Larval Chaetotaxy of World Dytiscidae (Coleoptera: Adephaga) and Implications for the Study of Hydradephaga

Abstract

Although the Dytiscidae (Coleoptera) are among the most common insect inhabitants of freshwaters, knowledge of their larval morphology is scanty throughout the World. The identification of larvae is a continuing problem because the literature available to accomplish this is scattered, limited to certain groups, outdated, difficult to use or non-existent. Recent studies have demonstrated the taxonomic and phylogenetic value of chaetotaxy in studying larval Dytiscidae. The study of body sensilla (setae and pores) was shown to be useful and important both for diagnosis and study of phylogenetic relationships among taxa. The fact that all these studies were conducted separately over a period of more or less 30 years, however, does not facilitate comparison among taxa. This chapter synthesizes these studies into a more comprehensive approach, which should facilitate comparison among the dytiscid subfamilies. Although this framework is useful for the study of larval morphology of the Dytiscidae, it has also recently contributed to the study of larvae of other families of Hydradephaga, namely Aspidytidae, Gyrinidae, Haliplidae, Hygrobiidae, Meruidae and Noteridae. A corollary objective of this chapter therefore is to illustrate the power of larval chaetotaxy for testing hypotheses of phylogenetic relationships of Hydradephaga.