Diversity and Classification of Insects and Collembola

This chapter describes classification, anatomy, morphology, physiology, reproduction, life history, phylogeny, evolution, ecology, and taxonomy of orders and families in which one or more life stages are truly aquatic and adapted for survival under or on the water surface. It also briefly mentions another arthropod group, the semiaquatic springtails (class Entognatha, order Collembola). A total of 10 orders of insects contain aquatic species. Five of them (Ephemeroptera, Odonata, Plecoptera, Trichoptera, and Megaloptera) are aquatic orders in which almost all species have aquatic larvae. The remaining five orders (Heteroptera, Coleoptera, Diptera, Lepidoptera, and Neuroptera) are partially aquatic orders in which most species are terrestrial. However, these orders contain species or entire families that have one or more life stages adapted for living in an aquatic environment. Three aquatic orders (Ephemeroptera, Odonata, and Plecoptera) have a hemimetabolous life cycle, which includes three developmental stages: egg, larva, and adult. The other two aquatic orders (Trichoptera and Megaloptera) have a holometabolous life cycle, which includes four developmental stages: egg, larva, pupa, and adult. Four of the five partially aquatic orders (Coleoptera, Diptera, Lepidoptera, and Neuroptera) also have holometabolous life cycles. The fifth order, Heteroptera (Hemiptera), has a paurometabolous life cycle, which includes three developmental stages: egg, larva, and adult.