14 
and ponds, such as Flag Lake at Havana. In the smaller 
streams, where the current is often rapid, such as the Mackinaw, 
the upper Sangamon, and the Little Wabash rivers, a number 
of very interesting forms find their home, especially the 
Synthemiine, Somatochlora and other Corduliine, and the species 
related to Libellula. 
Of the third group, which live 7x the mud or sand of the 
bottom, there may be found in the streams just enumerated 
other interesting material, especially Cordulegaster, Progomphus 
and Gomphus spiniceps. In this group the most definite selec- 
tion of situations prevails. Where rapid currents flow over 
rocky beds, as in the Mississippi at Rock Island, in the Mack- 
inaw at the “ Dells,” and in the streams of Yellowstone Park, 
is the chosen home of Diastatomma (Ophiogomphus). Where 
slow currents and a muddy bottom occur, as in many prairie 
streams and ditches, Plathemis and Libellula, covered with 
dirt, trail over the mud along the shores leaving a well-marked 
track, or lie concealed amongst fallen trash, the dorsally pro- 
jecting eyes of Plathemis enabling it to remain hidden and yet 
keep a sharp lookout. The nymphs of the Cordulegasteride 
conceal themselves in the sand beneath the eddies of streams 
or under the alluvial deposit in marshes, but do not burrow. 
Hach scratches a hole for itself, and descends into it like a 
chicken into a dust bath, and, like the chicken, kicks the sand 
over its back, and does not rest until almost hidden, only the 
tops of its eyes, the tip of its treacherous labium, and the re- 
spiratory aperture at the end of its abdomen reaching the sur- 
face. The burrowers of the order are the members of the large 
and as a whole abundant genus Gomphus. These burrow shal- 
lowly along in the midst of abundant life, with the tip of the 
abdomen turned up for respiration. Some are lake or pond 
species, suchas graslinellus and pallidus. The former is com-, 
mon in prairie ponds and in the small lakes near Chicago ; the 
latter in similar localities, and in open lakes near Havana, such 
as Matanzas and Clear lakes. Others choose the larger rivers, 
being most numerous in quiet corners where fine rubbish and 
