No abstract

The parasitoid wasp Cephalonomia tarsalis (Ashmead) (Hymenoptera: Bethylidae) is 23 commonly present in stored product facilities. While beneficial, it does not provide a high 24 degree of biological pest control against its host, the saw-toothed beetle Oryzaephilus 25 surinamensis (L.) (Coleoptera: Silvanidae). A candidate explanation for poor host population 26 suppression is that adult females interfere with each other's foraging and reproductive 27 behavior. We used simple laboratory microcosms to evaluate such mutual interference in 28 terms of its overall effects on offspring production. We varied the density of the hosts and 29 also the spatial structure of the environment, via the extent of population sub-division and the 30 provision of different substrates. Production of C. tarsalis offspring was positively influenced 31 by host density and by the isolation of females. With incomplete sub-division within 32 microcosms offspring production was, in contrast, low and even zero. The provision of 33 corrugated paper as a substrate enhanced offspring production and partially mitigated the 34 effects of mutual interference. We recommend simple improvements to mass rearing practice 35 and identify promising areas for further behavioral and chemical studies towards a better 36 understanding of the mechanisms of mutual interference. 37 38