145 to the group Hyper rhyacophila Dohler (the larvae of which have 

 abdominal gills which form a conical style with longitudinally arranged 

 filaments) belong Rh.torrentium (Europe) and Rh. vie aria (Caucasus); 

 Dohler (1950:276) placed R h. albardana (Europe) in the same group. 

 To the group Rhyacophila s. str. belong numerous species, the larvae 

 of which have gills which form a tuft of filaments on the apex of a short 

 style; these include the European species Rh. vulgaris, Rh. dorsalis, 

 Rh. obliterata, R h. septentrionis, Rh. hageni, Rh. nubila, 

 Rh. fasciata, Rh. aurata; they include the Caucasian species 

 Rh. subnubila, Rh. subovata and Rh. cupressorum. 



In spite of the few data on the larvae of Rhyacophila there is a connec- 

 tion between the distribution of the groups and the characters of the larvae. 

 It follows from the foregoing data that most of the groups of Ross ' s species 

 have conservative larvae- in which they change little through all 5 larval 

 stages; the full-grown 5th-stage larva of these species closely resembles 

 the 1st -stage larva, and belongs to the primitive type Hypo rhyacophila. 

 The distribution of the groups with larvae of the Hyporhyacophila type 

 is wide, almost as wide as the distribution of the whole genus Rhyacophila. 

 According to Martynov(l 924a: 357 -373), the genesis, original habitats and 

 center of distribution of the genus Rhy a c op h i 1 a (as that of many other 

 groups of Trichoptera in the northern zone) were in Angara; Angara was con- 

 nected with North America by the Bering Bridge, and its western part was 

 for a long time separated from Europe by an arm of the Turgai Strait. ** 



Most of the recent Asian and American species of Rhyacophila have 

 larvae of the primitive type Hyporhyacophila; this type should be 

 considered the ancient type of larvae of the Rhyacophila (closely related 

 to the primordial type), and is most widely represented in the recent fauna 

 in the Asian- American group "s ibir i c a, "t and in other American, Asian 

 and smaller American-Asian groups of Ross. The larvae of the 

 Mesorhyacophila type are closely related to the primitive type but 

 have more complex anal legs; they sometimes also have thoracic gills and 

 are present in 3 species from central Asia, southern Siberia, the Ussuri 

 territory, Japan and in 4 North American species. Single species with a 

 larva of the Pa 1 e o r hy a c op hi 1 a type (closely related to Hyporhya- 

 cophila but with tufted abdominal gills) are known from Japan and 

 Sakhalin (Rh. hokkaidensis) and from North America (R h. a c r o p e d e s). 

 Species with larvae of a higher type, i. e., of the Pararhyacophila, 

 Hyper rhyacophila and Rhyacophila s. str. type of the group 

 "vulgaris," are absent in America and Asia. 



The European species of Rhyacophila were considered by Martynov 

 (ibid.) as descendents of the ancient immigrants from Asia which entered 

 Europe from Asia by the southern route of immigration after the formation 

 of the Turgai Strait and the northward regression of the sea. These ancient 

 immigrants from Asia and Europe became isolated in Europe in later 

 geological periods by the development of the deserts in Central Asia and the 

 repeated transgressions of the Caspian Sea; they developed independently 

 in Europe. A remarkable feature of this evolution is the early differentiation 

 of a very progressive branch which resulted in the appearance in the recent 



* This can be judged by the species of some groups, the larvae of which are known. 

 ** Following Borisyak, Martynov (1924a:732) called this boundary the Ural "Sea." 

 t Ross (1956) wrongly considers the Caucasian species Rh. abchasica as a Siberian species (Martynov, 

 1934:61). 



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