The difference in the developmental period and mortality of some field strains of Oryzaephilus surinamensis (L.) at constant temperatures (Coleoptera: Silvanidae)

The development and mortality of eight field strains of Oryzaephilus surinamensis (L.) was studied on kibbled wheat at 70% r.h. and 18.5, 20 and 25°C with a light regime of 12L:12D. Eggs of all strains hatched in approximately 6 days at 25°C. The mean egg period rnaged from 10.9 to 13.9 days at 20°C and 14.2 to 16.2 days at 18.5°C. Egg viability was generally high for all strains except at 18.5°C, where only 34.6 and 42.5% of eggs hatched for two of the strains. At 25°C, the mean larval period ranged from 16.0 to 21.5 days, from 35.1 to 51.9 days at 20°C and 53.9 to 76.0 days at 18.5°C. Larval mortality was low for all strains at 25°C but was much more variable amongst strains at lower temperatures. There appeared to be little difference in the duration of the pupal period for each strain at a given temperature. However, pupae of four of the strains all died at 18.5°C as did those of two strains at 20°C. Where pupae developed at these temperatures, mortality was high for all strains. Fewer deaths were recorded for each strain at 25°C. The results are discussed in relation to development and survival under temperate climatic conditions.