264 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



4. A sub-oesophageal ganglion, situated in the head, 

 and sending nerves to the moutli-parts. 



5. One ganglion for each thoracic segment. In Fig. 

 139 the second and third of these ganglia lie above the 

 letters t^ and t^, and the first is nearly over the letter b. 



6. Five abdominal ganglia, one in the second, one in 

 the fomlh, one in the fifth, one in the sixth, and one in 

 the seventh segment. In the fio-ure these ffansrlia lie 

 above the letters a^, a^, a^, a^, and «^. 



7. On each side of the nerve chain, in the second and 

 third thoracic and the first to seventh abdominal segments, 

 notice the apodemata or furculce (Fig. 139, fu) projections 

 from the sterna to support the nerve chain. 



J. The auditory organs. In all the grasshoppers of 

 this family, the Acridii, the organs of hearing are situated 

 upon the sides of the first abdominal segment, and are 

 quite conspicuous externally. In order to examine them, 

 split the body of a grasshopper along the median line, 

 carefully remove all the viscera, muscles, tracheae, etc., 

 from one half, and notice the flat, oval, semi-transparent 

 tympanum upon the side of the first abdominal segment. 

 Cut it out with a pair of fine-pointed scissors ; place it on 

 a watch-glass, cover it with water, and carefully dissect 

 aAvay any tracheae which may adhere to its inner surface. 

 Examine it Avith a hand-lens or a low power of the -micro- 

 scope, and notice : — 



1. A thickened rim or bow (Fig. 140, a) which fomis 

 the margin of three sides of the organ. This rim is simply 

 a greatly thickened portion of the ordinary chitiuous 

 integument of the body. 



2. The space inside the rim is occupied by the thin, 

 semi-transparent tympanum (6), which is also a part of 

 the chitinous integument. 



