primary seta (A), there are 1 or 2 thin, secondary setae (a); the secondary 

 setae L and 1 are situated in the middle of the lateral margin; seta 1 is 

 thinner and shorter than seta L (Figure 395, A, B). The primary anterior- 

 margin seta of the meso- and metanotum retains its positionnear the anterior 

 margin; shorter, yellow, curved, secondary setae are situated near it; 

 2—4 secondary setae are situated near the anterior angle (near the primary 

 seta); a transverse row of 3 primary surface setae, the middle of which is 

 larger than the others, in the middle of the sclerite or slightly more anally. 



Episternum of prothorax complete; epimeron divided; trochantin oblong 

 (except in Oxy e t h i r a), hornlike, with a small distal seta and 2 setules; 

 episternum of meso- and metathorax divided, its anterior part fused with 

 the trochantin and with a short seta (Figures 395, 396); epimeron of all 

 3 thoracic segments with a small seta. 



The ventral sclerotization of the thorax (unlike in the other Annulipalpia) 

 consists of single and paired sclerites, which are present on all or only 

 some of the thoracic segments; presegmentally, the ventral surface bears 

 3 small setules on each side. 



Legs of full-grown larvae of Hydroptilidae (with rare exceptions, e. g., 

 Leiochiton) moderately long or shorter. The forelegs are specialized, 

 in connection with the building activity of the larva, and always shorter than 

 the other legs; hind legs slightly longer than midlegs. Coxae of all legs 

 are broader than the femora and about as long as the femora; trochanters 

 open dorsally; femora of midlegs and hind legs moderately long; they are 

 short on the midlegs, except in I thy t r i c hi a, with a basal process which 

 bears both ventral setae of the femur; fore tibiae with a long, distal process, 

 which bears a complex system of chetae in some genera (A gray lea, 

 Hydroptila, Oxyethira); small distal processes are present in 

 Hydroptila on the mid- and hind tibiae; tibiae and tarsi of midlegs and 

 hind legs long in other genera; tarsi straight, tibiae slightly curved 

 (Figures 467 and 486). Claw long and slightly curved. 



The chaetotaxy of the legs consists only of primary setae which are 

 often strongly modified and form spines (further details in the description 

 of genera and species). Basoventral seta of claw always straight and thin. 



Middle segments of abdomen of full-grown larvae always much broader 

 and higher than head and thorax; first two abdominal segments and the last 

 o-, o two segments smaller than the others; abdominal segment 2 of the larva 

 of Orthotrichia and Ithytrichia with lateral processes which 

 resemble those of abdominal segment 1 of eruciform larvae (which indicates 

 the great age of the group); sides of abdominal segments 1 and 2 of the 

 larvae of Agraylea and Hydroptila with folds. Segments 3— 8 of the 

 larva of Ithytrichia with specific median, dorsal and ventral sucker- 

 shaped processes; dorsum of abdominal segments 1—8 of full-grown larvae 

 (exception Stactobia) membranous; abdominal segment 9 always with a 

 dorsal sclerite; unlike in most Annulipalpia, but as in Rhyacophilidae, 

 Glossosomatidae and Integripalpia, the anus is not a transverse, but a 

 longitudinal slit. Anterior margin of dorsum of abdominal segments 3—7 

 (sometimes also of segments 2 and 8) with unicellular glands characteristic 

 for Hydroptilidae; these glands are remarkable for their large size (up to 

 90 ij. ); similar glands are also present in Orthotrichia and Ithytrichia, 

 on abdominal segment 1, and are arranged in a ring. 



347 



