Key to Species 

 Full-grown larva 



1 (2). Dorsal side of head with a crown of secondary setae 



3. D. discolor Ramb. (p. 399) 



2 (l). Crown of secondary setae on dorsal side of head absent. 



3 (4). Setae 15 and 16 about the same length. Posterior median of tergites 



of metathorax oblong. Pre segmental gills of abdonninal segment 2 



and gills on segment 8 present; Caucasus 



1. D. caucasicus Ulm. (p. 390) 



4 (3). Seta 16 much shorter than 15. Posterior median tergites of meta- 



thorax triangular. Presegmental gills on segment 2 absent; seg- 

 ment 8 without gills; southeastern part of the European USSR near 

 the Carpathians 2. D. trifidus McL. (p. 396) 



310 1. Drusus caucasicus Ulmer 

 Martynov, 1926:45. 



Full-grown larva. Length 10—12 mm. Head (Figure 540, A) wide, dark 

 brown dorsally, yellowish brown near occipital foramen and ventrally. 

 Integument reticulate, with small spinules (Figure 540, B). Eyes on light 

 periocular area; antennae situated far from eyes near ridge. Fronto- 

 clypeus large, wide anteriorly; ends of frontal sutures slightly curved; 

 anterior part punctate,''' posterior part with triangular pattern of large dots 

 situated behind 2 pairs of smaller dots. Area of dorsal stripes occupied 

 by rows of 3—5 small dots, and groups of dots lateral to coronal suture; 

 short rows of dots on area of lateral stripes. Ventral surface with groups 

 of light brown dots on light background posteriorly (Figure 540, C). 



Anterior-margin setae of head large; median and intermediate seta dark, 

 lateral seta light, curved inward; anterior frontal seta the same; middle 

 frontal seta dark, large; posterior frontal seta thinner, light, small; seta 7 

 dark, short, situated near ridge before antenna; seta 9 black, situated medially 

 to eye, moderately long; seta 11 small, light; seta 10 light, situated near 

 margin of periocular area; setae 12, 13, and 14 forming a transverse row 

 behind periocular area, 14 black, longest on the head; 13 small, light; 12 thin, 

 short, brownish; setae 15 and 16 situated close together, 15 thin, moderately 

 long, 16 similar, lighter, projecting; seta 17 situated near fork of frontal 

 sutures, large, dark; ventral seta 8 small, situated near anterior margin, 

 seta 18 very small, situated on light background. 



Dorsal sclerite of labrum (Figure 540, D) dark brown, tuberculate, with 

 broad median indentation; posterior-angle sclerites with dark basal spot; 

 anterior margin membranous, with large median process; seta 1 situated on 

 each side of process, in form of small, thick, blunt transparent spine; seta 2 

 represented by a much larger, light spine near anterior margin, curved, 

 blunt, thick; seta 4 the same; seta 3 short, light, situated near margin; 

 setae 5 and 6 yellowish, larger than others, situated lateral to median pit. 



Mandibles (Figure 540, E) mainly black, reddish brown distally, spadelike, 

 without teeth, except for a small, blunt, distal process on dorsal margin; median 

 brush situated at dorsal margin formed by dense, yellow chaetoids; lateral setae 

 situated basally, light, yellowish brown, dorsal seta larger than ventral. 

 * Described from preparations; the dots are indistinct in the whole larva. 



390 



