Longevity and body weight loss of silkworm moth, Bombyx mori, varied by different temperature treatments

Abstract

The adult of silkworm, Bombyx mori, has a very short lifetime, since it lives without taking food after emergence. The body weight at emergence took on a seasonal variety, when reared at optimal temperature (25°C); about 1·4 times heavier in spring than in autumn. These were, however, few seasonal differences of the mean and maximum life spans. All metabolisms and the rate of living of silkworm moth appear to be accelerated by such high temperatures as 30 and 35°C, resulting in shortening their life span by 50%. On the contrary, the moths kept at 4°C maintained life approximately five times longer than the moth at optimal temperature. The final body weight level of the moth exposed to cold never fell to the final weight level at the optimal temperature. It might be difficult to account for the elongation of the life span only by a moderate disturbance of metabolic processes at the low temperature. Neither correlations between life span and body weight at emergence nor between life span and body weight at death were recognized by the every temperature treatment. Energy corresponding to about a quarter of body weight at emergence was utilized for basic metabolisms necessary to maintain the minimal life, muscle movements and oviposition at the optimal temperature. Oviposition of virgin females was promoted by high temperature treatments, but inhibited by low temperature. The ratio of total oviposition days to mean life span was almost comparable between optimal and high temperature conditions. Only at low temperature the ratio was less than that at optimum. During the adult period three increasing phases of death number were observed. Oviposition in females did not seem to be concerned with the second increase phase in the middle ages.