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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



The Corydalus larva differs from the Sialis and Chauliodcs larvae 

 in that the basal lobes of the first seven abdominal appendages bear 

 each a large ventral tubercle supporting a circle of respiratory fila- 

 ments (fig. 36 B, Vs). When the filaments are removed it is seen that 

 each tubercle is subdivided distally into three terminal lobes (C, Vs), 

 and dissection reveals the fact that the tubercle is provided with a large 



Fig. 36. — Thoracic and abdominal appendages of the larva of Corydalus 

 coniutus. 



A, transverse section through anterior end of metathorax, showing subcoxal 

 lobes (Sex) above bases of coxae (Cr), and levator and depressor muscles of 

 trochanter (O, Q) arising in coxa. 



B, last four segments of abdomen, showing segmental appendages. 



C, transverse section through posterior part of an abdominal segment, seen 

 from behind, showing limb base lobes (LB) supporting each a stylus (Sty), 

 and a retractile gill-bearing tubercle (I's). 



D, section through base of riglit abdominal appendage and gill tubercle, seen 

 from behind, showing muscles of stylus and gill tubercle. 



E, antero-mesal view of right appendage (pygopod) of tenth abdominal 

 segment. 



F, section of terminal appendage, showing insertion of retractor muscles 

 behind bases of claws. 



Cx, coxa; d, claws (crochets); c. insertion point of retractor muscles of 

 claw-bearing tubercle (planta) ; /. lateral body muscles; LB, limb basis; O, 

 (J, muscles of trochanter; rvs, retractor muscle of gill-bearing or claw- 

 bearing lobe of appendage; Sex, subcoxa; sinels, muscles of stylus; Sp, spiracle; 

 Stn, sternum; Sty, stylus; T, tergum ; J's, retractile lobe of appendage (retrac- 

 tile vesicle). 



retractor muscle (C, D, rvs) arising on the dorsum of the segment and 

 inserted by three diverging branches on the distal surfaces of the three 

 terminal lobes of the tubercle. The gill tubercles are thus highly 

 suggestive of the eversible sacs of the thysanuran appendages, except 

 for the difference that their retractor muscles arise on the terpal 



