4. Genus Chimarrha Stephens 



Full-grown larva. Length 7—8 mm. Anterior margin of frontoclypeus 

 with a deep asymmetrical indentation. Coxa of forelegs with a large, 

 massive spinelike process distodorsally. Abdomen white or pale yellow. 



Mode of life and habitats. Rivulets with clean cool water and 

 rapid current; on stones. 



Distribution. West of the European USSR (Karelia, Latvia, Lithuania) 

 In addition, Europe, Africa, southern Asia, Philippines, North and South 

 America, Australia. 



1. Chimarrha marginata Linne 



Marlier, 1943a:l— 8, Figures 1—8. 



Full-grown larva (Figure 517). Length 6.0—7.5 mm. Form of body as 

 in Wormaldia. Head oblong, amber yellow, darker than in Wormaldia, 

 but not as dark as in Philopotamus; anterior margin of frontoclypeus 



377 brownish, deeply asymmetrically indented in the middle; left margin of 

 indentation projecting further than right margin; eyes as in Wormaldia, 

 situated at a distance from the anterior margin. 



Labrum dor sally (Figure 518) as in Philopotamidae, membranous in 

 its greater part; lateral ligulate processes, which are curved ventrally 

 when the insect retracts the labrum near the anterior margin; a row of 

 small straight hairs at the anterior margin; ventrolateral tufts of hairs 

 smaller than in Wormaldia and Philopotamus. Mandibles 

 (Figure 519) brown, massive; upper blade (except the small distal part) 

 reduced; apical tooth of left mandible pointed; 2 smaller subapical teeth; 

 right mandible with blunt apex and with a pointed subapical tooth; median 

 margin of lower blade of both mandibles serrated; outer setae long, 

 situated behind each other, slightly away from the basal margin. 



Pronotum brown, lighter than head; posterior margin and basal part of 

 lateral margin with a broad dark border (Figure 517). 



Legs light yellow; forelegs slightly shorter and thicker than the others; 

 midlegs and hind legs of almost the same length. Coxa of forelegs short 

 (Figure 520); dorsal articular process black; with a larger anterior spine- 

 like process with a strong, black, short, primary seta dorsally; basoanterior 



378 seta also short and strong. Claws of legs slightly curved; a pointed spine 

 near the basal seta. 



Abdominal setae small, black, well marked. Five anal gills. 



Anal legs short, simple; claw as in Wormaldia, strongly curved and 

 slightly larger. 



Pupa. Length 5—7 mm; form of body and length of antennae as in other 

 Philopotamidae. Labrum broadly rounded (Figure 521 ); median process 

 broad, little marked; a short black seta near the anterior margin; 2 strong, 

 dark, long setae laterally on the labrum. Mandibles (Figure 522) as in 

 Wormaldia, dark brown, sharply curved at the base, straight in the other 

 part, pointed; medial subapical process with 2 small denticles; median 

 blade finely serrated apically and basally to the process. 



Wing sheaths short and pointed; mid-tarsi with dense natatorial setae; 

 claws strong, strongly curved, dark at the end. 



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