the effect of different nymphal stages of aphis fabae scopoli on some biological features of thelytokous population of lysiphlebus fabarum (marshall)

understanding of parameters that influence parasitoids fitness is necessary for mass rearing and effective use of parasitoids. host quality is an intrinsic feature that is determined by quantitative and qualitative differences in hosts. these differences can change nutritional resources available and consequently affect life history traits of parasitoid. in this study, parasitoid wasps lysiphlebus fabarum were reared on different growths stages of black bean aphid, aphis fabae scopoli, including four instars and adult aphid, to identify the parameters determining fitness of wasp. the results showed that total development time was increased with host body size, such that these periods were determined 10.75±0.08, 11.57±0.07, 11.93±0.13, 12.59±0.10 and 12.61±0.06 days from 1st to adult aphids, respectively. body sizes of wasps were reared in 1st, 2nd, 3rd, 4th instar nymphs and adult aphids did not follow any specific function. the largest wasps were produced in second nymphal instar of aphids and then adult aphid, third, fourth and first nymphal instars were respectively. the highest emergence rate was obtained in wasps reared in adult aphid with 95.91% and the lowest emergence rate was 81.57% in fourth nymphal instar. furthermore, rearing the wasps in different growth stages of the aphid had a significant effect on the wasp longevity, and maximum longevity was observed in the wasps reared in third nymphal instar. according to this study, the greatest fitness was achieved when the wasps were reared in second nymphal instar of aphids.