Anergates atratulus

26. Anergates atratulus (Schenck, 1852)

Figs. 106,107.

Myrmica atratula Schenck, 1852:91.

Queen. Blackish brown with yellow appendages and mandibles. Mandibles reduced with single apical tooth. Palp formula 1:1, palps reduced. Clypeus with anterior margin broadly incised. Antennae 10 or 11 segmented. Eyes large, set median laterally; ocelli present. Fore-wings with 1 discoidal cell and open radial cell. Petiole transverse, postpetiole twice as broad as long, broadly attached to gaster. Gaster with longitudinal furrow in virgin queens, strongly physogastric in mature queens. Length: 2.5 mm.

Male. Pupoidal and apterous, dull pale grey. Mandibles lobiform, edentate. Antennae10 or 11 segmented; ocelli present. Clypeus with anterior margin incised. Alitrunk with flight sclerites but wings never developed. Petiole and postpetiole compressed and broadly attached to following segments. Apex of gaster reflexed ventrally. Genitalia large and prominent. Length: 2.3 mm.

Distribution. Rare in Denmark and South Sweden, recorded only from NEZ, B, Hall., Ol. and Gtl. - In England recorded locally from Devon, Dorset, Hants and Surrey. - Range: Spain to Central Siberia, North Italy to South Sweden, also North America.

Biology. This is an obligate parasite of Tetramorium caespitum. Queens fertilised within the nest of the host species fly away to secure adoption in other colonies. Queens of the host species are not present in Anergates-Tetramorium nests and only Anergates brood are developed, often in large numbers, from the single adopted Anergates queen whose gaster becomes grossly swollen.