FIGURES 8 and 9. Nota: 



8 — pronotum of Rhyacophila obliterata (after Kachalova); 9— meso - 

 notum ofEcnomus tenellus. 



The secondary chaetotaxy is often very rich and makes the above- 

 described arrangement less clear; the primary setae are usually 

 distinguished by their greater thickness and length. 



The pleural region of th,e- thoracic segments forms pillarlike or irregular, 

 ventrally directed, short processes to which the legs are attached. The 

 following sclerites of the pleural region serve for the articulation of the legs: 

 22 episternum, epimeron and trochantin, which are together called the pleuron.* 

 The primary chaetotaxy of the pleuron consists of one seta on the epimeron, 

 situated on the sclerite or close to it on the membrane, and of one seta or 

 2 setules on the trochantin; the episternum does not bear a primary seta. 

 The trochantin of the prothorax is of a different form and bears a distal 

 process; in some genera of Aethaloptera this process is very long. The 

 trochantin of the meso- and metathorax forms a small plate which is usually 

 fused with the episternum and is rarely free; the primary seta of the fused 

 trochantin is situated on the boundary with the episternum and is often 

 arbitrarily named (also in the present book) the seta of the episternum; the 

 trochantin of both the meso- and metathorax is rarely free. 



A ventral sclerotization of the thorax of some groups (Rhyacophilinae) 

 is completely absent; in a number of groups of Annulipalpia (Glossoso- 

 matidae, Hydropsychidae) the prosternum is well developed, and covers 

 the ventral surface of the segment completely or almost completely; in the 

 Hydroptilidae, all three thoracic segments bear median sternal sclerites; 



* The name "supporting plate" (in German "Stiitzplattchen" and in French "plaque d'appui") was widely 

 used in keys and in the literature in the past for the sclerites of the pleural region. This name is not used 

 any more. Lloyd (1921:9, 11) states that "the 'supporting plate' of the larvae of caddis flies is the 

 episternum and epimeron." The literature of the 1930's on the comparative morphology of insects 

 classified this point (Snodgrass, 1935:161—166); for information on the morphology of the thorax of larvae 

 of caddis flies, see Nielsen, 1942:292—296. A list of the old and new terms used in the description of the 

 larvae of caddis flies has been given by Lepneva (1949:162). 



18 



