Comparative Kairomonal Chemical Ecology of Diabroticite Beetles (Coleoptera: Chrysomelidae: Galerucinae: Luperini: Diabroticina) in a Reconstituted Tallgrass Prairie Ecosystem

The olfactory response to volatile semiochemicals was determined for Diabrotica undecimpunctata howardi Barber, the spotted cucumber beetle, Diabrotica virgifera virgifera Le- Conte, the western corn rootworm, Diabrotica barberi Smith & Lawrence, the northern corn rootworm, and Diabrotica cristata (Harris), a nonpest species in a tallgrass prairie ecosystem and adjacent corn and cucurbit agroecosystems in Illinois. The results indicate that the divergence in response to plant volatiles by these Diabrotica species can be correlated with currently accepted phylogenetic groupings between the virgifera and Fucata groups, as well as within the virgifera group. For example, cinnamaldehyde is most attractive to D. u. howardi (fucata group), whereas 4-methoxycinnanlaldehyde is a specific attractant for D. v. virgiferal (virgifera group). The 2 closely related species D. barberi and D. cristata (virgifera group) were both attracted to eugenol, cinnamyl alcohol, and 4-methoxyphenethanol on one or more test dates. Although D. cristata is not normally found in cucurbit blossoms, adults were attracted to traps containing shredded blossoms of Cucurbita maxima Duchesne ex Poir. Furthermore, all 4 Diabrotica species responded to a multicomponent synthetic lure (a cucurbit blossom mimic), suggesting a commonality of response to cucurbit blossom aroma. A review of the literature on Diabroticite chemical ecology suggests cucurbit volatiles acted evolutionarily as synomones, providing a primitive means of pollination for cucurbits. For several Dillbrotica species, the olfactory response to these volatiles also may have facilitated the finding of noncucurbitaceous pollen sources.