Submentum trapezoidal, one seta in the anterior angles replaced by a 

 tuft of setae with several longer and thicker setae; cardo and stipes also 

 with secondary setae. Galea short; maxillary palps with short, broad 

 segments. Mentum shining, brown; ventral sclerites with small, thick, 

 light setae; labial lobe with short palps. 



Dorsum of all 3 thoracic segments sclerotized; meso- and metanotum 

 without median suture; their posterior half with a distinct transverse 

 suture, which is a character of the family. Trochantin of meso- and meta- 

 thorax free, not fused with episternum. 



Abdomen slightly flattened dorsoventrally, with numerous small covering 

 setae. Gills of thoracic segments situated at the base of midlegs and hind 

 legs; they are also present on the ventral side on the metathorax; abdominal 

 gills present on segments 1—7 or on segments 1—8, in two pleural and two 

 ventral rows on both sides; each gill forms a small column with an apical 

 tuft of filaments. Anal legs relatively long; dorsolateral sclerite of 

 section "b" with an apical tuft of long, dark, secondary setae. 



Pupa. Length 13—17 mm. Antennae long, reaching end of body in male 

 pupae, slightly shorter in female pupae. Labrum short and broad, with 

 numerous secondary setae. Mandibles long, blades serrated, several teeth 

 larger than the others; a group of setae of varying lengths in the basal part 

 on the outer side. Natatorial setae present only on the mid-tarsi. 



Presegmental plates present on abdominal segments 3—8, postsegmental 

 plates on segments 3—5. Gills present on segments 2—7 in a pleural and a 

 ventral row. Anal rods broad and short, with divided end. 



Pupa lying in a loose grayish sheath; case thick, made of small stones 

 and sand grains. 



Mode of life and habitats. The larvae build chambers and 

 capturing nets with regular square meshes. They occur in running water 

 on the bottom; mainly in rivers and rivulets with many rapids and stony, 

 rubble-covered bottom or bottom covered with large pebbles. 



Distribution. North of the European USSR, West and East Siberia, 

 Amur Region, Maritime Territory, Kamchatka. In addition, northern Europe, 

 China, Japan, India, North America. 



1. Genus Arctopsyche McLachlan 



This is the only genus of the family in the USSR. 



Key to Species of Arctopsyche 



Full-grown larva 



1 (2). Median dark stripe of frontoclypeus slightly concave in the middle, 

 rhomboidal in the posterior part; posterior part of sclerite with a 

 light, distinct, heart-shaped spot contiguous posteriorly with the 

 bifurcation of the frontal sutures. Dorsum of thoracic segments 



with a longitudinal light median stripe 



1. A. ladogensis Kol. (p. 530) 



529 



