192 AN INTRODUCTION TO ENTOMOLOGY. 



short distance away, taking care also to slip quickly into the shade 

 of some projecting tuft of grass or clod where the soil- agrees with 

 the color of their bodies." 



About thirty species have been described from the United States 

 and British America. These all belong to the genus Sdlda. 



Family XVIIL— Veliadae.* 



The Veliada includes insects which are very closely allied to the 

 water-striders both in structure and habits. In both families, the 

 distal segment of the tarsi is more or less bifid, and the claws are 

 inserted before the apex. These characters distinguish these two 

 families from all other Heteroptera. In the Veliadae the body is 

 usually stout, oval, and broadest across the pro- 

 thorax, (Fig. 163). The rostrum is three-jointed, 

 and the legs are not extremely long. In fact, 

 the legs are fitted for running over the water, in- 

 stead of for rowing, as with the Hydrobatidae. 

 The Veliadae " pass most of their lives upon 

 ,Ua the surface of the water, but always near the 

 banks of the stream or pond ; but they also make 

 excursions beyond the limits of the water, and move with great free- 

 dom upon the land." (Uhler.) 



Less than a dozen species have been described from the United 

 States ; but these represent six genera. 



Family XIX. — HYDROBATID^.f 



( Waters triders.) 



This family includes elongated or oval insects which live upon 

 the surface of water. Several species are very abundant on our 

 ponds and streams. They run over the surface of the water very 

 rapidly ; and, like the Whirligig-beetles, often congregate in great 

 numbers. The head is inserted in the thorax up to the base of the 

 eyes ; these are round and prominent. The antennas are long, and 

 consist of four segments. " The thorax usually widens backwards, 

 and its thickness is increased by the prominent middle and posterior 

 coxae, which project beyond the sides. No scutellum is apparent 

 (except in Stephanid), but in its place the end of the dorsal plate of 



* Veliadae: Velia, a proper name. 



f Hydrobatidae, Hydrobates: hydor (vdoop), water; bates {fl art] i), one that treads. 



