Effects of prior experience on host selection and host utilization by two populations of Anisopteromalus calandrae (Hymenoptera: Pteromalidae)

The effect of adult learning through an oviposition and host feeding experience was studied in two populations of Anisopteromalus calandrae (Hymenoptera: Pteromalidae), in choice and no-choice experiments in the laboratory using last instars of rice weevil, Sitophilus oryzae L., and lesser grain borer, Rhyzopertha dominica (F.), as hosts. In choice experiments, 20 wheat kernels infested by rice weevil and 20 by lesser grain borer were placed randomly in petri dish (15 by 100 mm) arenas. In no-choice experiments, 10 host-infested wheat kernels, either with rice weevils or with lesser grain borers, were mixed thoroughly in 500 g of uninfested wheat placed in a 0.945-liter glass jar (75 by 170 mm) arenas. A. calandrae females from a laboratory and field populations that were experienced with host larvae or naive were introduced singly into each experimental arena and allowed to sting and oviposit for 24 h. An oviposition experience with rice weevil or lesser grain borer had a stronger effect on host preference in choice experiments compared with experiments with naive wasps. Host-finding and parasitism rates were increased by prior experience with rice weevils in no-choice experiments. A. calandrae females clearly preferred rice weevil larvae for parasitization over larvae of lesser grain borer regardless of parasitoid population or prior experience. Also, A. calandrae females chose rice weevil larvae for producing female progeny and lesser grain borer for male progeny in choice experiments. The implications of the results of this study are discussed in relation to host preference and the selection of parasitoid populations for biological control programs in stored grains.