Formica aserva

Formica aserva is a brood raiding ant that preys on other Formica species. Within its range this species is encountered with some regularity during the summer due to its raids on other ant nests. These raids typically include an active and noticeable foraging column that can be many meters from the raiding colony to the ant nest that is being attacked. Soon to pupate brood that is brought back to the nest is often allowed to eclose and these workers become working members of the F. aserva colony.

Identification
The ventral surface of the head is without erect hairs, the pronotum has fewer than 6 short (less than 0.01 mm) stiff, blunt bristles, and the apex of the petiole is without erect hairs. The petiole is broad and fan-shaped as seen from the front. The central area of the clypeus is striate. (Mackay and Mackay 2002)

Distribution
Canada, Newfoundland west to Yukon. United States: Alaska south to California, east to New Mexico, northeast to New England.

Distribution based on Regional Taxon Lists
Nearctic Region: Canada, United States.

Habitat
For New Mexico (Mackay and Mackay 2002) - This species occurs in a wide variety of habitats, ranging from prairies, through sagebrush scrub, juniper forests (Juniperus monosperma), aspen forests (Populus tremuloides) and mixed forests up to fir-aspen-spruce forests, subalpine fir (Abies lasiocarpa) and ponderosa pine. Nests even occur above the tree line.

Biology
This species is a member of a group of Formica species that were formerly placed in the subgenus Raptiformica. All species are facultative slavemakers, i.e., species which usually or often have slaves but can get along without them. The colony-founding female forces her way into a small colony of another species of Formica, somehow gets rid of its queen and workers and appropriates its nest and brood. The workers emerging from this brood accept the intruding queen as their own. The enslaved species belong to the Formica neogagates, fusca, and pallidefulva species groups. When the workers of the slave-making species have become numerous enough, they start raiding for more slaves.

In New Mexico (Mackay and Mackay 2002): This species nests in ponderosa pine logs and under stones, and may even construct thatched nests. Brood can be found in nests in early July until early August, reproductives were in nests in August, dealate females were found loose in July and August. This species enslaves F. fusca, F. argentea and F. neorufibarbis, and was found in a F. argentea nest together with F. obtusopilosa. One mixed nest included F. argentea, F. aserva, F. obtusopilosa F. lasioides and Myrmica.

Nevada, Wheeler and Wheeler (1986) - We have 26 records from 20 localities, all near the northeastern, eastern, and southern borders of the state; 6,600-11,000 ft., with 68% above 10,000 ft. Twelve records are from the Coniferous Forest Biome and 9 from the ecotone above it. Seven nests were in and/or under decaying wood lying on the ground; usually thatch and soil were piled against or on top of the log. One nest was in needle thatch under and beside a stone. Another was in thatch and soil under a 10-cm stump 38 cm long and leaning against a huge stone. One colony was populous and aggressive. As slaves we found Formica argentea in 1 colony, Formica neorufibarbis in 1 colony, and Formica fusca in 3 colonies.

Castes

 * Worker

Nomenclature

 *  aserva. Formica sanguinea r. aserva Forel, 1901g: 395 (w.q.) CANADA. Wheeler, W.M. 1913f: 405 (m.). Combination in F. (Raptiformica): Emery, 1925b: 260. Synonym of subnuda: Creighton, 1950a: 469; Wilson & Brown, 1955: 118; Buren, 1968a: 33. [All these authors give subnuda as the senior name but the date of availability of subnuda makes it clear that aserva has seniority: Bolton, 1995b: 191; see also under subnuda.]
 * subnuda. Formica sanguinea subsp. subnuda Wheeler, W.M. 1910g: 570 (w.) CANADA. [First available use of Formica sanguinea subsp. rubicunda var. subnuda Emery, 1895c: 335; unavailable name.] Wheeler, W.M. 1913f: 409 (q.m.); Wheeler, G.C. & Wheeler, J. 1953c: 170 (l). Combination in F. (Raptiformica): Emery, 1925b: 260. Subspecies of sanguinea: Wheeler, W.M. 1913f: 469; Wheeler, W.M. 1917a: 533. Raised to species: Creighton, 1950a: 469. Synonym of aserva: Creighton, 1950a: 469; Wilson & Brown, 1955: 118; Buren, 1968a: 33. [Creighton, Wilson & Brown, and Buren incorrectly make subnuda the senior name but aserva has priority and is therefore the valid name of this taxon: Bolton, 1995b: 204.]