208 



COLEOPTERA 



CHAP. 



formed for swimming, the tarsi loni/cr tlian the tibiae. This family 

 is limited to the one genus Pelobius (Hygrdbia of some authors). 

 Like Amphizoa, to which it is in several respects analogous, it 

 has a singular geographical distribution ; there are only four 

 known species, one lives in Britain and the Mediterranean region, 

 one in Chinese Tibet, two in Australia. Pelobius may be briefly 

 described as a Carabid adapted to a considerable extent for 



about in water 



living in and swimming 



differing thus from 



\ 



FIG. 94. Pelobius ttirdus. Britain. A, Young larva ; B, adult larva ; C, imago. 



(A and B alter Schiodte.) 



Amphizoa, which has no special adaptation for swimming. The 

 larva of Pelobius is remarkable; it breathes by means of branchial 

 filaments on the under surface of the body, the spiracles being 

 present, though those of the abdomen are very minute and the 

 others small. The head is very large, the mandibles are not 

 tube-like, the food being taken after the manner of the Carabidae ; 

 the 8th abdominal segment ends in three long processes ; the 

 small 9th segment is retracted beneath them. The adult Pelobius 

 tarclus is remarkable for its loud stridulation. The sound is pro- 

 duced by an apparatus described correctly by Charles Darwin : J 



1 Descent of Man, i. 1890, p. 338; The views of Laudois aud Recker, Arch. f. 

 Naturgesch. Ivii. 1, 1891, p. 101, are erroneous. 



