D3039: Comparison of the role of host cuticular cues in host recognition and acceptance between specialist and generalist parasitoids

Parasitoids are known to use various cues to identify their suitable hosts in a complex environment. Long-range cues, herbivore-induced plant volatiles (HIPVs), are utilized for host habitat location whereas host-related cues are critical short-range cues in the later phase of the host location. Meanwhile, foraging females are likely to encounter non-host caterpillars on plants. Therefore, cues that are perceivable at a very short range become crucial to ensure oviposition in a suitable host and host cuticular hydrocarbon may act as a chemical signal in host identification. The goal of this study was to determine the role of the host caterpillar’s cuticular hydrocarbons as short-range cues in mediating successful host recognition and acceptance by parasitoids. We hypothesized that host caterpillars of specialist parasitoid have similar cuticular hydrocarbons but are different from a non-host caterpillar. The specialist endoparasitoid, Microplitis croceipes, and generalist endoparasitoid Cotesia marginiventris were evaluated against three caterpillars- Helicoverpa zea, Heliothis virescens, and Spodoptera exigua. The hydrocarbon profiles were characterized through gas-chromatography-mass spectrometry (GC-MS) and the interspecific variation in the caterpillar cuticular emissions were analyzed. We found majority of compounds were shared between H. virescens and H zea whereas it was qualitatively different in S. exigua. Additional analysis using gas-chromatography- electroantennogram detection (GC-EAD) will be conducted to unravel chemical compounds in the cuticular extract that mediate host recognition in parasitoids to explain the differences in host acceptance behavior of specialist and generalist parasitoids. The ecological and evolutionary significance of the results will also be discussed.