1911] Pemberton — Stridulation of the Shield- Baclced Grasshopper 83 



Species of the genera Aglaothorax and Neduba have been taken 

 from a high range of hills a few miles west of Stanford University. 

 In all of the species examined no traces could be found of the elytra 

 or wings in the female, while the elytra were present in the males 

 of all the species examined, and were practically of the same 

 make-up in all the species. These short elytra in the male are 

 admirably specialized for sound production. The elytra of a 

 male specimen of a species of the genus Neduba may be taken 

 as a fair example. 



They are 5 mm. in length, and 4 mm. in width, and flat, except 

 at the posterior and outer edges, which fold down over the body 

 They are hard and brittle except at the tip, which is membranous. 

 In the central portion they are very thin and drum-like, and 

 divided diagonally by a tough chitinous piece on the under side. 

 This piece is ridged transversely very finely, forming a file about 

 3 mm. in length. Along the lateral outer edge of each elytron 

 just above the lateral end of each file, the edge is chitinized and 

 tough, forming a scraper over which the file of the opposite elytron 

 rests and may rub. One elytron covers about one half of the other. 

 As the two elytra are exactly similar in construction, either the 

 right or the left may be above and still be able to produce the sound. 

 In some individuals the right elytron would be above and in some 

 the left. This condition differs from that in most species of 

 Orthoptera which produce sounds in a similar manner, for generally 

 there is a definite unchanging position of the wing-covers. 



By moving the elytra over one another the Neduba males 

 produce shrill, high-pitched grating sounds, not continuous but 

 intermittent. The chirps average about one hundred a minute. 

 Sometimes the sound will be continued for several minutes; at 

 other times for but a few seconds only. 



EXPLANATION OF PLATE. 

 Fig. 1. Male, Neduba sp. 



2. Male, with pronotum removed showing elytra. 



3. (a) Elytron of male enlarged, showing the position of the file and the 



drum-like vibrators, 

 (b) File enlarged. 



4. Female. 



