Paradoxical larval molts – autapomorphy of the order Lepidoptera

For all examined species of butterflies and moths (Lepidoptera), common peculiarities of larval molts are revealed, which distinguish them from all other insects: with the molt from one larval instar to another, living tissues of head and thoracic legs undergo significant destruction; the remaining tissues of the head shift backward and are partly impressed into the prothorax, and the remained tissues of the legs are shortened; with the ecdysis, the old head capsule is not broken by the Y-shaped suture, but is shed as a whole. In contrast to the larval molts, the molt from larva to pupa in most lepidopterans (except Gracillarioidea) passes without shifting of the head and legs tissues, and the cuticle of head capsule breaks by the Y-shaped suture. Peculiar adaptations allow lepidopteran larvae to live through long-term immobility of the head and the legs during each molt which separates two active larval instars. The set of species examined by us allows to express a statement that the peculiar mode of larval molt is inherent to all lepidopterans and differentiates them from all other insects, i. e. is an autapomorphy of the order Lepidoptera.