Eciton testaceum Schenck The Formicidae (Hymenoptera) of Fennoscandia and Denmark. Collingwood, C. A. Fauna Entomologica Scandinavica 1979 8 1 174 534S4 urn:lsid:biosci.ohio-state.edu:osuc_concepts:36558 Insecta Formicidae Strongylognathus Animalia Strongylognathus testaceus (Schenck) Hymenoptera 80 Arthropoda species testaceus  Figs. 108,109.   Eciton testaceum Schenck, 1852:117.     Figs. 106, 107. Anergates atratulus (Schenck). - 106: male in profile; 107: queen in dorsal view. Scale: 1 mm.  Figs. 108, 109. Strongylognathus testaceus (Schenck). - 108: head of worker in dorsal view; 109: head of male in dorsal view. Scale: 1 mm.    Worker. Yellowish brown. Head rectangular with pronounced occipital emargination and posterolateral angles. Body shining with long fine pale hairs present also on appendages. Sculpture variable, with longitudinal striae present or more or less effaced on head and alitrunk. Length: 2.0-3.6 mm. Queen. Darker than worker, brownish with paler appendages. Wings pale with 1 cubital cell, 1 discoidal and an open radial cell. Length: 3.5-3.8 mm. Male. Dark brown with pale brown appendages. Head small narrower than promesonotum. Occiput emarginate sharply angled postero-laterally. Antennal scape shorter than second funiculus segment. Length: 3.2-4 mm.  Distribution. Very rare in S. Sweden, only recorded from Sm. and 01. - Recorded in England from Devon, Dorset and Hants very locally. - Range: Pyrenees to Ukraine, North Italy to Sweden.  Biology. This species occurs only in the nests of its host Tetramorium caespitum. Workers and brood of both host and parasite are present but only the sexuals of Strongylognathusare developed, the original Tetramoriumqueen as well as the adoptive Strongylognathusqueen usually being found present together.  S. testaceusworkers are normally greatly outnumbered by Tetramoriumworkers. Observations on this and related species suggest that neighbouring nests of the host species are raided to recruit more Tetramoriumpupae to the colony which is often very populous with up to 20,000 individuals. Alatae are present in July and August