Effect of Larval Density on Pupation of Tribolium freemani HINTON (Coleoptera : Tenebrionidae)

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Abstract
The rate of pupation of T. freemani larvae was influenced by the population density but not by the conditioned diet and its diethyl ether or water extracts. Larvae at high densities (> 20/2 g wheat feed per vial) failed to pupate for > 6 mo., while those at lower densities (< 5/2 g wheat feed per vial) pupated within 1 mo. Isolation of the larvae that persisted in high density vials resulted in pupation within a short period of time. The prevention of pupation by increased larval density would be a main regulatory factor for controlling the population size, although cannibalism as in T. castaneum cannot be disregarded. The primary factor causing this density effect is discussed with respect to the endocrine secretion resulting from physical contacts with other larvae.