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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



b), a. smaller intermediate plate (c), and a free apical claw (d) hav- 

 ing its point turned downward and outward. The apical claw has a 

 movement of adduction on the middle plate, and the latter is movable 

 on its hinge with the basal plate. The muscles of this appendage may 

 be studied by cutting the terminal body segment into lateral halves. 

 It is first seen that the base of the appendage is crossed internally by 

 several slender transverse muscles attached on the segmental walls. 

 The muscles inserted on the appendage consist of three flat groups of 



Fig. 41. — Structural details of trichopterous larvae. 



A, metathorax and anterior part of abdomen of Platyphylax dcsignatns. 

 B, posterior abdominal segments of same. C, appendage of tenth segment of 

 same. D, mesal view of right appendage, showing muscles. E, mesal view of 

 terminal appendage of Hydropsychc sp., showing muscles. F, posterior end of 

 abdomen of same, with intestinal processes (ip) extruded from anus. 



a, line of dorso-pleural groove; An, anus; b, proximal sclerite of appendage; 

 Cx, coxa ; d, claw of appendage ; e, f, intersegmental folds between eighth and 

 ninth, and ninth and tenth abdominal segments ; ip, intestinal processes ; LB, area 

 of abdominal limb base ; Pp, pygopod ; Sex, subcoxa. 



fibers (fig. 41 D), all arising on the anterior margin of the basal 

 plate (b). Two of these muscles {la, ib) converge downward and 

 posteriorly to a conmion point of insertion on the inner margin of 

 the base of the apical claw (d), and thus evidently function as ad- 

 ductors of the latter. The third muscle is a broad sheet of fibers 

 {2) lying external to the others, and inserted on the dorsal margin of 

 the intermediate plate (c). Associated with the appendage is a pair of 

 slender, vertical fibers (5) crossing the inner face of the basal plate 

 and attached above and below it to the membranous walls of the 



