INSECTS 23 



cleaned piece on a glass slide and examine the outer 

 (convex) surface with the low power of the compound 

 microscope. Look for the boundary lines of many 

 several-sided areas. Each of these areas is called a 

 facet. Each facet is the covering of one of the parts 

 of which the compound eye is composed. 



a. Describe the preparation of the slide for examination. 



b. Describe the shape of each of the facets, and make an out- 



line drawing of three of them, much enlarged, to 

 show the way in which they fit together. 



4. (Optional.) With the aid of a magnifier look for a tiny eye 



in the middle of the front part of the head. There is 

 a similar eye between each compound eye and the an- 

 tenna of the same side. These eyes are simple eyes. 

 Describe the simple eyes as to location, number, and 

 relative size. 



5. Find the upper Up (labrum) on the lower anterior 



part of the head. Describe its location and shape. 



6. (Demonstration.) Raise the upper lip of a large grass- 



hopper and find the jaws or mandibles beneath it. 

 With a dissecting needle gently pry the jaws a 

 little way apart. Do the jaws move from side 

 to side or up and down? 



7. (Optional.) Find the lower lip on the under side of the head, 



i.e. next to the thorax. It is divided vertically into 

 two equal parts. Attached to either side are two 

 tiny, jointed structures called labial palps. 



a. Describe the location of the lower lip (labium). 



b. Describe the position and appearance of the labial palps. 



8. (Optional demonstration.) Between the jaws and the lower 



lip of a large specimen find a pair of appendages each 

 of which is made up of three parts that are joined 

 together at the base : (1) on the outside is a several- 

 jointed feeler or maxillary palp; (2) next is a spoon- 

 shaped body; and (3) a curved and sharp-pointed 



