NO. 6 



CATERPILLAR AND BUTTERFLY — SNODGRASS 



29 



muscles from the hypopharynx and the labium, which probably 

 regulate the flow of the saliva. 



The silk glands of the caterpillar are a pair of long tubes (figs. 7, 

 8 C, skGld) extending from the head far back into the abdomen. 

 Each gland is thrown into loops and coils, and the slender ducts open 



acsfld. /|V— : Vx 



Spn 



^-7 C jrs.y 



Fig. 15. — Silk glands and spinning apparatus of the tent caterpillar, 



Malacosoma americanum. 



A, The silk glands. B, Section of head lobe formed of the labium, maxillae, 

 and hypopharynx containing the silk press and bearing the spinneret. C, Silk 

 press and ends of ducts, dorsal. D, Longitudinal section of silk press. E, Trans- 

 verse section of silk press. 



acgld, accessory gland ; Dct, silk gland duct ; Hphy, hypopharynx ; Lb, labium ; 

 Lum, lumen of silk press ; Mx, maxilla ; Pr, silk press ; Rph, raphe ; Spn, 

 spinneret. 1,2,3, dorsal muscles of silk press; 4, ventral muscle of press. 



into a small chamber called the silk press (fig. 15 A, Pr), which opens 

 through the spinneret at the end of the labium. A small accessory 

 racemose gland (acgld) opens into each duct near its termination. 



The silk press of the caterpillar is clearly the salivarium of other 

 insects, which has been converted into a closed chamber by the union 

 of the hypopharynx with the basal part of the labium (fig. 5 E, Pr). 

 The salivary muscles are strongly developed (fig. 15 C), three pairs 



