l()2 AN INTRODUCTION TO EX TO.*.: 



short di-' , taking i > to slip quickly into tin 



:uft of grass or clod where the soil \ ith 



olor of their bodies." 



ut thirt 1 from the Unit. 



and British America. These all belong to the genus Sii/dt?. 



:nily XVIIL- Yi:i 1AKK.* 



The I't/iadic includes insects which are allied to the 



riders both in structure and habits. In both families, the 



.eiit of the tarsi is more or less bifid, and the claw- 

 rted before the apex. These characters distinguish tin 

 families from all other 1 leieroptera. In the Y the boil 



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- 

 td of for rowing, as with the Hydrobatu: 

 The Yeliadiu " pass most of their lives upon 

 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.) 



9 than a dozen species have been described from the United 

 but these represent six genera. 



Family XIX. HYDROBATIDyE.t 



This family includes elongated or oval insects which live upon 

 the surface of wat< very abundant on our 



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

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

 nun The head is inserted in the thorax up to the base of tin- 



are round and prominent. The antenna- arc- long, and 

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

 and its thicl the prominent middle and posterior 



liich project beyond the >ides. No scutellum is apparent 

 <-pt in Stiphania), but in its pla< id of the dorsal plat 



* Velladae: Vtlia, a proper name. 



Hylrob.i-' T t'titfs (ftarrj^), one that treads. 



