254 



The Irish Naturalist. 



fresh-water plants and animals. 1 A translation of his remarks 

 on the subject reads as follows : — 



" The front pair of legs present a peculiar shovel-like appearance. 

 Together with the beak, they act in some species (or in all ?) as a musical 

 instrument. I have heard, only always in the evening, rather loud and 

 continuous "music" from insects which I have kept. They remain 

 under water, keeping the middle legs still, and fiddle on the beak with 

 the front legs. The synchronism of the sound with the motion of the 

 legs was clearly observed." 



It will be seen that Dr. Schmidt-Schwedt records only one 

 kind of sound, evidently the shrill note heard by Mrs. Thomp- 

 son. He observed the stridulation only in the evening, while 

 Mrs. Thompson, though finding the sound then to be con- 

 tinuous, heard it also at intervals during the day. 



Being curious to know exactly what structures on the front 

 legs produce the stridulation, I have made a microscopic ex- 

 amination of these limbs in several species of Corixa. There 

 is a general tendency in aquatic insects, towards a shortening 

 and thickening of these legs, while the intermediate and hind 

 pairs remain relatively longer, the latter usually functioning 

 as oars. Most kinds of water-beetles afford good illustrations 

 of this fact. Among the water-bugs {jCryptocerata) we notice 

 that in Noto?iecta the front legs are but little modified, closely 

 resembling the middle pair. In Nepa and Ranatra these 

 limbs are adapted for seizing prey, but in Corixa and Sigara 

 we find them much shortened and thickened. All the di- 

 visions are stout, and the tarsus or foot consists of only a 

 single joint. This has the shape of an irregular " half moon " 

 (fig. i.), whose inner or concave edge is directed downwards 

 and inwards, in the ordinary position of the limb. This inner 



Fig. i. — k Fig. 2. 



Right front tibia f \ Right front tarsus of 



and tarsus of Corixa / / Corixa striata. 



Linnei. 



}>-- 



ir>; 



Die Tier und Pflanzenwelt des Susswassers. Leipzig, 1891 (vol. ii., p. 114). 



