From nest to parasite: investigating the biology and host–parasite dynamics of <i>Hoplitis laevifrons</i> and <i>Chrysis rufitarsis</i>

Hoplitis laevifrons (Morawitz) is a groundnesting solitary bee species of the subgenus Pentadentosmia, with limited knowledge regarding its nesting biology, floral preferences, and parasitoids associations. This study investigates the nesting behaviour and host–parasite dynamics of H. laevifrons and its brood parasite Chrysis rufitarsis Brullè, through observations at nesting aggregations in central Italy. Nest structure, brood cell morphology, and floral resource preferences were documented, with pollen analyses confirming oligolecty for Fabaceae. The presence of C. rufitarsis at H. laevifrons nests is published for the first time, and molecular analyses revealed the occurrence of multiple bee-attributed pathogens, especially deformed wing virus (DWV) and Nosema ceranae, in both host and parasite populations. These findings provide new insights into the nesting ecology of H. laevifrons and its brood parasite C. rufitarsis, particularly regarding pathogen transmission within wild bee communities, and highlight the need for further research on this wild bee species.