Pseudorthocladius immezensis sp. n., a new relict species inhabiting the Macun high-alpine stream, Swiss Alps (Diptera: Chironomidae)

Abstract

Male adult of Pseudorthocladius immezensis sp. n is diagnosed and described based on material collected in the high alpine cirque of the Macun area (Immez Lake basin, alt. 2616 m a.s.l.). A combination of morphological characters found in the male adult has allowed us to consider this new species as a local biogeographical representative of the eastern part of the Swiss Alps: coronal suture with lateral extension, low antennal ratio (AR 0.30); distal half of wing hairy; anal point broadly triangular with a characteristic enlarged base; inner apical margin of gonocoxite truncate; superior volsella large lobe-like; inferior volsella double, dorsal lobe nose-like and distinctly bent apically; virga present, with 4 spines; crista dorsalis absent. A differential diagnosis is given, in which some distinguishing morphological characters are summarised. Comments on the ecology and geographical distribution of the new species are also provided.