Formica suecica Adlerz

54. Formica suecica Adlerz, 1902 Figs. 203,209,213,218.

Formica suecica Adlerz, 1902: 263.

Worker. Alitrunk and head reddish, ocellar region often indistinctly brownish; gaster brown with basal face reddish. Head broad with rounded sides and occipital corners which round gently into shallow posterior emargination. Scale with rounded dorso-lateral angles and flat central emargination. Palpi six segmented, short not extending beyond front eye margin. Scattered hairs on clypeus, frons and dorsum of all gaster tergites. Eyes without hairs. Length: 4.5-6.5 mm.

Queen. Brownish black with only propodeum paler reddish brown. Head broad with sides and occipital angles broadly rounded. Scale with distinct dorso-lateral lobes. Eyes bare. Length: 5.5-6.3 mm.

Male. Dark brown, legs and genitalia pale brown. Head broadly rounded, scarcely emarginate posteriorly; dorsal surfaces with scattered erect hairs; eyes bare. Maxillary palps moderately long, 6 segmented. Length: 6.0-7.0 mm.

Distribution. Not in Denmark. - Sweden: generally distributed from Sm. north to Lu. Lpm., but not recorded from 01., Gtl. and G. Sand. - Norway: HE, VE, R and SF. - Finland: Ab, N, Om, ObS and ObN. - Range: Fennoscandia and Esthonia only.

Biology. This is a truly endemic Fennoscandian species, not recorded east of longitude 30° or south of latitude 56°. Nests are in open sites in tree stumps with scattered leaf litter but not piled up into a dome. This species may be confused with the redder examples of F. exsecta but is easily distinguished by the broadly rounded head and bare eyes. Males and queens occur in July and the small queens start fresh colonies by adoption by either F. fusca or less commonly F. transkaucasica. The habits of F. suecica have been studied by Adlerz (1902) on the offshore island of Alno in Central Sweden where many nests were found, by Holgersen (1943) in Norway and by Forsslund (1947).