Olfactory reactions of the twelve-spotted lady beetle, Coleomegilla maculata and the green lacewing, Chrysoperla carnea to semiochemicals released from their prey and host plant: Electroantennogram and behavioral responses

Electroantennograms (EAGs) were recorded from two predatory insect species, the twelve-spotted lady beetle, Coleomegilla maculata and the green lacewing, Chrysoperla carnea in response to semiochemicals emitted from one of their prey species, the pea aphid Acyrthosiphon pisum and their host plant. EAG responses were also recorded from C. maculata in response to extracts from individuals of the opposite sex and to extracts from an herbaceous plant, catnip Nepeta cataria. Extracts of catnip and two sex pheromone components of aphids, (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol, elicited significant EAG responses from the antennae of both predatory species. Of 10 corn volatile compounds tested, C. carnea adults responded most strongly to 2-phenylethanol and (E)-β- farnesene. A significant difference in EAG response to extracts of corn leaf collections was observed between male and female C. carnea. In C. maculata, significant EAG responses were elicited by most of the tested corn volatile compounds, except α-pinene and (E)-2-hexenal. The highest EAG responses were observed in response to (E)-β-farnesene, α-terpineol, 2-phenylethanol, and β-caryophyllene. Sexual differences in EAG responses of C. maculata were only found in response to 1-octen-3-ol. Male antennae of C. maculata produced significant EAG responses to extracts from conspecific females, but not to males, which indicates that some chemicals from females could be involved in sexual communication. A significant EAG response also was recorded in response to the extracts of fluids produced during 'reflex bleeding.' Male and female antennae of both species exhibited similar dose-response curves to most of the selected compounds, although female C. maculata antennae exhibited higher thresholds in response to several compounds including α- terpineol, (Z)-3-hexenol, and (4aS,7S,7aR)-nepetalactone. Field tests showed that 2-phenylethanol was highly attractive to both sexes of the two investigated species. Only C. maculata was attracted to traps baited with α- terpineol.