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 l^e 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- 

 uvia8 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 graslineUus, 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 (jraslineJlns. 

 Although the latter imago is fairly common, that of paUidus is 

 singularly rare in collections — almost unknown, in fact. It is 

 recorded only from Indiana, Cleorgia, and Louisiana. The 

 OdoHdfa 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. 



