Glacier brooks in Northern Scandinavia have been investigated for the occurrence of chironomid larvae and pupae. In the uppermost zone of glacier brooks with a very narrow temperature amplitude, Diamesa lindrothi is the most abundant species. In a lower zone with a wide diurnal temperature amplitude during summer months, the simuliid Prosimulium macropyga is more abundant, along with other species of Diamesa. Lacking any primary organic production, the diptera larvae living here feed on particles drifted up on the glacier surface, conserved there and released into the glacier brook by the melting of the ice. The larvae of Diamesa lindrothi have developed adjustments to obviate the strong water current and the instability of the benthic substratum: The mature larvae spin nets over small stone cavities where they live, and thus prevent the pupal stage from being washed downstream. The Diamesa associations in glacier brooks have to be regarded as distinct freshwater biocoenoses. They have to be considered as belonging to the biocoenosis type kryon, and the brooks themselves according to the biotope type kryal. They differ from the krenal and rhithral biotope types by both abiotic and biotic peculiarities, and from the equivalent biocoenosis types by their characteristic life forms and animal associations.