SOME EFFECTS OF TEMPERATURE ON THE IMMATURE STAGES OF THE ARMYWORM, PSEUDALETIA UNIPUNCTA (LEPIDOPTERA: NOCTUIDAE), UNDER CONTROLLED CONDITIONS

Abstract

Pseudaletia unipuncta (Haworth) was reared at eight constant temperatures from 5° to 31 °C. The eggs hatched at all temperatures except 5 °C. Development was completed at 13°, 17°, 21°, 25°, and 29 °C but at 10° and 31 °C none survived beyond the final larval instar.The duration of each stage decreased with rise in temperature up to 29 °C; but a further rise brought no further change, or even an increase. Developmental rates plotted against temperature gave shallow sigmoid curves with the maximum development rate near 29 °C for all stages except for the final instar larva where it was between 25° and 29 °C. Various alternating temperature regimes had no special influence on the rate of the development of eggs or larvae.There was a significant linear increase in larval head width with rise in temperature for all instars except the first. For larvae with six instars, the mean head width in the last instar ranged from 3.15 mm at 13 °C to 3.38 mm at 29 °C. At 13 °C some larvae required an additional moult to reach the apparent minimum size (about 3 mm) to complete development.