BUTTERFLIES, MOTHS AND CICADAS 211 



of the bugs. The species common in the Hazara 

 district was Oncotympana obnubila. Farther to the 

 east in the Kangra valley was a second species of 

 very similar appearance, Platylomia brevis. It was 

 the latter species that I more carefully examined, but 

 the following account of the musical apparatus is, I 

 think, applicable to both. These cicadas are stoutly 

 built insects about two inches in length. They are of 

 a dark brown colour with a number of green markings, 

 and support on either side a pair of beautiful trans- 

 parent wings. The cicadas spend the day clinging 

 motionless to the trunks of the trees. Their colours 

 are a distinct advantage to them in this habitat, since 

 they blend so closely with the bark that the insects 

 are with difficulty seen. On sunny days they become 

 a little restless, and in the open glades may be seen to 

 take swift sallies into the air. They are widely dis- 

 tributed in altitude and may be heard at all elevations, 

 from the low-lying valleys up to a height of 10,000 

 feet. An occasional insect may be heard at any hour 

 of the day, but it is at sunset or when the sky is 

 darkened with impending rain that the woods vibrate 

 most loudly with their shrill importunate cry. 



I will pass immediately to the musical organs of the 

 cicada, and, since I have not been able to understand 

 clearly the mechanism of the instrument from the 

 descriptions that I have seen in works of natural 

 history, I will here describe in a little detail how it 

 seems to me that the music is produced. 



I must first enter on a few simple anatomical facts. 

 I will mention five structures, each of which is in 

 some way related to the production of the sound. 



A simple inspection of the under surface of a cicada 



