A revision of the British leeches of the family Erpobdellidae, with a description of Dina lineata (O. F. Müller, 1774), a leech new to British fauna

Abstract

Summary. Revised descriptions of the British leeches of the family Erpobdellidae are given, together with accounts of their principal variations. Since the British Erpobdellidae cannot with certainty be identified by examination of external characters, a technique is described for separating the genera and species by the shape of the genital atrium. The leech Dina lineata (O. F. Müller, 1774) is recorded in Britain for the first time. It was collected in a roadside pond rich in calcium and in organic matter. It is an isolated occurrence, probably an example of recent colonization. Erpobdella testacea cannot establish itself in an environment favourable to E. octoculata, but in conditions of sewage pollution, or low total alkalinity, E. testacea becomes dominant. The division of E. octoculata into var. vulgaris and var. atomaria is of no taxonomic significance, and should be discontinued. Trocheta subviridis has been found most frequently in London and the Home Counties, but also occurs in Manchester, Gloucester, Glamorgan and Oxford. It is frequently associated with sewage works.