Key to Species 

 Full-grown larva 



1 (2). Gills on abdominal segments 2—7; segment 2 without ventral pre- 



segmental gills; western part of European USSR 



1. L. obscurus Hag. (p. 434) 



2 (l). Gills on abdominal segments 2—8; segment 2 with ventral preseg- 



mental gills; Caucasus 2. L. incanus Hag. (p. 435) 



1. Lithax obscurus Hagen 



Ulmer, 1901:309-311, Figures 1- 

 1921:845-848, Figure 303. 



-12; 1903:84; 1909:272, 31 6. - Lestage, 



348 



Full-grown larva. Length 7—8 mm (Figure 592). Dorsal side of head 

 mainly blackish, lighter near occipital foramen. Labrum, with projecting, 

 broadly membranous, anterior margin; setae 3,4, 5, and 6 short, situated on 

 sclerotized part of sclerite, setae 3 and 4 at anterior margin, 5 and 6 in 

 middle of sclerite. Mandibles without teeth, with a median brush forming 

 a row of small chaetoids, and situated at dorsal margin. 



Thoracic tergites (Figure 593) blackish brown, brown, or reddish brown 

 in some places. 



Legs brown, large setae black; claws strongly curved; basal seta strong, 

 situated on a tubercle, reaching apex of claw (Figure 594). 



Abdomen not wider than thorax, 

 slightly tapering posteriorly. 

 Lateral line little differentiated, 

 formed by fine hairs, from seg- 

 ments 3—7. Gills short, filiform, 

 with 2—4 filaments. 



Claw of anal legs strongly 

 curved, with a dorsal denticle. 



Case to 9 mm long, made of sand 

 grains, slightly curved, with 

 flattened ventral side, with large 

 sand grains and small stones 

 laterally, as in A pat a ni a, so that 

 case appears wider, biit less wide 

 than in Silo; posterior end closed 

 by a membrane with a round 

 central hole. 



Pupa. Lengths— 7 mm. 

 Antennae filiform, reaching end of 

 body, proximal segment oblong, 

 larger than others, with a tuft of 

 setules. Labrum with rounded 

 anterior angle. Mandibles small 

 with blunt apex; median margin 

 serrated. 



592 



55« 



595 



FIGURES 592-596. Lithax obscurus Hag.: 



592 - larva, dorsal; 593 - thoracic tergites; 594 - end 

 of tarsus and claw of midleg. Pupa: 595 - anal rods of 

 male pupa; 596 — posterior membrane of case (592 — 

 after Lestage, others after Ulmer). 



434 



