Separation of two species standing asHelophorus aquaticus(L.) (Coleoptera, Hydrophilidae) by banded chromosome analysis

摘要

Abstract.Methods are described for making chromosome preparations from developing embryos ofHelophorus, for producing C‐ and G‐banding, and for staining the nucleolus organizer with silver. These methods are used to compare the karyotypes of two species currently included inH.aquaticus(L.). It is shown that these species differ because of reciprocal translocations between some chromosomes, and that they would therefore be unable to produce fertile hybrids. Morphological differences in the male and female genitalia are described, and the range of aedeagal variation shown by each species is established by reference to chromosome preparations from testis. Reference to the relevant type specimens shows that the two species areH.aequalisThomson andH.aquaticus(L.). The latter is not a British species. Differences in the egg cocoons and third instar larvae are described. The present distributions and Pleistocene histories of the two species are descri