FIGURE 334. Philocrena trialetica Lepn. Anal legs in different positions 



Segment 9 (Figure 332) without lateral processes, but not narrower than 

 the posterior part of segment 8. Dorsal sclerite brown, broad, with blackish 

 brown anterior margin; it is dark brown where chetoids are numerous; a 

 wide process in form of an Ancylus shell with the apex posteriorly in the 

 middle; this process has groups of large indistinct spots without setae at the 

 anterior margin and laterally. Anterior-margin setae of segment 9 small 

 and thin, situated on a membrane near the black margin; medioanal setae 

 short, light brown, thin and situated at the posterior margin, lateral to the 

 median tubercle; intermediate and lateral setae situated close together, 

 at a distance from the medioanal seta; anterior -angle seta light brown, 

 short, situated laterally, in a row with the anal setae. The 3 ventral setae 

 large, dark and strong, situated on a convex brown sclerite; lateral and 

 intermediate setae situated at the sides of the segment. 



Anal legs (Figures 332 and 333) very long and highly specialized. Dorso- 

 lateral sclerite yellow, with a broad, black, median border and a narrow, 

 basal border; sclerite divided by grooves into three parts: a divided, basal 

 part, a lateral part and a distal part; each part with groups or rows of dark 

 reddish brown spots; these parts bear numerous dark chetoids, Unlike in 

 Rhy a cophila, there are two basoventral hooks: the first is homologous to 

 the hook of species of Rhy ac ophila; it is situated in the angle of the 

 sclerite, very large (Figure 334), and with a black border at the base and 

 a reddish brown end; second hook much smaller, situated on the median 

 side of the dark basoventral plate which bears a short, light seta and a 

 small, outer, beak- shaped process. Dorsal tubercle of distal part of the 

 sclerite with a rounded apex directed toward the side of the claw; this 

 tubercle has a dark basal border; both setae of the distal part are short 

 and light, one situated on the outer side and the other medially; 3rd seta 

 of sclerite (unlike in Rhyacophila) not situated in the basal part but in 

 the dorsal angle of the lateral part, also short, yellowish brown and curved. 

 Ventral plate of sclerite "c" brownish yellow, with a black median border; 



315 



