THERMAL RESPONSES IN THE CITRUS-FRUIT-FLY, DACUS-TSUNEONIS - EVIDENCEFOR A PUPAL DIAPAUSE

Thermal responses controlling pupariation and adult eclosion in a citr us fruit fly, Dacus tsuneonis (Miyake), were studied to understand the winter biology of this species. When mature larvae were exposed to va rious temperature conditions, the highest percentage of pupariation wa s obtained at 15 degrees C, although the variance at this temperature was greater than at 20 degrees C or 25 degrees C. Pupariation occurred most rapidly at 20 degrees C and an alternating temperature with a me an of 15 degrees C. At constant 15 degrees C, pupae failed to emerge a s adults. Pupae were characterized by a reduced respiration rate, whic h is typical of a diapausing pupa. When insects were stored at differe nt temperatures for 45 days after pupariation, and then transferred to 25 degrees C, adult eclosion occurred earlier when the initial temper ature was 10 degrees C than when it was 5 degrees C or 15 degrees C. A dult eclosion occurred most synchronously and pupal mortality was lowe st when insects were stored at 15 degrees C for 90 days before incubat ion at 25 degrees C. These results strongly suggest that D. tsuneonis enters a pupal diapause.