Abstract
The status given to Chironomus riparius and C. thummi by a number of authors since the original descriptions of these species by Meigen (1804) and Kieffer (1911), respectively, has been reviewed. Characters by which the two species have been distinguished were investigated and it was concluded that they are invalid. His descriptions suggest that Kieffer attributed the immature stages of a species in the taxon Glyptotendipes to the adults of C. riparius and this error appears to have been the source of considerable confusion. As nothing has indicated that C. thummi differs from C. riparius it was decided that the latter, being the older, is the correct name for the species. In the course of investigating this situation, tentative evidence has been discovered to suggest that both subspecies of C. riparius occur in Britain.