THE GRASSHOPPER. 5 



THE ABDOMEN. 



1. Count the abdominal rings. 



2. Observe two grooves running along the under surface 

 of the abdomen. The under part of the abdomen, 

 included between these grooves, is the sternum, the 

 side of the abdomen is called the pleurum, and the 

 upper part is the tergum; the corresponding parts of 

 each separate ring are the sternite, pleurite, and 

 tergite. 



3. Just above the groove which separates the sternum 

 from the pleurum is a row of small holes, the breath- 

 ing pores, or spiracles; count them. 



4. In a live specimen, watch the movements of breathing. 

 All insects breathe by means of a complicated system 

 of air tubes, the tracheae, which branch from the 

 spiracles throughout the body. Can the grasshopper 

 be drowned by holding its head under water ? Connect- 

 ed with the air tubes, in grasshoppers and other strong 

 flying insects, as bees and flies, are large air sacs, which 

 fill with air, and are said to aid, like little balloons, 

 in keeping the insect in the air. By carefully cutting 

 away the roof of the abdomen, these air sacs may be 

 seen, marked by their white walls ; the white air 

 tubes, or trachea, may also be readily seen. 



5. Under the bases of the wings, on the first abdominal 

 ring, is a pair of thin, shiny, oval membranes, the 

 tympana, or ear drums. The inner surface of each 

 tympanum is connected with a nerve; but several 

 investigators have denied the auditory nature of this 

 apparatus. H 



6. The abdomen of the female ends in four points ; in 



