Omalus biaccinctus (du Buysson, 1892)

Paukkunen, Juho, Berg, Alexander, Soon, Villu, Odegaard, Frode & Rosa, Paolo, 2015, An illustrated key to the cuckoo wasps (Hymenoptera, Chrysididae) of the Nordic and Baltic countries, with description of a new species, ZooKeys 548, pp. 1-116 : 11-12

Taxon classification Animalia Hymenoptera Chrysididae

Omalus biaccinctus (du Buysson, 1892) Figs 20, 21

Ellampus biaccinctus du Buysson (in André), 1892: 152.

Omalus biaccinctus : Trautmann 1927: 41.

Diagnosis.

Length 3-5 mm. Both sexes differ from Omalus aeneus and Omalus puncticollis by having a bicoloured body (head and mesosoma violet or black, mesosoma reddish or greenish) and a dull and wrinkled mesoscutum without punctures (Fig. 20). The apical notch of T3 is also more deeply triangular (Fig. 21) than in the other two species. The colour of the mesosoma is violet in the female, but dorsally black or dark violet in the male. The metasoma is greenish, golden or reddish in the female, whereas it is greenish, rarely golden or reddish, and dorsally usually black in the male.

Distribution.

Denmark, Estonia, Finland, Latvia, Norway, Sweden. Relatively rare. - West Palearctic: from western Europe to western Asia ( Linsenmaier 1959).

Biology.

Habitat: pine forest margins and clearings, semi-open sandy areas. Occasionally found on flowers of Apiaceae and Asteraceae ( Kofler 1975, Rosa 2004). Flight period: June to August. Host: Passaloecus turionum Dahlbom, Passaloecus gracilis (Curtis) and Passaloecus eremita Kohl ( Crabronidae ) ( Lomholdt 1975, Tormos et al. 1996, Wickl 2001, our own obs.). Adults have been reared from old resin-galls of Retinea resinella (Linnaeus) ( Tortricidae ) (V. Vikberg, pers. obs.) and pieces of pine wood ( Kofler 1975) with host nests inside. The females oviposit in living aphids at the hunting site of their host, and the egg is brought into the host’s nest concealed in the aphid prey ( Winterhagen 2015). Thus, the females do not enter the nest of their host for oviposition.