Uraba lugens (Lepidoptera: Noctuidae) and its parasitoids (Hymenoptera: Braconidae): temperature, host size, and development.
The relationships between temperature and development of Uraba lugens and between temperature, host size and development of its parasitoids, Cotesia urabae and Dolichogenidea eucalypti, were investigated. U. lugens underwent from 6 to 14 instars before pupation. The number of instars affected the allometry of head capsules. Females had more instars than males, and both sexes had more instars at lower temperatures. Thermal requirements for larval and pupal development of U. lugens differed between sexes; male larvae had lower temperature thresholds and male pupae higher temperature thresholds than females. Egg-larval rate of development of C. urabae after oviposition in small hosts was much slower than that after oviposition in mid-size hosts and differed between sexes. Pupal development of C. urabae was faster for males than females. Egg-larval development of D. eucalypti after oviposition in small hosts was more rapid than that of C. urabae from small hosts, whereas pupal development of D. eucalypti was slightly longer than that of C. urabae. When D. eucalypti were reared at 15°C, some individuals pupated when predicted by day-degree summation, and others delayed emergence from the host by a further 120-182 days, indicating a physiological delay in development. Simulation of the phenologies of U. lugens, C. urabae and D. eucalypti in the Adelaide region using thermal constants showed good fit between field-observed and predicted durations of life stages and confirmed the presence of a physiological delay in emergence of D. eucalypti in winter and during its second generation in summer.