56 STUDIES OP ANIMAL LIFE. 



B. General Observations. 



1. Observe that the "shell " of the grasshopper is much 



lighter and more flexible than the shell of the 

 crayfish. Why is this necessary ? 



2. What sort of a background will make the grass- 



hopper difficult to be seen ? 



3. Identify three distinct regions of the body, — head, 



thorax and abdomen. 



4. Why is the grasshopper said to have three regions 



to the body and the crayfish only two regions ? 

 As compared with the crayfish, in which of the body 

 regions has there been the greatest differentiation ? 



C. The Head and its Appendages. 



1. What is the shape of the head ? (Make sketches.) 



2. Is there a " neck " ? 



3. In what direction is the head movable ? 



What advantage is gained by its being movable in 

 this direction ? 



4. The Eyes. 



a. What is their position ? 

 h. Are they " compound " ? 



c. Ocelli. These are three very small, simple 



(single) eyes. One is situated in the middle 

 of the forehead and one just above each 

 antenna. 



d. Compare the grasshopper's range of vision with 



that of the crayfish. 



e. Make a sketch to show the position of the eyes. 



5. The Antennae. 



a. Observe their position, shape and segmentation. 



h. Are they movable ? 



c. Compare in structure with those of the crayfish. 



