BRANCH ARTHROPOD A; CLASS IN SECT A : THE INSECTS 161 



cuticle is only a thin membrane. At these places are 

 the auditory organs or ears of the locust. The thin 

 membranes are the tympana. Only the various kinds of 

 locusts and those insects closely related to them have ears 

 of this kind. Most other insects are believed to have the 

 sense of hearing situated in the antennae. 



The abdominal segments from second to eighth are ring- 

 like in form and are without appendages. There is on 

 the side of each of these segments near its front margin a 

 tiny opening or pore called a spiracle. These spiracles 

 are the breathing pores of the locust, which does not take 

 in air through its mouth or any other opening in the head. 

 There is a spiracle near each ear in the first abdominal 

 segment, and one on each side of the mesothorax near 

 the insertion of the middle legs. 



The terminal segments of the abdomen are provided 

 with certain processes which are different in male and 

 female. The female has at the tip of its abdomen two 

 pairs of strong, curved pointed pieces which compose the 

 ovipositor, or egg-laying organ. The opening of the 

 oviduct lies between the pieces. The male has a swollen 

 rounded abdominal tip, with three short inconspicuous 

 pieces on the dorsal surface. 



Make a drawing of the lateral aspect of the abdomen 

 of a female locust; also, of a male. 



For a more detailed account of the external anatomy of 

 a locust see Comstock and Kellogg's " Elements of In- 

 sect Anatomy," chap. II. 



The external structure of the grasshopper should be 

 carefully compared with that of the crayfish; pay special 

 I attention to the mouth-parts and legs. 



The teacher should point out the homologies and 

 ; modifications. 



Life-history and habits. The eggs of the locust are 

 \ laid in the autumn in the ground in bare dry places, 



