12 



WATERS FROM WHICH COLLECTIONS WERE MADE. 



The nymphs in the State Laboratory collections were de- 

 rived from a large variety of waters : from the broad Mississippi 

 and Ohio, slow and majestic, but flowing more hurriedly at a 

 few points — as at Rock Island and Golconda ; from the bottom- 

 land lakes of these streams, muddy and without much vegeta- 

 tion ; from the lower course of the Illinois, broad, shallow, slow- 

 flowing, with the bottoms more of mud than sand, the shores 

 often margined with water vegetation ; from the broad and 

 shallow bottom-land lakes along this river, some slightly deeper 

 than others, but abounding in floating vegetation, — as Quiver, 

 Thompson's, and Dogfish lakes near Havana, — some shallower 

 and swampy, as the great expanse of Flag Lake, and others 

 changeable and temporary in character, as Phelps Lake ; from 

 the smaller affluents of the rivers, usually flowing with an oc- 

 casional descent over ]3eds of mud, sand, and gravel ; from the 

 small lakes which rest in the ancient glacial hollows to the west 

 of Lake Michigan in Illinois and Wisconsin, quite deep in places, 

 permanent in character, usually well supplied with aquatic life 

 of all kinds ; from the shallow ponds of similar origin scattered 

 over the state, of all degrees of permanency ; and, lastly, from 

 the rapid flowing rocky streams of Yellowstone Park. These 

 waters present a great variety of situations, each with its char- 

 acteristic forms, and it is interesting to note how each of these 

 situations is occupied by a definite series of nymxDhs, in accord- 

 ance with its particular character. 



NYMPHS INHABITING THE VARIOUS SITUATIONS. 



The nymphs may be roughly grouped in three divisions, 

 according to the kind of situation preferred by them. The first 

 includes groups having the endophytic habit of oviposition, 

 Ztjyopfeni and y^scluiidw, as well as a few of the more agile 

 members of the other families, such as Hagenius among the 

 Gomphidie, and Mesotlieinis, Celithemis, and Trcuuea among the 

 LibdluUdce. The lighter-colored of these clamber among sub- 

 merged vegetation, while the dark-colored forms [Ca/opteri/g- 



