Fall Armyworm Symposium: Effects of Constant and Fluctuating Temperatures and Humidities on the Survival of Spodoptera Frugiperda Pupae (Lepidoptera: Noctuidae)

Abstract

Pupae of the fall armyworm, Spodoptera frugiperda (J. E. Smith), were maintained in the laboratory for emergence under selected constant and fluctuating temperatures and humidities. Temperatures ranged from 10 to 40@*C, with a vapor pressure deficiency maintained constant at 8.5 mb in one study. No eclosion occurred at 10@*C or at 40@*C. Insects held at 15 and 35@*C had low survival and a high percentage (39-62%) were deformed. The optimum rate of development occurred at 30 and 35@*C, but a high percentage (58% of males, 39% of females) of the insects held at 35@*C emerged deformed. In a comparison between the constant and fluctuating temperatures (the mean of the fluctuating temperature equalled the constant temperature treatment), survival was not affected, but development was generally faster with the fluctuating treatment. In another study, relative humidity ranged from 20 to about 100% (33.9 to about 0 mb) and was maintained at 30@*C. Percentage survival, rate of development, or percent deformity were not affected by humidity. Weight loss was similar among insects held under different humidity treatments and was not affected by constant or fluctuating condition. Although survival was the same for the sexes, females developed at a faster rate and a smaller percentage emerged deformed as compared with males.