THE LOCUST OR THE CRAYFISH. 63 



see any advantages coming from this position, rather than 

 further back or more ventral ? Compare the wings with the 

 legs. Are they made up of joints as the legs are? Com- 

 pare the front and rear wings as to structure. Examine 

 under lens and draw both wings, showing size, shape, the 

 position and branching of the "veins" or ribs. How do the 

 front and rear edges of the wings compare? Of what value 

 is the difference? 



Look carefully over the abdominal segments, particularly 

 the posterior ones. Do you find anything suggesting 

 appendages ? Are they the same in all specimens ? Can you 

 suggest their function? See text-books. 



Examine carefully the whole mouth region, first with a naked 

 eye and then with a hand-lens. Watch the mouth parts in 

 action. Move the various structures with a needle. Are 

 the structures paired or median or both ? Describe the parts 

 in front of the mouth; behind the mouth; at the sides. Make 

 a diagram with the mouth in the center and the parts 

 grouped about it and far enough apart to enable you to 

 show their relation, as you understand it. What is the part 

 played by each in eating ? Mention the points at which the 

 mouth parts appear to you well adapted to the kind of food 

 used by the locust. 



Compare your drawing with figures in the reference books 

 for the names of the various mouth parts. Are they seg- 

 mented like the legs? Are there any other paired append- 

 ages about the head? If one pair of jointed appendages 

 represents a segment of the body, how many segments in 

 the head of the locust ? 



c. The Sense Organs. The antennae. What is their position? 

 Are they segmented? What do you believe to be their 

 function ? Evidences. 



The eyes. These are not appendages in the same sense as 

 the antennae, although they are paired. Note their exact 

 situation and size. Examine their surface with a lens. 

 Estimate the number of facets. With is the shape of each 

 facet ? Why this shape ? What does each facet signify (see 

 descriptive texts) ? Estimate again the amount of the whole 

 surroundings commanded by the two compound eyes. There 

 are also three simple eyes (ocelli). Find them. Make a 

 drawing of the head from the front view, showing the 

 structures studied. 



