Harpagoxenus sublaevis

This species is a slave-maker. In Russia (Zryanin & Zryanina, 2007) it is associated with and  in boreal regions. It is also known to enslave (Guillem et al., 2014).

Identification
Pale yellowish brown to brown; head large, rectangular, with weakly concave occiput. Frontal carinae extend backward to enclose whole length of antennal scape. Antennae 11 segmented with intermediate segments strongly transverse and enlarged 4 segmented club. Eyes large, set midway at sides of head. Mesopropodeal furrow deep and distinct; propodeal spines broad and short. Femora and tibiae short and broadly rounded. Head and mesopropodeum longitudinally striate, petiole nodes and gaster smooth and shining. Whole body and appendages covered with long, acute, pale hairs. Length: 3.5-5.5 mm (Collingwood 1979).

Distribution
Pyrenees to Caucasus; northern Italy to northern Norway (Collingwood 1979); China (Xu, 2012).

Distribution based on Regional Taxon Lists
Palaearctic Region: Austria, Belarus, Belgium, Bulgaria, China, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Iberian Peninsula, Italy, Lithuania, Netherlands, Norway, Poland, Romania, Russian Federation, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine.

Biology
Workers are unable to forage outside the nest and are not capable of brood tending or feeding themselves. Host species workers (slaves) are needed for the continuation of the colony. In mixed colonies no host queen can survive, though unmated gynes of the host species frequently develop from raided pupae. They dealate and serve as slaves. Host brood is commonly not devoured. During raids, host species eggs are even discarded outside the host nest and are not carried to the slavemaker nest.

Harpagoxenus sublaevis is a species with queen polymorphism. Most functional queens are wingless ergatoid queens that usually look like large workers; alate queens are very rare and seem absent in northern parts of the range. A genetical mechanism is claimed to underlie this queen polymorphism.

Collingwood (1979) - In Denmark and Fennoscandia nests containing host species and inquiline are commonly found in twigs on the ground, tree stumps or under bark but in the mountains of Central Europe they occur rarely under stones.

Guillem et al., 2014 - H. sublaevis is a slave-maker, invading Leptothorax host colonies, killing the queen and enslaving the host workers. Since the parasite workers are not adapted to forage, killing the host queen means that the parasite workers need to raid neighbouring host colonies to replenish the slaves. Harpagoxenus sublaevis co-exists with three species of Leptothorax, Leptothorax acervorum, Leptothorax muscorum and Leptothorax gredleri, although the former is the most commonly recorded host. Colonies can also consist of mixed Leptothorax spp. slaves (Bauer et al., 2010).

Nomenclature

 * hirtula. Myrmica hirtula Nylander, 1849: 45 (w.) FINLAND. Combination in Harpagoxenus: Emery, 1924d: 266. Junior synonym of sublaevis: Mayr, 1861: 56; Dalla Torre, 1893: 64. Revived from synonymy as subspecies of sublaevis: Emery, 1924d: 266; Stitz, 1939: 154. Junior synonym of sublaevis: Radchenko, 2007: 32.
 *  sublaevis. Myrmica sublaevis Nylander, 1849: 33 (w.) FINLAND. Adlerz, 1896: 62 (q.m.); Viehmeyer, 1906: 58 (q.m.); Wheeler, G.C. & Wheeler, J. 1955b: 27 (l.). Combination in Tomognathus: Mayr, 1861: 56; in Harpagoxenus: Forel, 1893a: 167. Senior synonym of hirtula: Radchenko, 2007: 32. See also: Stitz, 1939: 151; Kutter, 1977c: 146; Buschinger, 1981: 211. Current subspecies: nominal plus caucasicus.