56 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 



// 



sheath of the nerve. Hess (1917) says the hgament in the organs of 

 Cerambycid larvae is probably a connective tissue originating from 

 the hypodermis ; but Eggers (1920) claims that in the thoracic 

 chordotonal organs of adult Lepidoptera it is composed exclusively 

 of tracheal epithelium. The ligament may be long and slender, or 

 it may be reduced in length or lacking entirely; in the latter case 

 the sense cells of the organ are attached to the hypodermis by a few 

 intervening cells, or they rest upon it directly. 



The scolopalse, or sense rods of the chordotonal organs, have been 

 described in the section treating of the sense rods in general (page 

 35). In length they vary from a few microns tO' as much as 23 



CCls 



Fig. 25. — Chordotonal organ of larva of M otwhaiiuiius confusor. in 

 horizontal section of a pleural disc of an abdominal segment (Hess, 

 1917). 



a, wall of pleural disc; b, attachment of cap cells to infolded cuticula 

 at posterior end of disc; c, attachment of chordotonal ligament {d) to 

 infolded cuticula at anterior end of disc ; d, chordotonal ligament. 



microns in different organs ; some are slender and cylindrical (fig. 

 15 F, H, I), others are short (E, G) or bulb-like in form (M). 

 The walls are usually ribbed internally (I, K, r) ; the apical body 

 of the head {AB) is always conspicuous in stained specimens, and 

 the axial fiber (AxF) is attached to it. Often there is no apparent 

 connection between the scolopala and the cuticula of the body wall, 

 but in most organs a distinct terminal fiber (fig. 15, F, fig. 26, t) 

 extends from the apex of the scolopala through the cap cell to the 

 cuticula ; in a few the fiber appears to end before reaching the 

 cuticula. 



