Cockroaches, Locusts, Grasshoppers, and Crickets 135 



that I have heard is made by a species of Trimerotropis, abundant in 

 the beautiful little glacial "parks" of the Colorado Rockies. Locusts 

 undoubtedly make sounds to be heard by each other, and it is not difficult 

 to find in them a matter of more difficulty in most other insects certain 

 organs which are almost certainly auditory organs, or ears. On the outer 

 faces of the upper part of the first abdominal segment is a pair of sub- 



FIG. 167. The red-legged locust, Melanoplus femur-rubrum, female. 

 (After Lugger; natural size indicated by line.) 



circular clear window-like spots (Figs. 165 and 55). These are thin places 

 in the body- wall serving as tympana; on the inner face of each is a small 

 vesicle, and from it a tiny nerve runs to a small auditory ganglion (nerve- 

 center) at one side of the tympanum. From this auditory ganglion a nerve 

 runs to the large ventral ganglion in the third thoracic segment. Similar 

 auditory organs are found in the other singing Orthoptera, the crickets and 

 katydids, but situated in the front legs instead of on the back. 



