CH. I 



AQUATIC BEETLES 



31 



is particularly easy to observe them from a low 

 bridge crossing a still stream. 



Fig. I. — Gyrinus marinus (G. natator hardly differs). Head, seen from beneath, 

 showing mouth-organs and lower pair of eyes ; antenna ; third leg ; and tarsal 

 joints of do. separate and extended. 



The Gyrinus appears quite early in the season, but 

 only in twos and threes. Those which appear in 



