THE CATERPILLAR AND THE MOTH 



The fresh silk is a liquid formed in two long, tubular 

 glands extending far back from the head into the body of 

 the caterpillar (Fig. 1^4, SkGI). The middle part ot each 

 tube is enlarged to serve as a reservoir where the silk 

 liquid may accumulate (Fig. 155 A, Res); the anterior 

 narrowed part constitutes the duct (Del), and the ducts 



Fig. i$$. The silk glands and spinning organs of the tent caterpillar 



A, the silk-forming organs, consisting of a pair of tubular glands (G/, G/), each 

 enlarging into a reservoir {Res), and opening through a long duct (Dct) into 

 the silk press (TV), with a pair of accessory glands (glands of Filippi, GIF) opening 



Into the ducts 



B, side view of the hypopharynx (Hphy) with terminal parts of right maxilla 

 (Mx) and labium {Lb) attached, showing the silk press {Pr), its muscles, and 

 the ducts {Dct) opening into it, and the spinneret (Spt) through which the silk is 



discharged from the press 



C, upper view of the silk press {Pr)> showing the four sets of muscles (Mcls) 



inserted on its walls and on the rod-like raphe (Rph) in its roof 



D, side view of the silk press, spinneret, raphe, and muscles 



E, cross-section of the silk press, showing its cavity, or lumen {Lum), which is 



expanded by the contraction of the muscles 



[287] 



