80 
In his notes he says it corresponds with the latter species in 
habitat, season of flight, habits of oviposition, and nymphal 
habits, but is, he observes, a rather more vigorous and active 
species. Male imagos have a habit of resting flat upon the 
bare earth of a path or sloping bank at the water’s edge and 
making short sallies forth across the water, whether for prey 
or for sport or for outlook he was unable to determine. The 
nymph may be known by its peculiar form and the obtuse 
ridge along the middle of the abdomen above. Its preference 
for still water is plainly indicated in the Biological Station 
field, as it was found only in bare mud and sand on the bottom 
of Clear Lake and Matanzas Lake. In the latter it was quite 
common in the level lake-bottom, under about six feet of 
water. In the Laboratory collections are also specimens from 
Mississippi River lakes and sloughs near Quincy, and some 
from the Saline River near Shawneetown. It did not occur in 
our collections from the Sangamon River. Hagen reports 
nymphs from Michigan, Massachusetts, South Carolina, and 
Texas. 
Dr. Forbes took an imago, just emerged, at Peoria in June, 
1878. At Matanzas Lake, near the Biological Station, fresh ex- 
uvie were noted July 6 on a log near the water, and imagos 
were taken near by. A single example was taken May 27 at 
Urbana. The season of flight at Purington Lake was consid- 
erably later than that of graslinellus, according to Mr. Need- 
ham. The first adult was seen May 28; the maximum abun- 
dance was attained July 4 and early in August the last ones 
disappeared—a period of about two months, which is about 
twice as long as that of the commoner species graslinellus. 
Although the latter imago is fairly common, that of pallidus is 
singularly rare in collections—almost unknown, in fact. It is 
recorded only from Indiana, Georgia, and Louisiana. The 
Odonata offer several remarkable instances of this kind, which 
should put us on our guard against wrong judgments of dis- 
tribution and relative abundance based on the finding of ima- 
gos alone. 
