Orientation of Hippodamia convergens (Coleoptera: Coccinellidae) larvae to volatile chemicals associated with Myzus nicotianae (Homoptera: Aphidiidae)

Abstract

Larval coccinellids are thought to exhibit random search behavior but recent work has suggested that closer analysis of search paths could reveal more olfaction-driven behavior than previously realized. To test this idea, the use of volatile chemical cues by larvae of the coccinellid Hippodamia convergens Guérin-Méneville in searching for prey tobacco aphids, Myzus nicotianae Blackman, were studied. Larvae (second, third, and fourth instars) were exposed to three volatile sources; aphids alone, aphids on tobacco leaves and tobacco leaves previously exposed to aphids. Larvae were placed in an arena and their search path traced onto a grid then divided into seven different components relating approach angles and velocities at various time intervals. In general, older larvae were more efficient at searching than were younger ones, Older larvae had lower approach angles and higher approach velocities associated with treatments than did younger larvae. Different search behavior components responded differently to the various treatments but in most cases significant effects attributable to olfactory cues were obtained. The results support the potential use of olfactory cues by these larvae and suggest that a more extensive set of analyses and treatments should be conducted.