COMPARISON OF DEVELOPMENTAL RESPONSES TO TEMPERATURE IN APHELINUS-ASYCHIS (WALKER) FROM 2 DIFFERENT GEOGRAPHIC REGIONS

Aphelinus asychis (Walker) was imported to the United States for class ical biological control of the Russian wheat aphid, Diuraphis noxia (M ordvilko). Temperature effects on development of A. asychis colonies f rom two geographic regions (hereafter referred to as strains) were mea sured at four different temperatures (14, 18, 22, and 26 degrees C) us ing the Russian wheat aphid as the host species. Developmental thresho lds for development from egg to the adult stage were 8.2 and 9.3 degre es C, respectively, for strains collected near Pingluo, China, and Set te, Morocco. Corresponding degree-day requirements were 229 and 198 fo r the two strains. The Chinese strain required less time than the Moro ccan strain to develop from egg to mummy, while the Moroccan strain re quired less time to develop from mummy to adult. Differences in charac teristics of stage-specific development in relation to temperature are discussed in relation to the climate of the place of origin of the st rains.