Systematics of aquatic beetles (Coleoptera): current state and future directions

With more than 13 000 described species (Fig. 1, Table 1), water beetles are one of the most globally abundant groups of aquatic insects. Among insect orders, only Diptera has more aquatic taxa (though just as larvae) than Coleoptera, and the two largest water beetle families, Dytiscidae and Hydrophilidae, each have more species than either Ephemeroptera or Plecoptera. This rich diversity is not the result of a single aquatic invasion, but...