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).

Three colonies of Harpagoxenus sublaevis were found by breaking open dry pine twigs that contained Leptothorax acervorum workers and queens on the Hanko peninsular in Southern Finland during September 2012. Roughly every one in 15 colonies of L. acervorum found was parasitized.

Guillem et al. (2014) examined cuticular hydrocarbon (CHC) profiles between this parasite and its hosts. They found that the parasitic species had CHC profiles that were indistinguishable from that of their hosts. The level of chemical mimicry even extended to the more subtle between-colony differences in profiles. In all cases the profiles of un-parasitized colonies were similar to those that were parasitized indicating that it is the parasites that have adjusted their profile to match that of their host and not vice versa. This explains why these social parasites are fully integrated members of each colony and are treated as nest-mates. It also helps to explain why raiding parties of Harpagoxenus workers are frequently killed or driven off when trying to raid or invade new host L. acervorum colonies (Winter and Buschinger, 1986), since they are carrying their own host colony odour, which is likely to be different from that of the one they are raiding. This is why parasites continue to use a wide range of other chemical and morphological adaptations associated with their parasitic lifestyle. These include a thickened cuticle and production of appeasement or propaganda compounds (e.g. Allies et al., 1986; Lloyd et al., 1986; Ollett et al., 1987; D'Ettorre et al., 2000). These tactics allow the parasite time to make the necessary adjustments to its profile. Acquiring a host profile may be possible in just a few hours (R. Kather, pers. comm., cited in Guillem et al. (2014)).

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.