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Abstract:
The discovery of an extant population of Perla imhoffi Pictet, a species once common in the upper Rhine and other rivers on the north slopes of the Alps, led to a reconsideration of the genus Besdolus Ricker, of which it is the type species. Besdolus is reinstated as valid genus of Perlodidae on the basis of distinctive generic characters. It is removed from synonymy with Dictyogenus Klapalek, a genus thought to represent its sister group. Four species are assigned to the previously monotypic genus Besdolus: B. imhoffi (Pictet), B. ventralis (Pictet) comb. n., B. bicolor (Navas) comb. n., and B. ravizzarum sp. n. The incompletely known larva and egg of B. imhoffi are fully described, and notes on habitat and egg biology are presented. The proper identity of B. ventralis (Balkan Peninsula and a narrow stretch along the northern edge of the Alps) is established, and its male and larva are described for the first time. Presumed Italian B. ventralis are described as B. ravizzarum sp. n. (northern Italy, southern France). B. bicolor from Spain is removed from synonymy with B. ventralis and redescribed. Keys to species are provided for males, last instar larvae, and eggs.
