A GRASSHOPPER. 67 



suture between the second and third somites. Save all the parts 

 for study with the dissecting microscope. The wings and legs may 

 as well be cut from the other side also } as they are only in the way. 



g) Under the lens the head is seen to be made up of a number of plates 

 or sclerites joined at fixed sutures. The largest of these plates 

 is the epicranium. It forms the top and front of the head and 

 extends on the sides to the cheeks or genas. Below it is bordered 

 by the clypeus. 



Exercise 2. Draw the front of the head on a scale of five or six. Label 

 all the parts, some of which are named in "ti)." 



h) In working out the mouth parts begin with the upper lip labrum 

 attached to the lower border of the clypeus. Raise it with the 

 dissecting needle and disclose a pair of strong, dark-colored jaws, 

 the mandibles. Move these back and forward. Do they work 

 horizontally or vertically ? Note the toothed edge. With scissors 

 and forceps carefully remove labrum and mandibles and place 

 them in a watch glass. Disregarding a brown, tongue-like organ, 

 the hypopharynx, remove next the maxillae, a second pair of 

 jaws, and finally the lower lip or labium. Save these also. 



i) Mount the labium and the maxilke on separate slides and study 

 with a low power of the compound microscope. Note, in the 

 labium, a basal piece, the submentum. Beyond this is the 

 mentum, from the distal end of which projects the ligula. From 

 each side of the mentum arises also a palpus. 



j) The basal segment of the maxillae is called the cardo. Next comes 

 a broad piece, the stipes, which terminates in a toothed, cutting 

 lacinia. A spoon-shaped piece galea serves as a covering 

 for the lacinia, and to one side of this is a palpus. Compare the 

 labial with the maxillary palpi. 

 How many pairs of appendages have we found in the head ? Which 



of the mouth parts are not paired appendages ? Is there any evidence 



that the labium is made up of a pair of appendages ? 



Exercise 3. Draw the labium y one of the maxilla and one of the mandibles 

 on an enlarged scale. 



