Wild solitary bees and their use of bee hotels in southwest Spain

Abstract

There is an increasing interest in preserving and, if possible, increasing wild bee populations as evidenced by increasinginvestigations into providing supplemental nesting resources, commonly called bee hotels. The study presented herewas carried out in 2017 and 2018 with two objectives: a) to understand the role that insect refuges could have onbeneficial arthropod fauna, especially bees, and b) to evaluate different materials and which species used them. We pre-sent the preliminary results of three constructed refuges in Seville, Spain: Hymenoptera visited the refuges most fre-quently (88.7% of the visitors), of which the social wasps (Polistes dominula(Christ)) were most common, followed bybees. Bees were observed visiting bamboo canes, Arundo canes, drilled logs, and grooved boards. Drilled logs were themost used material (31.5 and 37.6% occupied in 2017 and 2018, respectively), followed by bamboo canes (14.1 and17.4% of occupied in 2017 and 2018, respectively). For drilled logs, holes of 4.9–6.5mm (2017) and 7.0–9.2 mm (2018)were preferred, whilst diameters of 2.6/2.7–4.9/5.0 mm (both 2017 and 2018) were preferred for bamboo canes. Forgrooved boards, holes of 5.0 mm (only 2018) were preferred. The bee species most frequently nesting in bamboo caneswereCeratina cucurbitina(Rossi) andCeratina dentiventrisGerstacker, whereas in drilled logsHoplitis lepeletieri(P erez)was most common, butHoplitis adunca(Panzer) was also recorded. Their abundance throughout the study period variedbetween species, and their role in biodiversity and sustaining wild flora is discussed.