WATER-STRIDERS. 



texture, with small head and prominent eyes. Their 

 size is never large and their color is black, sometimes 

 marked with white or yellow. 



VELIID.E 



These have been called Broad-shouldered Water-striders 

 (see Gerrida?). Rhagovelia obesa is very common in some 

 localities, preferring swift streams. It is black, about an 

 eighth of an inch long, and usually wingless. Rhagovelia 

 plumbed lives on the Gulf of Mexico, near the shores. 

 Members of this family are more given to going into the 

 water than are their relatives and they may sometimes be 

 seen running, back downwards, on the under side of the 

 surface film. 



GERRID^E 



The family name of this group of Water-striders or 

 Pond-skaters has usually been given as Hydrobatidas. 

 Unfortunately there have been considerable changes in the 

 taxonomy of Hemiptera, as you will notice, and no agree- 

 ment has yet been reached. One system is to make the 

 Veliidae, Mesoveliidae, and Hydrometridas subfamilies 

 of Gerridas. Of Gerridas, in the narrow sense, and now 

 put in the genus Gerris, one common species (marginatus} 

 has often been listed in the genus Limnotrechus, and 

 another (remigis, Plate XXV), in Hygrotrechus. These 

 two species and their less common relatives may be seen 

 skating about on the surface of ponds or of the less rapid 

 parts of streams, often jumping up and landing again 

 without breaking the surface film. They go about on the 

 two hinder pairs of legs, pushing with the middle pair, 

 steering with the last, and holding the front pair up so as 

 to be ready to grasp their food, which consists of either 

 living or dead insects and the like. Why are they able to 

 run on the surface of water? Because their hairy legs 

 are not wetted and so, with the slight pressure of the 

 insect's little weight, they dimple but do not break the 

 surface film. A greased needle will float for the same 

 reason. Both winged and wingless adults of the same 

 species occur. Eggs are laid at or just beneath the 

 surface of the water on almost any solid object. Adults 







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