Leptothorax tuberum

22. Leptothorax tuberum (Fabricius, 1775) Figs. 99, 101.

Formica tuberum Fabricius, 1775:393.

Workers. Colour varies from entirely pale yellowish brown with the head pale to almost black and the dorsum of the gaster brownish. The antennal clubs are brown to brownish black contrasting with the rest of the funiculus. The head and clypeus are longitudinally striate and the alitrunk rugose. The petiole node has a distinct but short truncate dorsal area; propodeal spines are very short but quite distinct. Length: 2.3-3.4 mm.

Queen. Brown to brownish black with scutellum striate throughout, rest as worker. Length: 3.7-4.5 mm.

Male. Brownish black; appendages very pale; antennal scape as long as 4 following segments. Space between notauli rugulose. Length: 2.5-3.2 mm.

Distribution. Common in South Norway, Sweden and Finland north to about latitude 62°, local in Denmark and in the coastal counties of S. England. - Range: a common and very widely distributed species in the mountains of Central Europe from Spain to the Caucasus and North Italy to Central Sweden.

Biology. This species characteristically nests in small single queened colonies under stones and in rock crevices. In Scandinavia it is restricted to warm lowland habitats. The alatae are found in July and August.

Note. The original and very brief description was based on Swedish material but the types are lost. Most Scandinavian samples have dark heads and could be referred to the supposed species L. nigriceps Mayr, 1855. In England where L. tuberum is locally abundant along the south coast, the colour tends to be uniformly pale but samples also occur with dark heads and there are no structural differences between dark headed and light coloured series.