POPULATION-GROWTH POTENTIAL OF EPIPHYAS-POSTVITTANA, THE LIGHTBROWN APPLE MOTH (LEPIDOPTERA, TORTRICIDAE) IN RELATION TO DIET, TEMPERATURE AND CLIMATE

Life-history parameters and developmental rates of Epiphyas postvittan a were determined for four natural food plants and Shorey's diet at ea ch of six temperatures. The rate of development of larvae and the life -history parameters were influenced by both temperature and diet. The highest r(m) value was given by populations feeding on Plantago lanceo lata, followed by those on Shorey's diet and Rumex crispus, all at 25 . 2 degrees C, then by Malus pumila at 19 . 9 degrees C and Trifolium repense at 25 . 2 degrees C. Zero population growth occurred at 7 . 1 and 30 . 7 degrees C. A life-table study of five geographical strains of the moth under non-variable conditions (constant temperature and ar tificial diet) showed that finite rate of increase (lambda) was signif icantly correlated with climatic features of habitats, viz. mean annua l Values of temperature, rainfall and relative humidity. Peak values o f lambda occurred at cooler temperatures, moderate levels of habitat m oisture and high altitudes (500-1000 m); the Canberra population gave the highest value (lambda = 1 . 157), followed by Armidale (lambda = 1 . 152), Melbourne (lambda = 1 . 141), Mildura (lambda = 1 . 135) and Auckland (lambda = 1 . 118). Higher performance of E. postvittana on h erbaceous plants than on woody plants suggests that it primarily evolv ed as a feeder on herbaceous plants.