Smells good, feels good: oviposition of Chrysoperla carnea-complex lacewings can be concentrated locally in the field with a combination of appropriate olfactory and tactile stimuli

Abstract

Larvae of common green lacewings (Chrysoperla carnea species-complex) are important generalist predators, and can serve as valuable biological control agents. Since only larvae are predatory, oviposition is of crucial importance. Recently, a ternary floral bait was described, attractive to females that would then lay their eggs in the vicinity of the baits. Earlier studies have shown that females prefer to lay their eggs on spines and hairs of plants. In the present study, we tested whether the number of eggs laid could be increased by combining chemical, visual and tactile stimuli. Common green lacewings were caught equally well in baited funnel traps covered with white, yellow, fluorescent yellow, light blue or black sheets, showing no preference to any of the colours. In further tests the field effect of the ternary floral bait on the oviposition site choice of common green lacewings was confirmed, as in the absence of the bait only negligible numbers of eggs were recorded on egg-laying plates. In the presence of the ternary floral bait, lacewings laid more eggs on spiny than on smooth surfaces. Removal of previously laid eggs did not affect the number of eggs laid afterwards. Our studies demonstrated that by combining the ternary floral bait and an appropriate spiny surface, oviposition of common green lacewings can be increased and concentrated to a relatively small area. Possible practical applications are discussed.