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 jemur-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. 
