AQUATIC INSECTS 



Fork-tails, Ischnura verticalis.— This is one of the com- 

 monest damselflies in the United States. The nymphs resemble 

 those of Enallagma but their gills have longer, more tapering 

 points (Fig. 170). They occur almost anywhere in weed- 

 grown water. The adults are among the earliest damselflies to 

 emerge in the spring and the last to be seen in autumn. The 

 males are green and black ; segments 8 and 9 of the abdomen 

 are blue with a black stripe on each side. They seldom fly 

 out over the open water but flit about swamps and borders 

 wherever there is vegetation. Length of nymph, one half inch. 



"Water-bugs — Hemiptera 



Form and habits. — All water-bugs have jointed sucking 

 beaks of needle-like sharpness. Some of them dive or swim 

 in the water, coming to the surface for air (PL X); others 

 prowl over submerged vegetation, a few live on the surface 

 film. These are but a few species of the great order Hemip- 

 tera most of whose members belong to the forests and fields. 

 Although these water-bugs live on the water or close to it 

 throughout their days, in almost all cases, including all of the 

 American species, they breathe air, for they have only partially 

 committed themselves to aquatic life. They never have 

 tracheal gills. The young nymphs look and act very much 

 like the adults but they have shorter wrings and there is no 

 great change in their shape after the last nymphal molt as 

 there is in mayflies and dragonflies (Fig. 183). -^ While water- 

 bugs are comparatively few in numbers of species there are 

 apt to be large numbers of individuals. It is no unusual 

 thing to be able to catch fifty or more water boatmen with 

 one sweep of the net, or to see a hundred water striders in a 

 small streamside pool. 



Water-bugs live in protected waters, thickly grown with 



plants and littered with dead vegetation, or in gently flowing 



•streams which have still pools and coves along their course 



(PI. II). There they forage in the shallow waters where 



225 



