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Host-handling behavior is an important aspect of parasitoid foraging behavior. When a parasitoid encounters a potential host, the handling behavior starts with the evaluation of the host and continues if the host has been judged acceptable. Host handling is usually terminated after egg laying or host feeding and host marking. Host-handling behavior of an arrhenotokous population of two Eretmocerus species, E. mundus Mercet and E. eremicus Rose and Zolnerowich, along with a thelytokous population of E. mundus were compared under laboratory conditions. Several elements of host-handling behavior, including encountering, ascending, turning on host, descending, preening, egg laying, and host feeding were recorded. There were no correlations among the durations of these phases across parasitoid populations/species or host nymphal instars. Duration of different phases of host-handling behavior showed only slight and sometimes significant differences between different Eretmoceruspopulations/species. The actual laying of the egg had the longest duration of all host-handling behaviors, and was longer on third nymphal instars than on younger ones. Females of the three populations/species accepted the first three nymphal stages either for egg laying or for host feeding. Females spent a lot of time to make wounds in the host when preparing for host feeding, and eventually killed the host. The implications of these findings for the use of the different Eretmoceruspopulations/species in biological control are discussed.

Eretmocerus species (Hym. Aphelinidae) are solitary parasitoids of Bemisia tabaci (Gennadius). Mate finding and mating behavior of two species, E. mundus and E. eremicus, were studied under laboratory conditions. We used three populations of Eretmocerus: typical arrhenotokous populations of E. eremicus ( from USA) and E. mundus ( from Spain), and an atypical thelytokous population of E. mundus ( from Australia). We studied the intra- and interspecific responses of males to volatile and nonvolatile components of the female sex pheromones, mating behavior, and hybridization between populations and species. In both arrhenotokous populations, males reacted to volatile pheromones by walking toward conspecific virgin females. Males also reacted to nonvolatile pheromones by spending more time on and around patches on leaves of poinsettia plants that had been exposed to virgin females. Males of E. eremicus showed the same reaction to the nonvolatile sex pheromone of E. mundus females, but E. mundus males did not show any reaction to the nonvolatile sex pheromone of E. eremicus. There was no response of males of both species to thelytokous females of E. mundus. In both species three phases were distinguished in the mating behavior: premating, mating, and postmating. The duration of the phases differed between the three populations. Successful copulation between the two Eretmocerus species did not occur. In contrast, we recorded some successful copulations between Australian males and Spanish females of E. mundus, but they did not produce any hybrid females.