Effect of temperature, food density and sub-lethal exposure to malathion on aging in Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae)

Abstract

The lifespan of an inbred strain (SS) and an outbred strain (GV) of Cryptolestes ferrugineus (Stephens) was determined at several different environmental conditions, and the reproductive capability of adults of the SS strain kept as isolated virgins until the age of 30 weeks or greater was determined. The developmental period of immature stages reared individually in separate gelatin capsules containing ground wheat plus wheat germ was inversely correlated with temperature and ranged from 22 days at 35°C to 71 days at 22°C. At constant temperatures of 25, 30 and 35°C the lifespan of both strains was inversely correlated with temperature. Mean adult lifespan ranged from 22 weeks at 35°C to 41 weeks at 22°C for the SS strain, and from 24 weeks at 35°C to 50 weeks at 22°C for the GV strain. On a temperature schedule starting at 30°C, decreasing in steps to 5°C, then increasing in steps to 25°C, the mean adult lifespan of each strain was more than 40% longer than it was on a temperature schedule starting at 22°C, decreasing to 5°C, then increasing to 25°C, although the overall weighted means of both temperature treatments were similar. Beetles of both strains lived longer on ground wheat plus wheat germ than on whole kernels of wheat that had the seed coats over the germs removed. Exposure to malathion-treated wheat that killed 24% of the population did not shorten the lifespans of survivors. Significant numbers of old adults were able to reproduce: 8 of 10 30-week-old male/female pairs aged at 30°C produced offspring; 2 of 10 one-year-old male/female pairs aged on the temperature schedule starting at 30°C, decreasing to 5°C, then increasing to 25°C, produced offspring.