Reproductive efficiency of the bethylid waspCephalonomia tarsalis:the influences of spatial structure and host density

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

Bethylids attacking stored‐product pests: an overview

“…Eliopoulos et al. () demonstrated mutual interference in C. tarsalis , especially at higher densities of parasitoids. Eliopoulos et al.…”

“…The main bethylids in stored‐grain ecosystems are species of Cephalonomia , Holepyris and Laelius (Table ; Howard et al., ). Some researchers have thus conducted applied studies on how the biological characteristics of bethylids and their possible interactions with other organisms can be useful in biological treatments, although several gaps in knowledge remain (Bridwell, , ; Itoh, ; Klein & Beckage, ; Flinn, ; Klein et al., ; Flinn & Hagstrum, ; Mayhew & Heitmans, ; Lord, , ; Eliopoulos et al., , ; Cheng et al., ; Ždárková et al., ; Lim et al., ; Reichmuth et al., ; Collatz & Steidle, ; Lorenz et al., ; Amante et al., ,b). Considering bethylids as biocontrol agents is important because their hosts are widely reported as pests of crops and stored products and because bethylids are biologically different from parasitoids belonging to other families (Pérez‐Lachaud & Hardy, ).…”

“…Cephalonomia tarsalis females find their hosts by two main sensory modalities. The first is sight – the wasp has well‐developed eyes, which can help when some light is present – the second is by following chemical trails deriving from the host's food and faeces (Howard et al., ; Eliopoulos et al., ). The latter was first reported for Cephalonomia waterstoni Gahan, which is able to locate Cryptolestes ferrugineus (Stephens) following the trails laid by the beetle.…”

“…This wasp also recognizes its host by the stimuli deriving from the trails and surface of O. surinamensis larvae. Host faecal odour, which is host‐specific, is also used, and the female can discriminate areas with host activities when it detects the odour (Collatz & Steidle, ; Eliopoulos et al., ).…”

“…Much of the research on the control of pests of stored grain has recently focused on biological control, which is an important component of integrated pest management (IPM) (Flinn et al., ). This strategy is highly attractive because many pests have become resistant to the main insecticides, so new organic molecules or innovative systems to control pests need to be found (Muggleton, ; Herron, ; Muggleton et al., ; Collins et al., ; Lord, ; Goubault et al., ; Adler et al., ; Eliopoulos et al., ). Politicians and organizations such as the Food and Agriculture Organization (FAO) of the United Nations (UN), the European and Mediterranean Plant Protection Organization (EPPO), and the International Organisation for Biological and Integrated Control (IOBC) have begun in recent decades to encourage eco‐friendly solutions.…”