A Lepidopterous Insect. 125 



The Circulatory System. The heart will be observed 

 as a median tube extending along the mid-dorsal line of the 

 animal, immediately below the integument. The blood, 

 which contains amoeboid corpuscles, enters the organ through 

 certain lateral ostia, and is forced anteriorly, where it enters 

 the aorta, from whence it is distributed to the various 

 sinuses of the body. 



The Muscular System. Many parallel bands of mus- 

 cles, segmentally arranged, will be observed immediately 

 under the integument. In the head they become specially 

 developed in the neighborhood of the mouth parts. 



Remove the heart and the laterally lying muscle bands. 

 The body-cavity will be found to be apparently filled with the 

 subdivisions of \hzfat-body, though more careful examination 

 with a lens will reveal the presence of other organs of some- 

 what the same appearance. 1 



The Digestive System. The mesenteron or stomach 

 will be observed as a large, rather thick-walled cylinder extend- 

 ing antero-posteriorly through the body-cavity. Followed 

 anteriorly, the stomach is found to lead from a thinner-walled 

 oesophagus. Posteriorly, the stomach becomes abruptly con- 

 stricted and passes into the intestine, which in turns opens 

 through the rectum to the exterior. The salivary glands will 

 be found lying anteriorly, along the sides of the oesophagus. 

 Their ducts open into the mouth. Associated with the sali- 

 vary glands are the silk glands or s eric tar ia, a pair of elon- 

 gated organs which may be found lying side by side along 

 the lower surface of the anterior portion of the mesenteron. 2 



1 The substance of the fat-body is loose and flocculent. 



2 Both salivary and silk glands are elongated tubular organs. Each 

 salivary gland extends as a coiled thread from the dorsal region of the 



