Comparative biology of four Rhodanthidium species (Hymenoptera, Megachilidae) that nest in snail shells

Abstract

Some species of two tribes (Anthidiini and Osmiini) of the bee family Megachilidae utilize empty gastropod shells as nesting cavities. While snail-nesting Osmiini have been more frequently studied and the nesting biology of several species is well-known, much less is known about the habits of snail-nesting Anthidiini. We collected nests of four species of the genus Rhodanthidium (R. septemdentatum, R. sticticum, R. siculum and R. infuscatum) in the Czech Republic, Slovakia, Catalonia (Spain) and Sicily (Italy). We dissected these nests in the laboratory and documented their structure, pollen sources and nest associates. The four species usually choose large snail shells. All four species close their nests with a plug made of resin, sand and fragments of snail shells. However, nests of the four species can be distinguished based on the presence (R. septemdentatum, R. sticticum) or absence (R. siculum, R. infuscatum) of mineral and plant debris in the vestibular space, and the presence (R. septemdentatum, R. infuscatum) or absence (R. sticticum, R. siculum) of a resin partition between the vestibular space and the brood cell. Rhodanthidium septemdentatum, R. sticticum and R. siculum usually build a single brood cell per nest, but all R. infuscatum nests studied contained two or more cells. For three of the species (R. siculum, R. septemdentatum and R. sticticum) we confirmed overwintering in the adult stage. Contrary to R. siculum, R. septemdentatum and R. sticticum do not hide their nest shells and usually use shells under the stones or hidden in crevices within stone walls. Nest associates were very infrequent. We only found two R. sticticum nests parasitized by the chrysidid wasp Chrysura refulgens and seven nests infested with pollen mites Chaetodactylus cf. anthidii. Our pollen analyses confirm that Rhodanthidium are polylectic but show a preference for Fabaceae by R. sticticum.

The native snail shell–nesting bee Osmia conjuncta (Hymenoptera: Megachilidae) exploits a local abundance of exotic Cepaea snails (Stylommatophora: Helicidae), choosing empty shells by size, colour, and microhabitat

“…2020; Hostinska et al. 2021) and have found relatively weak preferences for shell species or size. In the present study, we found considerable size variation in shells from the one snail species.…”

“…2020; Hostinska et al. 2021). The differences among snail species in size at maturity, shape, and abundance have been implicated as potential factors in shell choice (Heneberg et al.…”

“…2020; Hostinska et al. 2021). Microhabitat and shell age since snail death are argued to affect choice; shells are argued to be less favoured if they are more exposed to predators or contain decaying flesh (Bogusch et al.…”

“…2020; Hostinska et al. 2021), whether bees choose shells based on within-species characteristics of individual shells or the microhabitat of the shell remains unknown.…”

A comparison of wild bee communities in sown flower strips and semi‐natural habitats: A pollination network approach

“…The semi‐natural habitats could be also beneficial for the diversity of wild bees by providing more nesting opportunities such as bare ground, shrubs, rocky areas etc. (Hostinská et al, 2021; Hudewenz & Klein, 2013; Scheper et al, 2015), while bees in flower strips might be dependent on nesting opportunities provided by semi‐natural habitats adjacent to the field. In such case, the presence of a diverse landscape in the vicinity of the crops may also enhance the diversity of pollinators in the flower strips (Scheper et al, 2015).…”