Lasius umbratus (Nylander, 1846)

BELGIUM: • 1 dealate gyne; N51.197° E4.463°; v/2020; J. Jacobs leg.; coll. RBINS; pitfall trap; W. Dekoninck det. • 1 dealate gyne; N51.169° E4.394°; vi/2020; J. Jacobs leg.; coll. RBINS; pitfall trap; W. Dekoninck det. • 1 dealate gyne; N51.205° E4.399°; viii/2020; J. Jacobs leg.; coll. RBINS; pitfall trap; W. Dekoninck det. • 1 dealate gyne; N51.125° E4.260°; ix/2020; J. Jacobs leg.; coll. RBINS; pitfall trap; W. Dekoninck det. • 1 dealate gyne; N51.199° E4.459°; viii/2021; J. Jacobs leg.; coll. RBINS; pitfall trap; W. Dekoninck det. • 1 dealate gyne; N51.135° E4.241°; viii/2021; J. Jacobs leg.; coll. RBINS; pitfall trap; W. Dekoninck det. [6 occ. (2 years), 6 roofs]

Remarks:

Only dealate gynes of this species were found and not a single worker. These gynes are probaly collected shortly after their nuptial flight when foraging to find a Lasius s. str. nest to parasitize (temporary), most likely Lasius niger . The lack of workers during this sampling campaign indicates that settlement by L. umbratus was so far not successful on the sampled green roofs. Probably this species and other Chthonolasius spp. have no options to settle on these roofs. After the temporary parasitic phase they normally prefer to make nests that are situated deep in the ground where they tend aphids on roots of grasses and/or herbs with rosettes.