Leptothorax unifasciatus

23. Leptothorax unifasciatus (Latreille, 1798) Fig. 100.

Formica unifasciatus Latreille, 1798:47.

Worker. Yellowish with the head often brown and the gaster characteristically having a dark band across the first gaster segment. The propodeal spines are short but strong and distinct. The outline of the alitrunk is more flattened than in L. interruptus and the petiole node in the worker has a distinct dorsal truncate area which meets the anterior face at a clearly defined angle. Length: 2.8-3.5 mm.

Queen. Pale brown to brownish black with distinct dark band across first gaster tergite; mesoscutellum diffusely sculptured; antennal clubs brownish, darker than rest of funiculus. Propodeal spines reduced to very short denticles; petiole more peaked than in worker. Length: 4.0-4.5 mm.

Male. Brownish black, appendages very pale; antennal scape as long as following 3 segments; space between notauli with dilute sculpture. Length: 2.8-3.5 mm.

Distribution. Very local, recorded from Sweden: Öl. only, first taken in 1968 by H. Andersson and later rediscovered among limestone ruins by P. Douwes (1976a). - The species does not occur in England but is common on the Channel Islands. - Range: an abundant species throughout Central and South Europe from Spain to the Caucasus and from South Italy to North Germany and the Netherlands.

Biology. This widely distributed and common species is rather similar to L. tuberum but is slightly larger and in the female castes easily distinguished by the banded gaster. It nests among rocks and under stones but also frequently occurs under bark. Individual colonies are usually more populous than the other North European Leptothorax species with workers numbering 200 or more. Alatae are found in July and August.