Relationship between temperature and development of the ectoparasitoid Larra bicolor (Hymenoptera: Sphecidae) and the endoparasitoid Ormia depleta (Diptera: Tachinidae)

The rates of development of the second introduced strain (from Bolivia) of the ectoparasitoid wasp Larra bicolor and of the two introduced strains (from subtropical Brazil and from temperate Brazil) of the larviparous endoparasitoid tachinid Ormia depleta were determined when reared at both constant and field temperatures in northern Florida. The data were used to examine the performance of the accumulated degree-day model (DD) to predict field development of both natural enemies parasitizing the mole cricket Scapteriscus borellii. Development and survivorship were studied in incubation chambers at eight constant temperatures, 15.0, 17.5, 20.5, 22.5, 25.0, 27.5, 30.0 and 32.5 ± 0.1°C, at 14:10 (L:D) photoperiod. The relationship between temperature and developmental rate was estimated with linear regression analyses. Pooled developmental times for males and females were used to fit the linear regression models. The lower developmental threshold was estimated by the “x-intercept” method. Development of all stages of the wasp occurred at temperatures from 25.0 to 30.0°C. No development was observed at 17.5°C, and only one wasp developed at 22.5°C. Development of O. depleta occurred in the range from 17.0 to 30.0°C. The field development was determined by confining newly parasitized hosts into 15 x 5 cm (L x diameter) chambers, filled with autoclaved sand, buried underground at up to 60 cm depth that were operated during all parts of the year except the coldest months. Field experiments with L. bicolor were run during autumn. Temperature underground was recorded every 30 min during field experiments. A degree-day model based upon constant temperature was fitted to data from field experiments for each parasitoid species and strain. A full description is presented of the developmental time (and rates) in day units, for constant and field experiments, together with the regression coefficients from constant temperatures and the validation of both data sets using the accumulated degree-day model. Data about the wasp are summarized in life tables and its field efficacy in parasitizing mole crickets is presented and explained. Data about the fly comparing development per sex and per strain are presented also.