Radchenko and Elmes 2003)

Distribution
Southern part of the Russian Far East, NE China, Korean Peninsula and Japan.

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan. Palaearctic Region: Democratic Peoples Republic of Korea, Russian Federation.

Biology
Radchenko and Elmes (2010) - M. luteola is widespread throughout temperate East Asia but seems to be rare throughout its distribution. It inhabits spruce and southern-type, warm mixed forest, where it prefers glades and the meadows bordering rivers and lakes; the highest altitude recorded for the habitats of this species is 1820 m a.s.l. in North Korea (Radchenko 2005). In the Russian Far East, nests were found in tree logs and stumps, but in Korea and Japan, they also were built in soil, often under stones or around tree roots. Sexuals are present in the nest from June to September, in Japan the nuptial flight take place from September to mid-October (see also Kupyanskaya 1990; Imai et al. 2003; Radchenko 2005).

Based entirely on morphological characteristics, we speculated that M. luteola might be at least a temporary social parasitic microgyne form, derived from a species such as Myrmica mirabilis (Elmes and Radchenko 1998, 2003a). Recently Masuko and Terayama (2002) showed that M. luteola might be temporary social parasite on Manica yessensis Azuma; if they are correct then M. luteola would be the first example, of intergeneric parasitism by a Myrmica species. This is not implausible as there seems to be a tendency for social parasites to use less related hosts the older the species is in geological time (see Jansen et al. 2010). On the other hand, it seems unlikely because the Japanese evidence is open to several other interpretations and there are no Manica species in the Russian Far East, Korea and China. Thus over most of its range M. luteola must either parasitize a different host or it establishes its nests independently. This interesting “old” species deserves more study.

M. luteola is quite unusual compared to most other Myrmica species and well differs from any other known member of the genus; this led Radchenko (1994a) to define the separate, luteola species group. This idea was recently supported by the moleculargenetic phylogeny produced by Jansen et al. (2010): M. luteola formed a separate clade that probably had a common ancestor with the ritae-group of species > 25 Ma, which indicates that it is indeed a relic of an ancient Myrmica fauna.

M. luteola has many features of the so-called “inquiline syndrome” (see Wilson 1971, 1984), i.e. strongly reduced and simple non-pedtinate spurs on the middle and hind tibiae, somewhat developed ventral petiolar and postpetiolar processes, a hairy body and especially very small queens, which are even smaller than the workers. Moreover, uniquely for the genus, the queens have no propodeal spines, the propodeum being only angled with at most very short blunt denticles. Additionally, the workers and queens show another feature that very rarely occurs in Myrmica species: the first gastral tergite is distinctly longitudinally striated basally.

Nomenclature

 *  luteola. Myrmica luteola Kupyanskaya, 1990: 103, Figs. 16, 17 (w.q.) RUSSIA. Radchenko, 1994f: 75 (m.). See also: Masuko & Terayama, 2002: 228; Radchenko & Elmes, 2003a: 239; Radchenko & Elmes, 2010: 197.

Etymology
Radchenko and Elmes (2010) - named from the Latin diminutive adjective luteola = yellowish; for the colour of the workers.