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 lacewi ng, Chrysoperla carnea in response to semiochemicals emitted from one of th eir prey species, the pea aphid Acyrthosiphon pisum and their host plant. E AG responses were also recorded from C. maculata in response to extracts fr om individuals of the opposite sex and to extracts from an herbaceous plant , catnip Nepeta cataria. Extracts of catnip and two sex pheromone component s of aphids, (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol, e licited significant EAG responses from the antennae of both predatory speci es. Of 10 corn Volatile compounds tested, C. carnea adults responded most s trongly to 2-phenylethanol and (E)-beta-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 e licited by most of the tested corn Volatile compounds, except alpha-pinene and (E)-2-hexenal. The highest EAG responses were observed in response to ( E)-beta-farnesene, alpha-terpineol, 2-phenylethanol, and beta-caryophyllene . Sexual differences in EAG responses of C. maculata were only found in res ponse to 1-octen-3-ol. Male antennae of C. maculata produced significant EA G responses to extracts from conspecific females, but not to males, which i ndicates that some chemicals from females could be involved in sexual commu nication. A significant EAG response also was recorded in response to the e xtracts of fluids produced during "reflex bleeding." Male and female antenn ae of both species exhibited similar dose-response curves to most of the se lected compounds, although female C. maculata antennae exhibited higher thr esholds in response to several compounds including alpha-terpineol, (Z)-3-h exenol, and (4aS,7S,7aR)-nepetalactone. Field tests showed that 2-phenyleth anol was highly attractive to both sexes of the two investigated species. O nly C. maculata was attracted to traps baited with alpha-terpineol.