Caterpillar Footprints as Host Location Kairomones for Cotesia marginiventris: Persistence and Chemical Nature

Abstract

Herbivores walking over the epicuticular wax layer of a plant may leave tracks that disclose their presence to hunting predators or parasitoids. The braconid wasp Cotesia marginiventris is a solitary parasitoid of young noctuid caterpillars. It can locate potential hosts from a distance by orienting toward the scent of herbivore-damaged plants. Upon landing on the caterpillars' food plant, the female parasitoid searches for further cues (kairomones) that confirm the presence of a suitable host. In a previous study, we showed that C. marginiventris recognizes the chemical footprints of absent Spodoptera frugiperda caterpillars on a leaf. Here, we report on the persistence and chemical nature of this host location kairomone. In a series of behavioral assays, we confirmed that caterpillars of S. frugiperda leave chemical tracks that elicit characteristic antennation behavior in C. marginiventris for up to 2 days. Both hexane extracts of caterpillar footprints and of the larvae's ventral cuticle induced antennation and contained almost identical long-chain hydrocarbons, thus suggesting the prolegs and claspers as the kairomones' main source. A series of linear C(21) to C(32) alkanes accounted for ca 90% of all identified compounds. Female wasps showed significant antennation responses on leaves treated with a reconstructed blend of these n-alkanes. However, wasp responses were relatively weak. Therefore, we presume that minor compounds, such as monomethyl-branched alkanes, which were also found, may contribute additionally to host recognition.

Comparative GC-EAD Responses of A Specialist (Microplitis croceipes) and A Generalist (Cotesia marginiventris) Parasitoid to Cotton Volatiles Induced by Two Caterpillar Species

“…Additionally, unknown minor compounds as well as hostspecific volatiles also may play a role in differentiation of different host-plant complexes. Further discrimination may be mediated at short range by host contact kairomones (which are typically of relatively lower volatility), such as host feces (Loke and Ashley 1984;Dmoch et al 1985;Afsheen et al 2008) and caterpillar chemical footprints on infested plants (Rostas and Wölfling 2009). Future behavioral studies are necessary to confirm whether or not the ability of M. croceipes to distinguish between plants damaged by its host and non-host caterpillars (Rosé et al 1997), is in fact mediated by the subtle quantitative differences in volatile blends recorded in this study.…”

Deciphering the signature of cuticular lipids with contact sex pheromone function in a parasitic wasp

“…The non-polar CHCs have been extensively investigated over the past three decades with respect to their role as semiochemicals (Howard, 1993;Singer, 1998;Howard and Blomquist, 2005). A multitude of studies have shown that CHCs are not only involved in the diverse interactions of social insects (Greene and Gordon, 2003;Endler et al, 2004;van Zweden and d'Ettorre, 2010) but also used by many solitary insects as contact stimuli when searching for oviposition sites (Colazza et al, 2007;Rostas and Wolfling, 2009;Darrouzet et al, 2010) or sexual mates (Syvertsen et al, 1995;Sullivan, 2002;Steiner et al, 2005;Steiner et al, 2006;Sugeno et al, 2006;Geiselhardt et al, 2009;Ferveur and Cobb, 2010;Ginzel, 2010;Ruther et al, 2011).…”

Host Sex Discrimination by an Egg Parasitoid on Brassica Leaves

“…It remains to be investigated for how long T. basalis can detect the chemical footprints of its host. Studies on a larval parasitoid showed that the wasps recognize footprints from caterpillars for a period of at least 2 days (Rostás and Wölfling, 2009). This suggests that these kairomones can be retained for a relevant length of time and should help to improve the efficiency in finding a suitable host.…”

“…Smith) (Lepidoptera: Noctuidae), when footprints that mainly consist of linear and monomethyl-branched alkanes are left on the leaf surface of either wild-type or eceriferum mutants of barley. The mutants were characterized by lower amounts of the main wax component hexacosanol and a high aldehyde fraction (Rostás et al, 2008;Rostás and Wölfling, 2009).…”