Leptothorax acervorum

Collingwood, C. A., 1979, The Formicidae (Hymenoptera) of Fennoscandia and Denmark., Fauna Entomologica Scandinavica 8, pp. 1-174 : 70-72

17. Leptothorax acervorum (Fabricius, 1793)

Fig. 92.

Formica acervorum Fabricius , 1793:358.

Worker. Reddish to brownish yellow with the head, antennal club and dorsal surface of gaster darker. Dorsa of petiole nodes and femora frequently infuscated. Antennae with eleven segments. Head longitudinally striate, alitrunk rugose and gaster smooth. Propodeal spines strong. Mesopropodeal suture distinct and depressed. Tibiae and scapes with numerous erect hairs. Length: 3.8-4.5 mm.

Queen. As worker but darker sometimes almost black. Length: 3.8-4.8 mm.

Male. Brownish black, large and robust; antennae 12 segmented with very short scape; semi-erect hairs numerous on tibiae. Length: 4.5-5.0 mm.

Distribution. Abundant throughout Denmark, Fennoscandia and British Isles. - Range: northernmost Scandinavia to mountains of South Europe and from Spain to Japan.

Biology. This species nests in small isolated colonies of 25 to 60 individuals with one or several queens; worker-queen intercastes are frequent. It is found nesting in open moorland in peat, rock crevices and under stones and in woodland areas on fallen tree trunks, rotten branches, stumps or under bark. The workers forage singly, predating small insects or scavenging insect corpses. It has not been observed to tend aphids, is non-aggressive and avoids combat with other ants. Alatae occur in the nests in June and July and have been observed flying and mating on high ground in July.

Note. This is a comparatively large and robust species easily recognised by the abundant suberect appendage hairs in all castes. The species tends to darken in colour from south to north varying from bright yellowish brown to nearly black, the darker samples occurring chiefly in high mountain areas, peat bogs and in the arctic north but with no clear break in colour gradation to the dark form sometimes referred to as the variety nigrescens Ruzsky (1905).