Comparative morphology of the larval mouthparts among three Actias (Lepidoptera: Saturniidae), with descriptions on atypical spinnerets

Caterpillars are important for humans by some species causing great losses in Agriculture, and some others producing silk as fibers for our textile industry. Both food intaking and silk producing behaviors are undertaken by components of larval mouthparts. Mouthparts are morphologically specialized into various forms to exploit extraordinarily range of food resources. However, the morphological differences between congeneric larvae were rarely mentioned before. In this study, the larval mouthparts of Actias selene, A. sinensis and A. dubernardi were morphologically compared using scanning electron microscopy. The larval mouthparts exhibit significant differences on the morphology of labral notch, mandibles and spinneret among the three species. Firstly, the labral notchs are shallow in larvae of A. selene and A. sinensis, but significantly deeper in the larvae of A. dubernardi. Secondly, the teeth of mandibles are only arranged on the distal margin in A. selene and A. sinensis, but two rows in A. dubernardi. Furthermore, the atypical larval spinnerets are morphologically diverse, with the lateral lobes various in shapes among the three species. The morphological differences are very likely related to the divergence of feeding habits on their special host plants. The larval spinnerets are peculiar for bearing flake lobes laterally, which are rarely mentioned in previous studies.