As in the scheme of Ross (1956:10, Plate 1 ), the lower Paleochaetoidea 

 (Rhyacophilidae, Glossosomatidae and Hydroptilidae) have an intermediate 

 166 position between the Annulipalpia and Integripalpia; this classification is 

 based on the fact that the larvae of these lower Annulipalpia have retained 

 some ancient characters in common with the Integripalpia. The other 

 part of the scheme consisting of the higher Paleochaetoidea and all 

 Neochaetoidea differs from the scheme of Ross; it expresses a different 

 point of view on the systematic structure of the suborder and the phylo- 

 genetic relationships between the families. 



The phylogenetic scheme is based on the foregoing data and systematic 

 data; the main characters used are the morphological characters of the 

 larvae, the degree of primitiveness or specialization, especially of the 

 chaetotaxy, method of feeding, the character of built structures, and the 

 position in the system in the light of known phylogenetic relationships 

 between the family groups. The relative size of the groups is shown by 

 the thicker or thinner branches based on the data given by Fischer (1944) 

 until 1938, with some modifications based on later data (see p. 1 31 ) . 



We suggest that the primitive larva of the ancestors of the order was 

 a small campodeiform larva with a simple primary chaetotaxy, with simple 

 legs of similar form, and without gills, which resembled remotely the 1st- 

 stage larvae of the recent Rhyacophilidae or Hydroptilidae; this larva had, 

 like the Hydroptilidae, small sclerites on the dorsum of the abdominal and 

 thoracic segments. 



It is not important whether this primordial form was microphagous and 

 lived in immovable, attached tubes like the larvae of the recent Phylopo- 

 tomidae and Psychomyiidae, or lived freely, with a different type of 

 phytophagous life. We are interested in the trends of primary divergence 

 of the larvae of the ancestors of Trichoptera; one of these trends (stem i) 

 resulted in the further development of the inhabitants of immovably 

 attached shelters; the second trend (stem II) resulted in the development 

 of free-living forms, most of which built portable cases. Development of 

 the first trend resulted later in the appearance of very mobile micro- 

 phagous and predatory forms; development of the second line resulted in 

 the development of a large group of sluggish case bearers. The structures 

 of Trichoptera which are attached at one place necessitate that their 

 inhabitants be mobile; the bearing of a case which is often bulky restricts 

 the mobility of the larva. 



Evolution along stem I diverged in 2 lines: line 2 is the conservative line 

 of development in which the primary method of feeding (microphagy) and the 

 life in simple tunnel- shaped tubes were retained; line 1 is a progressive 

 line connected with a change to a predatory life and with the transformation 

 of the simple tunnel- shaped tubes into complex capturing structures. 



The evolution of families along line 2 was reduced to the improvement 

 of the organs collecting food from the walls of the tube and ensuring the 

 building activity of the larva. In the recent fauna, evolution along branch 2" 

 resulted in forms with a membranous labrum characteristic for the larvae of 

 Philopotamidae (with a rudimentary dorsal sclerite at the base) or in forms 

 with an elongate head and broad, short labrum with a dense brush of hairs 

 at the anterior margin characteristic for the larvae of Stenopsychidae; in 

 the recent fauna, evolution along branch 2' resulted in the appearance of the 



5724 156 



