Host selection and sex allocation in Leptomastidea abnormis, a parasitoid of the citrus mealybug Planococcus citri

Leptomastidea abnormis (Girault) and Leptomastix dactylopii (Howard) [Hymenoptera: Encyrtidae] are the two parasitoid species frequently used for biological control of the citrus mealybug Planococcus citri (Risso) [Homoptera: Pseudococcidae]. As part of a programme to determine the best control practice, host size selection and sex allocation were studied in L. abnormis, and compared with those of L. dactylopii. L. abnormis showed a preference for the second size class, but also attacked third and fourth size class and adult mealybugs, while in previous studies L. dactylopii was found to prefer the third and fourth size class and adults, and never attacked second size class mealybugs. Female L. abnormis reared from parasitized mealybugs had a higher mean body mass than males, as is predicted by Charnov's theory on sex allocation. However, sex ratios of emerging L. abnormis did not differ between mealybug size classes. These results imply possibile coexistence of the two parasitoids. As field evidence suggests a more complex interaction between the two species, studying direct competition would be a useful next step.