An illustrated key to the cuckoo wasps (Hymenoptera, Chrysididae) of the Nordic and Baltic countries, with description of a new species Author Paukkunen, Juho Author Berg, Alexander Author Soon, Villu Author Odegaard, Frode Author Rosa, Paolo text ZooKeys 2015 548 1 116 http://dx.doi.org/10.3897/zookeys.548.6164 journal article http://dx.doi.org/10.3897/zookeys.548.6164 1313-2970-548-1 D5D7B51E5AC6460D9B3C7584E46F9B3F D5D7B51E5AC6460D9B3C7584E46F9B3F Taxon classification Animalia Hymenoptera Chrysididae Chrysis impressa Schenck, 1856 Figs 10, 84, 85, 92, 107, 108, 116, 132, 149, 164, 168, 170, 177 Chrysis impressa Schenck, 1856: 29. Chrysis ignita var. aurifera Linsenmaier, 1951: 76. Diagnosis. Length 6-11 mm. The species is easily confused with other similarly coloured species of the Chrysis ignita group and a combination of different diagnostic characters should be used in species determination. The head and the mesosoma are dorsally dark blue or black, and in the female the pronotum, mesopleuron and mesoscutellum have extensive golden green reflections (Fig. 164). The mesoscutum of the female is characteristically black, dark grey or olive coloured with contrastingly green or blue punctures (similar to Chrysis longula ) (Fig. 164). The mesoscutum of the male is often entirely dark blue or blue-violet. The tergites are golden red and relatively finely punctured (Figs 107, 108). The sternites are at least partially red-golden (Figs 116, 132) and the black spots of S2 are usually roundish in the female (Figs 116). The setae on the dorsal surface of the head are brownish in both sexes (Fig. 149). The mandible is relatively thick (medial width about half or nearly half of basal width) and basally with only slightly concave margins (Figs 141, 149). F1 is long and narrow, about 1.4 times as long as F2 in the female and at least 1.2 times as long as F2 in the male (Fig. 177). Distribution. Denmark, Estonia, Finland, Latvia, Lithuania, Norway, Sweden. Very common. - West Palearctic: from western Europe to central Asia ( Linsenmaier 1997 ). Biology. Habitat: forest margins, clearings and gardens with sun-exposed dead wood. Adults are mainly observed flying and running on walls of wooden buildings (e.g. log barns), dead tree trunks (e.g. Betula , Populus ), poles and log piles. Flight period: early June to late August. Host: Mainly Ancistrocerus claripennis Thomson and Ancistrocerus parietinus (Linnaeus) ( Paern et al. 2014 , Martynova and Fateryga 2015 , our own obs.), but probably also Ancistrocerus trifasciatus ( Mueller ) ( Vespidae ) ( Morgan 1984 , Paern et al. 2014 , our own obs.).