The precocious commitment of wing anlagen in Tenebrio molitor revealed by the addition of 20-hydroxyecdysone

An injection of 20-hydroxyecdysone (10 μg per animal) 6–13 days after the moult of the last larval instar of Tenebrio molitor induces the development of prothetelic larvae and larval-pupal intermediates. The state of larval-pupal switchover, or commitment, is only disclosed at the time of injection of the moulting hormone. Prothetelic A and B larvae, with small and medium sized wing Anlagen, undergo another larval or pupal instar. Prothetelic C larvae with bigger Anlagen are unable to moult, but the adult programme is expressed. Ecdysed larval-pupal intermediates give more or less perfect adults, while unecdysed mealworms, imprisoned in their larval cuticle, also expressed the adult programme. The commitment of Tenebrio is not a global switchover because a significant asynchronisation is noted between the development of organs considered. Animal crowding induces a delay in the appearance of wing Anlagen.