ACRIDIUM. 181 



ing legs differ from the femurs of the other legs? 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. 



(b) 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? 1 



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

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

 Why should the abdomen be more movable than the other por- 

 tions? The posterior ends of the abdomens of male and female 

 differ. This portion of the female is modified to form the ovi- 

 positor, which consists of two large pairs of plates that inclose 

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

 oviduct opens. Why do the larger plates possess hard tips? 

 Along the sides of the abdomen notice the stigmata, the external 

 openings of the respiratory system. Do you find stigmata on 

 other parts of the body? 



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

 dages in their proper positions. 



Mouth Parts. It has already been noticed that the mouth 

 parts serve to cut off pieces of leaves, which are then passed 

 directly into the alimentary canal. For such a purpose there 

 should be holding as well as cutting parts. 



1. Pass a needle under the labrum, which forms the upper 

 lip, and notice that it is hinged and that the end is lobed. It is 

 not supposed to be homologous with usual arthropod appendages. 

 With fine scissors remove it and place it in a watch-glass contain- 

 ing water. 



2. Immediately behind the labrum is a pair of hard, dark- 

 colored organs, the mandibles, that are used in cutting the food. 

 Their position should be carefully noted, but it will be better 



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

 is folded. 



