180 ARTHROPODA. 



on all parts of the body? Why should the animal be well pro- 

 vided with sense organs? 



2. What is their food? Are all plants eaten or are some 

 avoided? See how the mouth parts are used in feeding. 



3. What are the important enemies of grasshoppers? How 

 do they escape their enemies? Do they hide? Are they pro- 

 tectively colored? How does jumping serve them better than 

 crawling? How many times its length can a grasshopper jump? 

 Why are wings needed? 



4. During late summer and autumn you may find individuals 

 depositing eggs. See if you can determine how the end of the 

 body is worked into the ground. 



For study it is desirable to use a rather large, freshly killed 

 or alcoholic specimen. 



The body is divided into three well-marked regions. 



1. The Head. Is it movable? Does it need to be as mova- 

 ble as your own head ? It bears several organs. 



(a) The compound eyes. Examine one with a lens or remove 

 its outer covering and examine it with a compound microscope. 

 You should understand the structure of the whole eye and how 

 it gives a single visual image. 



(b) The ocelli, three in number, one near the middle of the 

 front part of the head and the others placed near the bases of 

 the antennaa. 



(c) The antennce. Why are they so flexible? Examine one 

 with a microscope and notice the spines. What are these for? 



(d) Mouth parts. These should be studied later. 



2. The Thorax. Why should it be large and comparatively 

 firm? This portion is more or less distinctly divided into three 

 parts, each of which carries a pair of legs. 



(a) Compare the three legs of one side. Do they have the 

 same number of segments? Do all of the joints of the leg move 

 in the same plane? The five divisions of a leg are, beginning 

 with the basal end: coxa, trochanter (immovably joined to the 

 coxa in the leaping legs), femur, tibia, and tarsus, which is com- 

 posed of four movable pieces. Why do the femurs of the leap- 



