Tetramorium caespitum

28. Tetramorium caespitum (Linne, 1758)

Figs. 2, 110-112.

Formica caespitum Linne, 1758:581.

Worker. Blackish brown, sometimes paler; head including clypeus and alitrunk regularly longitudinally striate. Petiole and postpetiole with shallow punctures and sculpture but smooth in centre. Propodeal spines very short, broadly denticulate, petiole and postpetiole about as broad as long. Length: 2.5-4 mm.

Queen. Blackish brown with appendages and mandibles paler. Pronotum concealed above by overarching mesonotum. Mesonotum and scutellum smooth and shining. Much larger than worker with petiole and postpetiole broadly transverse. Wings pale with 1 discoidal and 1 cubital cell and open radial cell; pterostigma and veins yellowish. Length: 6-8.0 mm.

Male. Head much narrower than alitrunk, rounded with very large eyes; antennal scape shorter than second funiculus segment. Y-shaped notauli and parapsidal furrows distinct. Postpetiole much wider than long. Head, propodeum, petiole and postpetiole longitudinally striate, mid body more finely striate. Size much larger than worker. Length: 5.5-7 mm.

Distribution. Locally common in Denmark and Southern Fennoscandia up to approximately latitude 62° 50'. - Range: holarctic: America to Japan, North Africa to N. Europe including British Isles.

Biology. The species tends to be coastal in North Europe but also inland on heath and on the open borders of woodland, nesting in the earth and also under stones. Colonies are normally single queened, but populous with up to 10,000 or more workers. This species is moderately aggressive, living by predation on other arthropods, scavenging and also from root aphid honeydew. Seeds of various herbs and grasses are often collected into the nest. The alatae are conspicuously large compared with the workers; they are developed in the early summer and fly in late June and July. prolonged backward; propodeal spines long. Length of worker: 3.4-4 mm, queen: 5-5.5 mm.

Male. Yellow brown to brown; mesonotum and postpetiole shining, rest of alitrunk and head weakly sculptured; frontal carinae prolonged backward; occiput bluntly angled at posterolateral borders; propodeum with 2 short spines. Length: 4.5-5 mm.

Biology. This is a cosmopolitan species of tropical origin often introduced and established in heated glasshouses in the British Isles. It nests in small communities in earth, under bark and in or on shrubby hothouse plants. Long know as Tetramorium guineense (Fabricius), Bolton (1977) has shown that the correct name is T. bicarinatum.