NOTES. 227 



When the insect is alarmed euch hind femur ia deliberately 

 rabbed to and fro against the saw-like edge presented to it along 

 the concave border of the wings and a very effective stridulat- 

 ing sound results from the friction. The sound can be approxi- 

 mately reproduced upon the dead insect by gently passing a 

 porcupine quill backwards and forwards along the wing-border. 



The serrate border of the wing is also present in the female 

 where the concavity is more pronounced ; and it seems likely that 

 the sound can also be emitted, on occasion, by the female. 



Many pther insects, especially beetles, produce sounds by rasp- 

 ing. The stridulation of the caterpillar of the Death's Head Moth 

 has been alluded to on page 47 of this volume. Many grass- 

 hoppers emit a loud clicking sound when rising from the ground 

 in flight, but I have not yet succeeded in ascertaining how this is 

 produced. The vocal apparatus of male locusts and cicadas be- 

 longs to a different category of sound-producing organs, and the 

 object of the call is also different. 



What may perhaps lend particular interest to the habit of 

 stridulation as manifested in Gongylus is the delibei'ation with 

 which the action is performed by an insect which is well known 

 in other ways for its defensive and offensive tactics. 



A. WILLEY. 

 Colombo. Januarv. 1906. 



9. Terrestrial Coluhridm of Ceylon. — In his admirable syste- 

 matic work on the Reptiles of British India, Ceylon, and Burma 

 (1890), Mr. G. A. Boulenger notes the existence of a general desire 

 felt by those not well acquainted with snakes to know at least how 

 they may distinguish poisonous from harmless kinds. It is not 

 a simple matter and there is no way of rendering it simple. The 

 examination of the teeth is the fundamental test, but they are 

 often broken and some snakes, the Dipsadinae, possess grooved 

 fangs and yet are not poisonous. It is in fact necessary to know 

 the snake before pronouncing upon its charac+er. 



In an island like Great Britain where only three species 

 of snakes occur, one of which — the adder — is poisonous though not 

 deadly, their identification is not a matter of daily or frequent 

 necessity. In Ceylon, which covers an area of some 20,331 square 

 miles, smaller in extent than that of Ireland and yet possesses an 

 ophidian fauna comprising, exclusive of the sea-snakes, upwards 

 of fifty species, of which eight are poisonous and three or four 



2 H 10-06 



