DIFFERENCES IN LIFE-HISTORY TRAITS BETWEEN ISOFEMALE LINES OF THE APHID PARASITOID APHELINUS-ABDOMINALIS (HYMENOPTERA, APHELINIDAE)

Six isofemale lines of the aphid parasitoid Aphelinus abdominalis (Dalman) were compared for life history traits related to parasitism of three cereal aphid species. The lines differed most in the number of hosts parasitized in 24 h and the developmental times of females and males. Cluster and discriminant analysis showed that these differences were pronounced between line I, line II and lines III-VI, but not between lines III, IV, V and VI. Cross-breeding experiments revealed reproductive barriers between the lines which proved to differ most in life history traits, indicating the possible existence of morphologically similar species. Given the variability in life history traits between lines of A. abdominalis recorded in this study, we suggest a careful selection of candidate strains for biological control will be rewarding.