10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



traversing the thorax from the sucking pump in the head to the an- 

 terior part of the abdomen, where it joins the stomach, or ventriculus 

 (Vent). Just before the stomach the oesophagus bears dorsally a 

 diverticulum in the form of a thin-walled vesicle (Ves), which has 

 been supposed to be a reservoir for liquid food, but generally it is 

 found to contain air. The very short ventriculus has no caeca, and its 

 walls are thrown into circular folds. Following the ventriculus is a 

 long, slender intestinal tube (alnt), which opens into the under side 

 of a large rectal sac (Red). In a peach borer moth (B) the alimentary 

 canal is an even more slender tube, except for the oesophageal diver- 

 ticulum and the rectal sac. The alimentary canal of the monarch 

 butterfly Danais plexippus, as described by Burgess (1880) under 

 the name archippus, and recently figured by Ehrlich and Davidson 

 ( 1961 ) differs in no essential way from that of the moths, though the 

 oesophageal diverticulum is half or two-thirds the length of the 

 abdomen. According to Burgess the delicate walls of the diverticulum 

 are well supplied with slender longitudinal and transverse muscle 

 fibers, but the sac contains nothing but air. 



Long coiled glands opening by a common duct at the base of the 

 labium have been described or figured in various adult Lepidoptera 

 (see Schmitt, 1938; Srivastava, 1957; Ehrlich and Davidson, 1961). 

 These glands have replaced the larval silk glands, and are presumably 

 salivary in function. In the honey bee larva the silk glands completely 

 break down after spinning, and the salivary glands of the adult are 

 regenerated from anterior remnants of the larval ducts. 



The Malpighian tubules arise from the anterior end of the intestine 

 as a pair of tubes varying in length, in some species swollen into 

 bladderlike vesicles. Each primary tubule divides into two, and 

 usually one of these again divides, giving three tubules in all on each 

 side. The tubules may form a tangled mass around the stomach and 

 the intestine, and in some species at least their posterior ends are 

 inserted beneath the muscular coat of the rectum. 



It is clear that the basic specialization of adult Lepidoptera is a 

 structural adaptation for feeding on nectar contained in the depths of 

 flower corollas. That sugars are their only food is evident from their 

 lack of digestive enzymes other than invertase. Though nectar was 

 formerly a favorite drink of the gods, it must be a very inadequate 

 diet even for a moth or butterfly. The female at least needs proteins 

 for the production of yolk-filled eggs. Hence it should be the duty 

 of the caterpillar to store up food reserves in its body to supplement 

 its diet in its own adult stage. The tent caterpillar moth, Malacosoma 

 americanum, is a species that takes no food in the adult stage, but 



