Osmia (Helicosmia) caerulescens (Linnaeus, 1758)

Polylectic, mainly visiting species in the families Asteraceae, but also Fabaceae (Lotus) and Brassicaceae (Raw, 1974) and Lamiaceae (Peeters, Raemakers & Smit, 1999; Stanisavljević, 2000).

Else & Edwards (2018) report that in the UK, the species is known to visit: Lotus corniculatus (Fabaceae); Rubus laciniatus (Rosaceae); Antirrhinum, Veronica chamaedrys (Plantaginaceae); Nepeta, Glechoma hederacea (Lamiaceae); Centaurea nigra and Crepis capillaris (Asteraceae).

In France, females forage from both Fabaceae and Lamiaceae (based on pollen analysis by Tasei, 1972), including Trifolium repens, T. pratense, Medicago sativa (Fabaceae); Clinopodium, Teucrium scorodonia, Stachys, Prunella vulgaris, Ajuga reptans, Glechoma hederacea and Lamium purpureum (Lamiaceae)

In Germany, Westrich (1989, 2018) lists the following pollen sources: Echium vulgare (Boraginaceae); Lotus corniculatus, Trifolium repens, Trifolium pratense, Medicago sativa, Melilotus alba, Onobrychis viciifolia, Vicia sepium, Vicia cracca, Coronilla varia (Fabaceae); Hypericum perforatum (Hypericaceae); Salvia pratensis, Glechoma hederacea, Ajuga reptans, Lamium album, Lamium purpureum, Prunella vulgaris, Stachys recta, Clinopodium vulgare, Teucrium scorodonia (Lamiaceae); Ranunculus acris, Ranunculus repens (Ranunculaceae).

Banaszak & Romasenko (1989) state that whilst the species is polylectic, it shows a marked prefernce for Amorpha, Coronilla, Lotus, Medicago, Caragana, Melilotus, Trifolium (Fabaceae); Ajuga, Ballota, Salvia, Stachys, Thymus and Lamium (Lamiaceae).

Rust et al (2004) cite Lotus corniculatus (Fabaceae) as a pollen forage source. Janssons (2003) lists Lobelia (Campanulaceae) as a forage source in Belgium. Mavromoustakis (1953) reports visitation to Calendula persica (Asteraceae).

Mavromoustakis (1948; 1952) reports visitation to Salvia grandiflora willeana, Nepeta troodi, Ballota nigra, Onosma fruticosum Lamiaceae and Calycotome villosa, Vicia cracca elegans, Onobrychis venosa (Fabaceae) in Cyprus.

Summarising known data, Mueller (http://blogs.ethz.ch/osmiini/palaearctic-species/osmia/helicosmia/) states that the species collects pollen nearly exclusively on Fabaceae (e.g. Coronilla, Hippocrepis, Lotus, Medicago, Melilotus, Onobrychis, Trifolium, Vicia), Lamiaceae (e.g. Ajuga, Clinopodium, Glechoma, Lamium, Prunella, Salvia, Stachys, Teucrium), Boraginaceae (e.g. Echium) and Plantaginaceae (Antirrhineae) (Raw, 1974; Tasei, 1976; Westrich, 1989; Müller, 1996b; A. Müller, based on 66 pollen samples from 55 different localities and on field observations). Westrich (1989) lists Asteraceae, Brassicaceae, Hypericum (Hypericaceae) and Ranunculus (Ranunculaceae) as additional pollen hosts. The females are equipped with a specialized pilosity on the clypeus composed of curved bristles, which are used to comb pollen from the nototribic anthers of Lamiaceae and Plantaginaceae (Antirrhineae) (Müller, 1996b).

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