ACKIDIUM. 185 



(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 

 composed of four movable pieces. Do the femurs of the leap- 

 ing legs differ from the femurs of the other legs? Account for 

 this. Determine how the foot is arranged to hold to objects. 

 Have you noticed a grasshopper settle its feet preparatory to 

 jumping? Examine the joint between the femur and tibia. 



(5) Examine the wings and notice their size, shape, places 

 of attachment, and general character. Do they apparently 

 have different functions to perform? Notice how the posterior 

 wings are folded so they may be covered by the anterior. Does 

 this seem to greatly reduce their strength?^ 



3. The Abdomen. — Count the number of segments. Each 

 one is covered dorsally by a tergum and ventrally by a sternum. 

 Is the abdomen more movable than the other portions? Of what 

 advantage is this condition? The posterior ends of the abdomens 

 of male and female differ. This portion of the female is modi- 

 fied to form the ovipositor, which consists of two large pairs of 

 plates that inclose a smaller pair of plates. It is between these 

 plates that the oviduct opens. What advantage Hes in the fact 

 that the larger plates possess hard tips? Along the sides of the 

 abdomen notice the stigmata,the external openings of the respira- 

 tory system. Do you find stigmata on other parts of the body? 



Draw an enlarged side view of a grasshopper, placing the ap- 

 pendages in their proper positions. 



* You should examine the posterior wing of a beetle and see how it is 

 folded. 



