68 A GRASSHOPPER. 



Exercise 4. Clip off a piece of the cornea of a compound eye, clean it on 

 the inside, mount on a slide, study, and draw. 



k) Note the massive, box-like build of the thorax, particularly the 

 second and third segments. Account for these generous struc- 

 tural proportions. Why is the prothorax less heavily built than 

 the meso- and metathorax ? Typically the walls of each segment 

 of thorax and abdomen are made up of four parts a dorsal 

 piece, the tergite, a ventral piece, the sternite, and two lateral 

 pieces, the pleurites. These pieces are not necessarily separated 

 by sutures, or, in fact, by any lines of demarcation. 



1) Look for three impressed lines subdividing the shield of the pro- 

 thorax into an anterior praescutum, followed by a scutum, 

 a scutellum, and a postscutellum in their order. The pleurites 

 of the meso- and the metathoracic segments are also subdivided 

 each into an anterior piece, the episternum, and a posterior 

 piece, the epimeron. Note the blunt spine on the sternite of the 

 prothorax. 



m) Just above the second legs on each side is a little slit-like opening 

 guarded by a pair of lips. This is a spiracle opening into the 

 tracheal respiratory system. Look for other spiracles, one pair 

 on the prothorax and a pair each on certain of the abdominal 

 segments. How many do you find in all ? 



n) Under the bases of the wings on the first abdominal segment is a 

 pair of parchment-like, oval membranes called the ear drums or 

 tympana. Look for similar structures, differently located, in a 

 cricket or a meadow grasshopper. On the anterior rim of each 

 tympanum is the spiracle of that segment. 



Exercise 5. Draw a lateral and a ventral view of the thorax and first 

 two segments of the abdomen on a scale of jour. Label all the parts. 



o) Examine now the tip of the abdomen in several grasshoppers. 

 If it ends in two pairs a dorsal and a ventral of hard pointed 

 projections, the specimen is a female and the projections 

 taken together constitute the ovipositor. By alternately 

 bringing together and spreading the four pieces the female is 



