The Stridulation of Corixa. 255 



edge is provided with a row of numerous, closely-set bristles 

 or cilia (fig. 1 ., a) while a raised keel, with another row of 

 rather stronger bristles (fig. 1., b) runs in a curve over the 

 inner face of the joint, both ends terminating at the inner 

 (lower) edge. These rows of bristles, which are found on the 

 feet of both sexes, are not, I believe, strong enough to pro- 

 duce the music which has been heard from the insects. But, in 

 the males of all the species which I have yet examined, I find 

 situated between the second row of cilia and the outer edge 

 of the foot, a row of strong, deeply set teeth (fig. 1., c). I have 

 no doubt that the shrill note of Corixa is due to the vibration 

 of this " comb, " quickly drawn across the face. A single 

 row of teeth, like that shown in fig. 1., seems to be usually 

 present in the males of Corixa. In C. striata, however, this 

 has been divided into two short rows (fig. 2.), the proximal of 

 which (c) is situated towards the middle of the inner face of 

 the foot, and the distal (d) towards the outer edge. In 

 most of the species, the teeth resemble blunt pegs, but in 

 C. striata they are sharp and conical (fig. 2, e). 



The individual Corixa which was heard by Mrs. Thompson, 

 was kindly forwarded by her, but arrived in too broken a con- 

 dition for specific determination. Its sex, however, was 

 evident, and it was a male. It seems clear, from the absence 

 of the sound-producing teeth on the feet of female Corixce, 

 that singing, in these insects, is an accomplishment reserved 

 for the males ; a similar state of things to that found in other 

 stridulating insects, such as the cicads, which were con- 

 gratulated by the ungallant poet, upon having " silent wives." 

 The "song" doubtless serves as a call-note to the female. 



Across what particular part of the face the comb is 

 drawn, will perhaps be discovered by careful observation of 

 living Corixa in the act of stridulation. The nature of the 

 rarer, twittering note heard by Mrs. Thompson, must also 

 remain doubtful for the present. She noticed that, while the 

 shrill note was accompanied by a lateral motion of the legs, 

 the twittering was due to their upward motion. I find upon 

 the femora a large number of irregularly arranged, stout 

 spines, and an upward motion of the limb would bring these 

 into contact with the edge of the face, or of the coxal 

 cavity. Vibration set up in this way, might perhaps be the 

 cause of the peculiar twittering sound. 



