Effect of photoperiod on biological attributes of Harmonia dimidiata (Fab) (Coleoptera Coccinellidae) fed on Schizaphus graminum (Rond.) (Homoptera Aphididae) aphid

摘要

Ladybird beetle Harmonia dimidiata Fab. (Coleoptera: Coccinellidae) is voracious predator of aphid pests. The present study was conducted to check the effect of long photoperiod (16: 8) hours light: dark and short photoperiod (8: 16) hours light: dark on the biological parameters of H. dimidiata at 24 ±1 ?C with 60±5 % relative humidity fed on S. graminum aphid in growth chamber. The results showed that egg incubation period was 4.22±0.15 and 4.21±0.14 days under both long and short phtoperiod. The duration of first and second instar larvae was 2.43±0.09, 2.42±0.09 and 2.24±0.10, 2.28±0.11 days which was non significantly different from each other under both long and short photoperiods. The duration of third and fourth instar larvae were 4.41± 0.16, 3.65± 0.17 and 8.0±0.10, 7.21± 0.16 days respectively, which was significantly different from each other. The larvae duration was 17.08± 0.12 and 15.56± 0.34 days respectively, which was significantly different from each other. The results showed that the effect of photoperiod was not extended to all stages. The preoviposition period of adult female was 9.0±0.45 and 11.65±0.26 days respectively which was significantly different from each other while the oviposition and post oviposition period was non significantly different. The female fecundity was 668.7±32.46 and 612.6±36.08 eggs per female which was non significantly different from each other. The results showed that H. dimidiata completed their life cycle successfully and no reproductive diapauses were observed under both photoperiods. On the basis of the present results, H. dimidiata should be reared successfully under long photoperiod (16: 8) hours (light: dark), owing to shorter pre oviposition period and high fecundity rate of female lady bird beetles.