Developmental characteristics of Tenebrio molitor larvae (Coleoptera: Tenebrionidae) in different instars

Abstract

Tenebrio molitor is a major pest of stored grain, although its larvae have potential for useas food. However, little is known about the characteristics of individual larval instars of thisspecies, and the number of instars remains disputed. Therefore, we assessed T. molitor forthe average number of instars and its characteristics at different larval stages. The focusof this study was to establish a foundation for further studies on the characteristics of eachlarval instar. All of the T. molitor larvae showed incubation periods of 7 to 8 d and a periodof 3 to 4 d for the 1st instar. Beyond the 1st instar, there were relatively large variations in thenumber of days in each instar period. Before emergence, most of the larvae had typicallygone through 15 to 17 instars. The highest rate of pupae formation, 28.32%, was observed inthe 17th instars. The body length gradually increased with each successive instar, reaching itsmaximum at the 17th instar. Beyond the 17th instar, however, the body length decreased. Thelarvae were white in the first instar, and gradually turned brown after the 2nd instar.