INTERNAL ANATOMY OF THE GRASSHOPPER 1 



1. Secure a large preserved Grasshopper and with scissors cut off the 

 wings and the legs, close to the body. Pin the specimen, dorsal surface 

 up, in a wax-bottomed pan, and cover with water. Carefully insert the 

 tips of sharp-pointed scissors through the dorsal body wall, in the midline, 

 at the extreme posterior end of the abdomen. Make a median longitu- 

 dinal incision extending from the point of insertion throughout the length 

 of the abdomen and the thorax. Be careful to cut just through the body 

 wall so as not to injure the underlying tissues. Carefully separate the 

 cut edges and then pin in such a way as to hold them apart. 



2. Examine the internal organs and note the large alimentary tract 

 running throughout the length of the body. The following parts may be 

 noted: (a) the tubular esophagus extending from the mouth into the 

 thorax, where it gradually enlarges to form (b) the crop. Note (c) the 

 salivary glands extending along the wall of the crop anteriorly to the 

 mouth cavity into which they open. Posteriorly the crop narrows to 

 form (d) the muscular gizzard (proventriculus) which leads in turn to 

 0) the rather small stomach (ventriculus). Opening into the anterior 

 end of the stomach are (/) the gastric caeca. 



3. Posterior to the stomach a mass of fine, coiled malpighian tubules, 

 which are excretory in function, obscure the underlying intestine, into 

 the anterior end of which they open. In the posterior part of the abdo- 

 men, the enlarged portion of the intestine (rectum) continuing to the 

 exterior is covered by a pair of gonads which he close to the dorsal body 

 wall. Trace the intestine to the anal opening. 



4. Make a drawing of the internal anatomy which will show the struc- 

 tures observed in the preceding paragraphs. 



5. After carefully cutting anteriorly and posteriorly, remove the entire 

 alimentary canal and attached structures from the body, but leave the 

 gonads in place. Find the duct leading from one of the gonads and trace 

 it ventrally to the point where it unites with the duct from the other 

 gonad and forms a common duct to the exterior. 



6. Note the large leg and wing muscles in the thorax. With the 

 forceps remove a small piece of muscular tissue, mount and examine 

 microscopically in order to find some of the widely distributed air tubes 

 (tracheae) which are abundant in the muscle tissue. Note the relation 

 existing between spiracles and tracheae along the abdominal wall. 



7. Examine the ventral body wall and find the median nerve cord 

 extending the length of the body in the mid-ventral fine. Note its general 

 nature and also the enlarged nerve centers (ganglia) distributed along 

 it ; two of which are in the head, three in the thorax, and five in the abdo- 

 men. Make a drawing to show the structure of the nervous system. 



1 B. pp. 117-123. 

 297 



