Cleptoparasitic: Hosts; In Britain the putative hosts are Osmia leaiana (F. Smith, 1845c, 1876; Morley, 1900; R.C.L. Perkins, 1923; Chambers, 1949) and possibily O.caerulescens (F. Smith, 1845c; R.C.L. Perkins, 1923). There appear to be no British rearing records of this Stelis. The descriptions of the association between this species and its possible hosts are usually restricted to accounts of the presence of the cleptoparasite in the vicinity of the nesting burrows of these species in walls and woodwork, or actually entering their burrows. Jones (1932) extracted a female from a nest burrow of O. leaiana at Wicken Fen, Cambridgeshire. There are also records from Devon of specimens flying about cob walls.
It is possible that several host species may be involved in Britain, as on the continent the following have been cited: O. leaiana (Blüthgen, 1919; Jørgensen, 1921; Crèvecoeur, 1925; Blüthgen in Schmiedeknecht, 1930; Müller, 1931; van der Zanden, 1955, 1982; Banaszak & Romasenko, 1998 and Peeters, Raemakers & Smit , 1999); O. fulviventris (Blüthgen, 1919; Jørgensen, 1921; Bischoff, 1927; Blüthgen in Schmiedeknecht, 1930; Müller, 1931; van der Zanden, 1955, 1982; Banaszak & Romasenko, 1998 and Peeters, Raemakers & Smit, 1999); O. rufa (Blüthgen in Schmiedeknecht, 1930; Banaszak & Romasenko, 1998); O. bicolor (Schenck in Blüthgen, 1919);Osmia emarginata (Banaszak & Romasenko, 1998); Osmia inermis (Banaszak & Romasenko, 1998) Hoplitis anthocopoides (Banaszak & Romasenko, 1998), H. leucomelana (Tork in Blüthgen, 1919); H. spinulosa (Gehrs, 1902; van der Zanden, 1982; Banaszak & Romasenko, 1998 and Peeters, Raemakers & Smit, 1999); Anthidium manicatum (Müller, 193l) Heriades truncorum (Möschler in Blüthgen, 1919; Jørgensen, 1921); Megachile rotundata (Banaszak & Romasenko, 1998). Clearly further clarification of these hosts based on rearing from known nests is desirable.
Stanisavljević (2000) [perhaps copying Banaszan & Romsenko, 1998) cite the following host species: Hoplitis anthocopoides, Hoplitis spinulosa, Osmia emarginata, Osmia fulviventris, Osmia leaiana, Osmia bicornis (as O. rufa), Osmia inermis, Megachile rotundata.
Celary (1989) lists Osmia fulviventris, Osmia rufa, Osmia emarginata, Osmia atrocaerulea, Osmia leaiana, Hoplitis anthocopoides, Chelostoma maxillosum and Megachile centuncularis as hosts.
Matache & Ban (2006) list: Hoplitis anthocopoides, Anthocopa spinulosa, Osmia emarginata, O. fulviventris, O. leaiana, O. rufa, Megachile rotundata.
Warncke (1992) believed that the parasitism was more or less confined to Osmia niveata and O. emarginata (although this can not be the case in Britain as neither of these species is present), and that all other rearing records were rare and sporadic. He lists Osmia rufa, O. anthocopoides, O.parietina, O. bicolor, Osmia spinulosa, Hoplitis leucomelana, Osmia loti, Heriades truncorum, Chelostoma florisomne and Anthidium manicatum as occasional hosts.