THE GRASSHOPPER. 17 



Stick one pin through the tip of the abdomen, and 

 another through the femur of each hind leg. Cut with 

 scissors just through the body wall, along each side 

 of the body from the tip of the abdomen to the head. 

 With forceps, lift the flap between the cuts, scraping 

 away the tissues below it with the scalpel. Study. 



2. Find the air sacs along each side. How many? 



3. Find the air tubes, or tracheae. Trace them to 

 the spiracles. 



If the grasshopper has been preserved in alcohol, 

 the tracheae and air sacs will not show very plain ; 

 but in a freshly killed specimen they will be filled 

 with air and will show as silvery white tubes. 



4. Find the large muscles in the thorax that move 

 the wings. 



5. If your specimen is a female, see the ovaries 

 and the eggs. How many eggs? How arranged? 

 What shape? 



6. Trace the oviduct from the ovaries to the 

 ovipositor. 



7. Thrust a blunt probe into the mouth. It passes 

 through the oesophagus into the crop. 



8. Find some double cone-shaped pouches just be- 

 hind the crop. These are the gastric caeca. How many? 



9. Find the stomach. 



10. Trace the intestine. 



11. Draw the alimentary canal, showing oesopha- 

 gus, crop, caeca, stomach, and intestine. 



12. Notice in the body many small red threads. 

 These are the urinary tubules. They are excretory 

 organs. 



13. Carefully remove the digestive organs and 

 look for the nervous system lying along the floor of 

 the abdomen. Trace it through the thorax. 



14. Is the nerve cord double or single? Find lit- 

 tle knots (ganglia) on the nerve cord. How many 

 ganglia in the abdomen? How many in the thorax? 



