The biosystematics of British aquatic larval orthocladiinae (diptera: chironomidae)

Abstract

The relationships and subfamilial classification of the Chironomidae (Insecta: iptera, ematocera) are discussed and some comments made on the ecological significance of the range of larval habitats found in the family. The reasons are given for the selection of the aquatic larval Orthocladiinae for detailed morphological and ecological study. Following a review of previous taxonomic works and an analysis of the current views on the Orthocladiinae, a method for rearing aquatic larval Chironomidae is described. This method utilises disposable petri-dishes each containing a single larva, kept in a cooled incubator. This is followed by a list of fifty-two collecting sites throughout Britain with some physical and biological data for each site. Keys for the identification of the larvae of all known Holarotic genera are presented based on reared British material and incorporating published descriptions and examination of overseas specimens. Generic diagnoses to forty-one British genera of Orthocladiinae and descriptions and keys to ninety-one aquatic species are given. These have been prepared from examination of about 1,230 specimens, reared, collected and sent by correspondents. For each genus the relationships and phylogeny are discussed and for each species a full description is given using morphological terminology outlined in a previous chapter. Over four hundred illustrations in seventy-nine plates show the features of each species, many for the first time. Under each species all available ecological and distributional information is given. Eleven species either cannot be associated with adults or else appear to belong to undescribed species. In a concluding chapter the relationship between the phylogeny and ecology of the subfamily is discussed incorporating additionally information about genera with terrestrial and marine larvae. The importance of species identification especially for indicator organisms in pollution biology, as well as for calculations of diversity in freshwater habitats, is stressed.