THE CANADIAN ENTOMOLOGIST 359 



As I approached it, several times in succession, on each oc- 

 casion the insect squared the elbows of its fore limbs nearly at 

 right angles to the body, the femur bent close against the long 

 coxa, and the tibia pressed against the femur. This alert, de- 

 fensive attitude had a terrifying aspect which was enhanced by a 

 loud, rasping sound produced by rubbing the borders of the hind 

 femora against the rim of the fore wings. The outer free border 

 of each fore wing is thickened by a chitinous rim which is finely 

 serrate. In the region of the hind femur the border of the wing is 

 slightly emarginate, allowing free play to the thigh under ordinary • 

 circumstances. The femur itself is smooth, carrying a few minute 

 hairs, but without any rough edge. 



When the insect is alarmed, each hind femur is rubbed de- 

 liberately to and fro against the saw-like edge presented to it 

 along the concave border of the wing, and a very effective stridulat- 

 ing sound results from the friction. The same sound can be closely 

 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 Gongylus, where 

 the emargination is still more pronounced.** 



Quite recently I have become acquainted with a paper by J. 

 Wood-Mason: On the presence of a stridulating apparatus in certain 

 Mantidce, (Trans. Ent. Soc. London, 1878, pp. 263-7) in which he, 

 described the toothed edges of the tegmina of Gongylus, and sup- 

 posed erroneously that the sound, which he had never heard, 

 would be produced by the rubbing of the abdomen against the 

 toothed edge. Professor Westwood asked Wood-Mason how it 

 was that nobody had ever heard the Mantidse stridulate, these 

 insects being common enough where good observers have been. 

 The answer was "fthat the species in which the stridulating ap- 

 paratus is present are few in number;" and it may be added that 

 they only perform under the right kind of stimulation applied at 

 the right moment. 



The homing instinct which we admire so much in bees and 

 ants and wasps has been shown to depend to a surprising extent 

 upon the chemical or olfactory sensitiveness of these insects, many 



**Spolia Zeylanica, vol. Ill, p. 226, Colombo, 1906. 



