Effect of temperature and photoperiod on development and fecundity of an acarophagous ladybird beetle,Stethorus gilvifrons

Abstract

The development, fecundity and survival ofStethorus gilvifrons Mulsant (Coleoptera: Coccinellidae) fed onTetranychus cinnabarinus Boisduval (Acari: Tetranychidae) were recorded at three constant temperatures (20, 25 and 30±1°C) and 50±10% relative humidity, under two photoperiods (16:8 L:D and 8:16 L:D) produced using artificial light (4000 lux). The development rate for the egg stage (r[Te]) increased linearly with increasing temperature (r[Te]=0.0132*T − 0.0955; R2=0.95). The theoretical egg-development threshold was estimated to be 7.24°C; 75.75 degree-days (DD) were required for hatching. The total development time (r[Tt]) also decreased linearly with increasing temperature (r[Tt]=0.0039*T − 0.0325; R2=0.98). The development threshold was estimated to be 8.33°C and full development from egg to adult required 256.41 DD. Higher temperatures resulted in a shorter generation time (T 0) and decreased net reproductive rate (R 0). The length of the previposition and postoviposition period, as well as longevity, decreased significantly with increasing temperature under both photoperiods. The oviposition and postoviposition periods, longevity, and total fecundity were not significantly affected by photoperiod. The values of both the intrinsic rate of increase (r m ) andR 0 were highest under the long-day photoperiod at 25°C. The mortality rate was lowest at 20°C under the short-day photoperiod. Of the conditions tested, the optimum temperature for rearingS. gilvifrons was 25°C and the optimum photoperiod was 16:8 L:D.