Interaction between the solitary bee Chelostoma florisomne and its nest parasite Sapyga clavicornis − empty cells reduce the impact of parasites

Abstract

Summary 1. Nesting behaviour and interactions between the bee Chelostoma florisomne (L.) (Megachilidae) and its nest parasite Sapyga clavicornis (L.) (Sapygidae) were studied through continual observations of individuals and dissections of bee nests. Protection of bee offspring is based on (1) the bee’s discovery and removal of parasite eggs deposited prior to the construction of a cell closure, (2) minimising the time when fully provisioned cells might be parasitised successfully, and (3) the construction of empty cells in front of brood cells. 2. An empty cell was found in front of 64.4% of all brood cells and, if the outermost brood cell in a nest was excluded, in front of 74.3% of inner brood cells. A vestibule closure is most often constructed in front of the outermost brood cell. 3. Following oviposition, the bee made only five flights, which together lasted 6–13 min, to construct a cell closure. A cell closure does not prevent the nest parasite from oviposition inside the brood cell, however, and parasite eggs deposited through the cell closure are not detected and removed by the bee. Only an additional cell closure, i.e. the formation of an empty cell, may protect a brood cell when the bee is not in the nest. The nest parasite often oviposited through the additional cell closure but its offspring were then trapped in the empty cell and starved to death. 4. Only 5.4% of the inner brood cells that were protected by an empty cell were parasitised, compared with 28.9% of those without an anterior, empty cell; 27.4% of the empty cells contained dead parasite offspring (eggs and larvae). Thus, the empty cells provided significant protection and, combined with additional means of protection of brood cells, led to a low degree of parasitism. More than 77% of the wasp offspring died at an early stage due to intraspecific interference competition within brood cells and as result of the wasps’ oviposition into empty cells.

Effects of brood parasitism on host reproductive success: evidence from larval interactions among dung beetles

“…We can estimate that parasites reduce larval survival of Onthophagus species by 66.9% for O. merdarius and 42% for O. vacca, while the other two important causes of mortality (fungal infection and predation) caused together less than 20% mortality in these species. The proportion of mortality caused by brood parasites in O. merdarius and O. vacca is similar to those found for other scarabeid species (Rougon and Rougon 1980a), and hymenopterans (Rosenheim 1989;Munster-Swendsen and Calabuig 2000). Brood parasitism causes high host offspring mortality also in birds [Trine et al (1998) and references therein], on which high frequencies of parasitism could threaten host populations (Rothstein and Robinson 1998 ; but see Smith et al 2000).…”

Nectar Sugar Limits Larval Growth of Solitary Bees (Hymenoptera: Megachilidae)

“…First, larvae were reared in a controlled laboratory setting in the absence of predation and parasitism, such as by birds, parasitic bees, or other parasites (Munster-Swendsen and Calabuig 2000, Goodell 2003, Wcislo et al 2004). In the Þeld, faster development time may decrease the amount of time larvae are vulnerable to predation and parasitism, possibly enhancing their survival.…”

Food availability affects Osmia pumila (Hymenoptera: Megachilidae) foraging, reproduction, and brood parasitism

“…Myriad aspects of the nesting biology of solitary Hymenoptera have been interpreted as adaptations to avoid parasites (Michener 1964;Evans 1966Evans , 1977Rosenheim 1989;Wcislo et al 1993;Munster-Swendsen and Calabuig 2000). Most consideration of antiparasite behaviors has focused on fixed behaviors of species, such as the nest architecture, timing of nest excavation and provisioning, or tendency to aggregate.…”