Ovipositional behavior of the alfalfa seed chalcid (Hymenoptera: Eurytomidae) in response to volatile components of alfalfa

Behavior of the alfalfa seed chalcid, (Gussakovsky), during site selection and oviposition is described. Seed development and morphological changes in seed are also described for the period that seeds are susceptible to oviposition by chalcids. Females laid significantly more eggs when exposed to myrcene, hexyl acetate, (Z)-3-hexenyl acetate, caryophyllene, octa-3-one, and beta -farnesene. Since octan-3-ol. gamma -muurolene, 2-phenylethanol, and beta -farnesene are concentrated in seed pods, the lower rate of emanation of these compounds from undamaged pods may also provide chemical stimuli that help females distinguish seed pods from other parts of the plant. Volatile components in alfalfa that had an effect on oviposition varied substantially in concentration among plant parts; none occurred only in pods.