Effect of moisture on growth rate and development of two strains of Tenebrio molitor L. (Coleoptera, Tenebrionidae)

Abstract

Larvae of Tenebrio molitor L., reared on dry wheat shorts, grew and developed much more rapidly when free-choice water was available than when it was not. When water was supplied in cotton pads, larvae often burrowed in the moist pads and could obtain water by cuticular absorption or ingestion. Heavier larvae were also produced at pupation with a tendency for reduction of larval and pupal mortality and an increase in adult longevity in the water regimen. Two strains of T. molitor showed highly significant differences in their rates of growth and development. The faster developing strain in the dry condition also developed faster when free-choice water was available and weighed more as prepupal larvae, pupae and adults. Water also reduced the number of molts in the faster-developing strain. Although the mechanisms enabling more rapid growth under both dry and moist conditions are not known, strain differences in mealworms indicate genetic potential for completing life cycles more rapidly in dry environments with extremely rapid development possible under optimum moisture conditions.