Host location and acceptance in Psyttalia concolor (Szépligeti) (Hymenoptera Braconidae): role of host instar

Laboratory investigations on the role of host instar in host location and acceptance of naïve females of Psyttalia concolor (Szépligeti) (Hymenoptera Braconidae) were conducted. Ceratitis capitata (Wiedemann) (Diptera Tephritidae) larvae were used as hosts. A simple no-choice experimental test was performed, using oviposition dishes containing: (1) second instar host larvae or (2) late third instar (fully-grown) host larvae. The parasitoid:host ratio was 1:1. Results showed that significantly more P. concolor located hosts in dishes containing late third instar C. capitata larvae (100%) and fewer wasps located second instar larvae (16.7%). The relative failure of P. concolor to locate the latter larval stage in laboratory conditions it is likely to be related to the fewer vibrations produced by second instar hosts during feeding and/or movement. However, no host rejection behaviour was observed, with all located late third instar and second instar larvae being parasitized. Therefore, both instars will serve as suitable hosts for P. concolor