WATEB-BUGS, WATEE-SCOEPIONS, ETC. 229 



All the GeocoriscB are terrestrial with, the exception of the 

 HydrometridcB, which are generally found upon the surface 

 of the water. 



Everyone who has been accustomed while in the country 

 to spend any time by the water's side, must have noticed 

 those curious insects which seem to have the wonderful power 

 of walking or rather progressing upon the surface of the 

 water. These creatures are commonly called Water-Measurers, 

 and often, but erroneously. Water-spiders. Not a few of 

 them are very abundant, and may be found almost every- 

 where and at any season of the year. They are gregarious, 

 wary, and active. Some of them frequent both stagnant 

 and running water, and others either the former or the 

 latter. The Sydrometra, Gerris, and Velia are the principal 

 genera of the SydrometridcB, the different species of which 

 may be treated while in confinement in almost the same 

 way. Many of them will be content with house-flies kiUed 

 and placed upon the surface of the water, and some of 

 them after a time will suck the juices from a piece of raw 

 meat suspended in the right position. As most of these 

 insects possess wings, and those which do not have them 

 are very agile climbers, the aquarium in which they are con- 

 fined should be covered. It should be also remembered that 

 they are carnivorous, and wiU be likely to feed upon each 

 other unless they are properly associated and properly fed. 



Fig. 144. Hydrohetra STAGNORUjr. 



Sydrometra stagnorum (Fig. 144) is a very remarkable- 

 looking insect, reminding one by its appearance of Euclid's 

 definition of a line, for the creature has length, but seems to 



