About a peculiar type of rheocrene spring in the High Atlas (Morocco). Description of a simuliid characteristic of this habitat, Simulium (Crenosimulium n. sg.) Knidirii n. sp. (Diptera, Simuliidae)

In the High Atlas we have studied a peculiar type of spring representing an environment close to the madicolous habitats. The main ecological characteristics of this habitat and of its community are given. Immature stages of a previously unknown simuliid fly are abundant. The species, Simulium knidirii n.sp., is described; it is closely related to Simulium lamachei Doby & David known from a few localities in southern France and in northern Morocco (Rif). The pupae of these two species differ from those of all palearctic Simuliidae mainly by their two-branched tube-like gills. Study of all stages has convinced us that both S. lamachei and S. knidirii represent a new subgenus, which we named Crenosimulium. The subgenus is limited in its distribution to a few isolated spring-fed streamlets in southern France and Morocco. The larvae, found almost exclusively attached to stones over which water trickles, are able to utilize the madicolous environments of such small streamlets. They feed by scraping benthic algae.