A GRASSHOPPER 13 



Exercise 8. With strong forceps remove the dark-colored mandi- 

 bles and draw the inner surface of one of them on a scale 

 of 5. 



Exercise 9. Remove the maxillae, which lie just back of the 

 mandibles, being careful to take out the entire structure. 

 Mount them on a glass slide in glycerine or water with 

 the posterior side uppermost, and examine them under the 

 microscope. Note the following parts : the basal segment 

 or cardo, by which the maxilla articulates with the head; 

 the stipes, the broadest segment of the structure ; the 

 inner and the outer lobes, which project from the distal edge 

 of the stipes ; and the maxillary palp, which projects from 

 the lateral edge of the stipes. Draw a maxilla on a scale 

 of 5 and label all of these parts. 



Exercise 10. Note between the maxillae and just in front of the 

 labium a median projection, the hypopharynx. Remove 

 the labium, taking care to leave none of it in the animal, 

 mount it on a slide, and identify the following parts : 

 the basal segment or submentum, by means of which the 

 labium articulates with the head ; the mentum, the succeed- 

 ing segment; the ligula, which projects from the distal 

 edge of the mentum ; and the two labial palps, which project 

 from the lateral edges of the mentum. The labium is a 

 second pair of maxillae fused in the median line. Trace 

 the homologies between the parts of the labium and those 

 of the maxillae. Draw the labium on a scale of 5 and 

 label its parts. 



The mouth-parts of the wasp and the beetle. The mouth-parts 

 of the grasshopper are called biting mouth-parts because the 

 insect bites or chews its food instead of licking or sucking it. 

 Biting mouth-parts characterize all the more primitive insects. 

 The mouth-parts of the beetle are similar to those of the grass- 

 hopper, although the former is a much higher insect. 



