Temperature Regulation of Larval Size and Development in Attagenus megatoma (Coleoptera: Dermestidae)1

Abstract

Growth responses of the black carpet beetle, Attagenus megatoma (F.), reared individually on Purina diet at 20, 25, 28, 30, and 35°C are compared. Although size of male and female larvae and pupae is correlated to rearing temperature between 20 and 30°C, time to pupation is independent of temperature in this same temperature range. Larvae reared at 35°C have the highest initial growth rates and obtain the heaviest weights. However, pupation rates are lowest at 35°C and almost half fail to pupate after 475 days (mean time to pupation at 28°C is ca. 270 days). Two larval growth phases are observed at temperatures from 20 to 30°C. There is a predominant initial phase in which about 75% of final larval weight is obtained and a second phase of growth that begins at about 170 days and continues to pupation. The only appreciable weight gain for larvae reared at 20°C occurs during the second growth phase. Low temperature treatments with different age A. megatoma larvae indicate that the younger the larvae are when given an 8-week cooling period at 15°C, the shorter the time to pupation after return to 28°C. Thus, for larvae between 6 and 20 weeks of age a linear relationship exists between larval age and sensitivity to cooling. In addition, pupation rates are correlated to rearing temperature subsequent to cooling. In this case, pupation rates are fastest after return to 35°C. However, when larvae are transferred directly from 28 to 35°C without prior cooling, pupation is strongly inhibited. Effects of both constant and fluctuating temperatures during development are discussed in relation to the larval diapauselike condition that occurs in this dermestid species.