TEMPERATURE-DEPENDENT DEVELOPMENT OF THE SPECKLED GREEN FRUITWORM, ORTHOSIA-HIBISCI GUENEE (LEPIDOPTERA, NOCTUIDAE)

Temperature-dependent development of eggs, larvae, and pupae of the sp eckled green fruitworm, Orthosia hibisci Guenee, at constant temperatu res of 5-30.0 degrees C, 7.5-27.5 degrees C, and 0.8-20.8 degrees C, r espectively, was described. Development times decreased with increasin g temperatures and minimum developmental times in eggs, larvae, and pu pae occurred at ca. 27.5, 25, and 20.8 degrees C, respectively. Variat ion in development times of all life stages was modelled accurately (R (2) values 0.98-0.99) with a Weibull distribution. Relationships betwe en temperature and developmental rates of all life stages were describ ed by linear degree-day (DD) and nonlinear poikilotherm models. There were significant differences (ANOVA, P < 0.05) among the slopes of reg ression equations describing developmental rates of different life sta ges and larval instars. Minimum developmental temperatures far eggs (3 .4 degrees C), first- through fifth-instar larvae (4.7, 2.9, 3.6, 3.5, and 3.7 degrees C), and pupae (2.8 degrees C) were determined by extr apolation of linear regression equations to the x-intercept. Median de velopment time of eggs, first- through fifth-instar larvae, and pupae required 99.0, 44.2, 51.5, 52.4, 57.1, 69.9, and 61.3 DD above the min imum developmental temperatures, respectively. Developmental rates of eggs and all larval instars averaged were described by six-parameter m odels exhibiting low- and high-temperature inhibition. Development of pupae was best described by a four-parameter model exhibiting low- but no high-temperature inhibition. This information should be useful for developing a phenology model to improve management actions against O. hibisci.