How can cleptoparasitic drosophilid flies emerge from the closed brood cells of the red Mason bee?

Abstract

Abstract. Aculeate Hymenoptera provision their progeny with large amounts of food. To protect their investment against brood parasites, females of many bee and wasp species construct brood cells that are hard to penetrate when finally sealed. However, the sealed brood cells also pose a problem for parasites that oviposit in the brood cell during provisioning. Brood parasites are smaller than their host and may lack strong mandibles to break through the solid brood cell walls. Furthermore, in nests built in existing cavities, newly-eclosed brood parasites need information about the location of the nest entrance. In the present study, the mechanisms of emergence are investigated in Cacoxenus indagator Loew (Diptera, Drosophilidae), the major cleptoparasite in nests of the red Mason bee Osmia bicornis L. (Hymenoptera, Megachilidae). Larvae of C. indagator move to brood cells closer to the nest entrance and sometimes make small emergence holes in the final closure of the nest entrance. Nevertheless, approximately one-third of newly-eclosed flies orientate and break through at least one intact cell partition to emerge. Flies make most of their attempts to emerge at the correct side (i.e. the one pointing to the nest entrance, probably by using the shape of the cell partition as a cue). Newly-eclosed flies use their head blister (ptilinum) to exert hydraulic pressure on particles of the cell partitions and produce small holes. Thus, C. indagator exhibits a set of behavioural and physiological adaptations enabling them to successfully emerge even from closed brood cells of their host.

Susceptibility of Red Mason Bee Larvae to Bacterial Threats Due to Microbiome Exchange with Imported Pollen Provisions

“…This indicates that the soil can sustain its natural microbiome in the bee nest independent of the health of the larvae. Therefore, apart from protection against intruders [ 9 ], its use as a nest construction element could also provide protection against pathogen spillover between the chambers of individual larvae.…”

“…The decline in solitary bee populations raises concerns regarding the environmental pressures they face [4][5][6]. Most studies on possible threats against bees focused on perils caused by increasing land-use intensity, Insects 2020, 11, 373 2 of 14 landscape fragmentation, parasites, or climate change [7][8][9]. Studies on honey bees revealed bacterial agents which can cause acute mortality in the hive [10].…”

Exposure of Larvae of the Solitary Bee Osmia bicornis to the Honey Bee Pathogen Nosema ceranae Affects Life History

“…O. bicornis is a common solitary wild bee species in Germany with a univoltine lifestyle and a flight period from March to June. The species uses wood cavities or crevices in buildings for nesting [58,59]. O. bicornis is polylectic and favors pollen resources close to the nest site [60,61].…”

Selective interspecific information use in the nest choice of solitary bees

“…Brood cell parasitism is common in cavity-nesting megachilid bees and involves high fitness costs (Krombein, 1967). Several generalist parasite species using cavitynesting bees as hosts leave an observable exit hole when leaving the host nest (Krombein, 1967;Strohm, 2011). Thus, natural selection should favour bees that recognize the hallmarks of nest healthiness and prefer nesting near healthy nests and avoid proximity to parasitized nests of others or reject abstract contextual cues that are linked to parasitization (Boyd & Richerson, 1985;Henrich & Gil-White, 2001;Laland, 2004;Sarabian et al, 2018;Litman, 2019).…”