The effect of larval density on growth and development of Tenebrio molitor

Abstract Day-old larvae of Tenebrio molitor were reared at 30 ± 1°C, 55 ± 5% r.h. and at densities of 1, 2, 5, 10 and 20 per 455 ml rearing jar. After 1 month, larvae reared at the density of 20 individuals were significantly larger than those at the density of 2 individuals, which were smallest. Greater average mass of larvae was correlated with increasing density after 1 month of development. However, female pupae and adults reared in isolation were significantly larger than those at densities of 10 and 20 individuals per jar. At these later developmental stages, greater mass of females was correlated with decreasing density. No significant difference was found between average mass of males at pupation or adult emergence with varying densities, nor was there any difference in time to pupation or time to adult emergence at any density for either sex. Female pupae were significantly larger than male pupae at densities of 1 and 2 individuals per jar; adult females were significantly larger than adult males only when reared in isolation. Percentage survival after 1 month was statistically similar at all densities, while at pupation and adult emergence isolated individuals had statistically greater percentage survival than those at high densities. Cannibalism and incomplete larval-pupal and pupal-adult transformations occurred more frequently at higher densities.