the full-grown larva but their length ratio is different,' e. g., setae 7 and 8 

 are long, especially seta 7, which is several times as long as the claw in 

 some genera (Orthotrichia). 



Pupa. Except for its small size, the pupa of Hydroptilidae does not show 

 any special characters which distinguish it from the pupae of other families. 

 Body spindle-shaped, tapering posteriorly; length of pupae 2.2—5.1 mm. 



Head short; antennae usually short, reaching abdominal segments 3—4, 

 abdominal segments 7—8 in male pupae of some species; first antennal 

 segment with 1—3 small setae. Labrum semicircular or trapezoidal, with 

 one or two pairs of setae near the anterior margin and two setae near the 

 posterior margin; posterolateral setae normally developed; all other setae 

 small, spinelike, sometimes rudimentary (Hy d r o p t i la). Mandibles weakly 

 curved, their apical part flattened, narrow, with a finely serrate, inner 

 cutting edge; outer setae at the base of the mandible situated close together, 

 behind each other, the shorter seta situated more distally and sometimes 

 curved. Wing sheaths pointed and long. Natatorial setae situated on the 

 tarsi of the midlegs, the dorsal row situated on segments 1—3; the ventral 

 row on segments 1—2. Presegmental plates of holding apparatus on 

 abdominal segments 3—7 oval, sometimes oblong and larger than the post- 

 segmental plates, which are situated on segments 3—5; the spinules on the 

 plates are sometimes arranged in regular rows (Figure 490). The part, 

 containing the genitalia of the imago projects slightly at the end of the body. 



The case of the pupa is a slightly modified larval case attached to the 

 substrate by attachment disks made by the larva before pupation. 

 320 Mode of life and habitats. Feeding on algae; living among 

 filamentous algae or plants on stones, in running or stagnant water. 



Distribution. Cosmopolitan. 



Key to Genera 

 Full-grown larva 



1 (2). Very small, 2.2— 3.0 mm long; abdominal segments with dark, 



dorsal sclerites; case slightly dorsoventrally compressed, some- 

 times barrel-shaped, made of secretion and fine sand grains . . . 



7. Stactobia McL. (p. 406) 



Larger, 3.1— 5.5 mm; abdominal segments without tergites; case of 

 different shape. 



Abdominal segments 2—8 with dorsal and ventral median sucker - 

 shaped processes; case made of secretion, sac-shaped, oval . . . 



6. Ithytrichia Eat. (p. 399) 



Abdominal segments without median processes; case of a different 



shape. 



Labrum asymmetrical; second abdominal segment with lateral 



processes; case with deep grooves and ridges on the convex dorsal 



surface; ventral surface flat 5. Orthotrichia Eat. (p.39l) 



6 (5). Labrum symmetrical or slightly asymmetrical only in the 



membranous part; abdominal segment 2 without lateral processes; 

 case laterally compressed. 



350 



2 



(1). 



3 



(4). 



4 



(3). 



5 



(6). 



