228 



ZOOLOGY 



body made up of segments, having jointed appendages, three 

 pairs of legs, and breathing through a system of air tubes called 



trachece. It also belongs 

 to the order Orthoptera 

 (straight wings) because 

 the hind wings, when at 

 rest, lie folded up length- 

 wise close to the body. 



Locust (red-legged grasshopper); Ah, abdomen; Ant., 

 antennae; E, eye; M, mouth; P, pads on feet; 

 T, thorax. 



External Structure} — Any 

 common form, as Melanoplus 

 femur-rubrum , may be used. 

 Examine the body of the grass- 

 hopper. The anterior region 

 is the head, the middle part 

 the thorax, the posterior the 

 abdomen. To which region 

 are wings and legs attached? 

 Which region is the stoutest? 

 Notice that the body is covered with an exoskeleton. This is composed of 

 chitin, a substance chemically akin to that of a cow's horn. 



The grasshopper makes its home in fields of grass. Some species live in 

 vacant lots where there is considerable earth exposed. Do such grass- 

 hoppers ever have the color of their surroundings ? How might this be of 

 service to them? 



Examine the legs of a living grasshopper, with a view to finding out their 

 position when at rest. Examine the hind legs. Do you find any adapta- 

 tions present which fit the legs for jumping ? Examine the hooks and pads 

 on the last segment or tarsus. Look for other adaptations. Besides flying 

 and hopping, the grasshopper also crawls. In a resting position, it clings by 

 means of the hooks and pads on the foot or tarsus. 



Spread out the wings. Note their position. Note any differences between 

 the two pairs. Which pair would be most useful in flight? Notice the deli- 

 cate lacelike underwings, the supporting veins of which are composed of 

 tubes that carry blood and air. 



Notice the alDdomen carefully. The most anterior segment is incomplete, 

 and bears an oval structure, the tympanum, or ear drum. Count the number 

 of complete segments in the abdomen. The female grasshopper has the 

 free end of the abdomen modified for the purpose of egg laying. Note the 

 two-parted structures making up the ovipositor or egg layer. The male 

 has a more rounded abdomen. 



Observation of the abdomen of a living grasshopper shows a frequent 

 movement of the abdomen. Count the number of movements in a minute. 

 This is the breathing of the grasshopper. Along the side of the abdomen 

 in eight of the segments (in the red-legged grasshopper) are found tiny 

 openings called spiracles. A large spiracle may easily be found in the middle 

 segment of the thorax. These spiracles open into little tubes called tracheae. 

 The tracheae carry air to all parts of the body. By the movements of the 

 abdomen just noted, air is drawn into and forced out of the tracheae. 



* For laboratory directions see Hunter and Valentine, Manual, page 101. 



