Consequences of Parasitized Prey Provision on the Fitness and Development Parameters of a Solitary Wasp, Rhynchium brunneum brunneum (Vespidae: Eumeninae)

Abstract

The solitary wasp, Rhynchium brunneum brunneum (Fabricius), constructs nests in hollow cavities of bamboo, provisions her brood cells with caterpillars, and partitions the cells using mud. The wasp larva, upon hatching, feeds on the provisioned lepidopteran larvae and completes its development inside the cell. The fitness and development of immature stages of the wasp on the prey parasitized by Dolichogenidea sp. (Braconidae: Microgastrinae) was studied. The number of cells with parasitized prey was significantly higher during September (6.60 ± 0.11 parasitized prey/cell), October (9.20 ± 2.77 parasitized prey/cell), November (9.10 ± 2.59 parasitized prey/cell), and December (9.00 ± 2.01 parasitized prey/cell). The percentage of healthy prey per cell ranged between 53.33% to 100%, and parasitized prey per cell ranged from 0 to 25% in the sampled nests. The mortality of late instar wasp larvae (50 to 80%) was higher in the cells provisioned with the parasitized prey. The number of prey larvae provisioned per cell was significantly higher in the healthy cells (9.80 ± 0.84 prey/cell) compared to the unhealthy cells (3.60 ± 0.55 prey/cell). The prey biomass in the healthy cells (0.592 g) was significantly higher than in the unhealthy cells (0.161 g). The emergence percentage of the adults was significantly higher in the healthy nests (100%) than in unhealthy nests (38.67%). The study confirms the inability of the adult wasp to discriminate between healthy and parasitized prey. The adult wasp compensated for the fitness of her immature stages by collecting a mixture of healthy prey with parasitized prey to favor the growth and development of her broods in the nest.