| Summary: | Summary Insects frorn running waters are of special interest for the study of the intrinsic biogeographical and ecological situation of the Continent of South-America. Dealing with the aquatic Insects of this region, we distinguish two groups, i.e. the cool-adapted group of the mountainous streams and torrents (rhithron) and the warm-adapted group of the water bodies of the tropical plains (potamon). Cool-adapted, oligostenothermic groups reveal a rather rich set of biotypes (`Lebensformtypen' in the meaning of REMANE) and are to be found in three mountainous areas, in which they occur in endemic genera which are equivalent representatives of the respective biotypes. The continent, thus, is divided into three biogeographical regions (see fig. 2). Concerning the geographical provenance, we distinguish two types: paleo-antarctic elements, i.e. old inhabitants of a formerly connected region (embracing South-America, Australia-New Zealand and Antarctica), and nearctic elements, which in late Tertiary or even later invaded the neotropical biocenoses from the North (see fig. 5). The degree of differentiation on the species-level is regular and matches the poor chances of isolation which the geomorphological structures of South-America offered during the glaciations. (Comparing the degree of differenciation on species-level between the two continents of Europe and South-America, a rather hypernormal rate of saturation within European biocenoses is evident, as seen in fig. 7). The extension of the respective ecological niches is large; in flight-period as well as in choice of habitat the species are less narrowly placed than in over-saturated biocenoses. Warm-adapted, polystenothermic groups are to be found in all types of running water in the vast area of the Neotropical plains. They show an enormous degree of differentiation on the species-level. Because of the hundreds of species in many genera of these groups, the systematic study is yet in a rather preliminary stage and makes it impossible till now to ascertain the ...
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