BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 179 



are there ? Are there antenna ? Dissect out the month- 

 parts. How do they differ from those of the butterfly ? 

 Are they more like the mouth-parts of the butterfly or 

 more like those of the locust ? 



With fine sharp-pointed scissors make a shallow longi- 

 tudinal incision along the whole length of the dorsal wall. 

 In a freshly-killed specimen a drop of pale greenish blood 

 will issue as the scissors' point is first thrust through the 

 skin. Put a droplet of this blood on a glass slide, cover 

 with cover glass and examine with high power of the 

 microscope. Note that the blood is a fluid containing 

 numerous sub-circular or elliptical bodies, the blood- 

 corpuscles. Note at least two kinds of corpuscles : most 

 abundant a granular, circular kind, the true blood-corpus- 

 cles ; and rarer, a larger, clear, usually elliptical or oval, 

 but sometimes irregular and amoebiform kind, generally 

 spoken of & fat -cells. 



Make a drawing of the corpuscles in the field of the 

 microscope. 



After making the dorsal longitudinal incision pin out 

 the caterpillar in the dissecting-dish with dorsal aspect 

 uppermost. When the edges of the skin are pinned back, 

 the organs most conspicuous in the body-cavity will be 

 the flocculent masses of adipose tissue, the large, simple, 

 tubular alimentary canal usually dark or greenish because 

 of the color of its contents, and the numerous silvery 

 tracJieal tubes. In those caterpillars which spin a silken 

 cocoon, the silk or spinning-glands are usually long and 

 prominent. They lie on either side of the anterior part 

 of the alimentary canal, and open by a common duct on 

 the labium. Rising from behind the middle of the ali- 

 mentary canal maybe found the long, whitish, folded and 

 twisted MalpigJiian tubules. By picking away the fat 

 masses, expose the full length of the alimentary canal. 

 Note its great size (large diameter). Is it divided into 



