Cleptoparasitic: Hosts; A cleptoparasite in Britain, and on the Continent, of Eucera longicornis and E. nigrescens (F. Smith, 1843; E. Stöckhert in Schmiedeknecht, 1930; F.K. Stöckhert, 1933; Westrich, 1989). The south Devon population referred to above associates only with E. longicornis, the Nomada females having been observed exploring the nesting burrows of this species (G.M. Spooner, pers. comm.). In this locality many specimens have been observed flying slowly over the nesting site and occasionally alighting on the ground (pers. obs.). The Nomada apparently overwinters as an adult in its natal cell as such specimens have been excavated in mid March from the nests of E. longicornis (F. Smith, 1843). Probably also on E. caspica.
Westrich, (1989) also cites Eucera interrupta as a possible host in Germany (cited in Smit, 2018)