396 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.37. 



Notes. — The variation in the number of cubito-anal cross- veins in the front wing 

 is in the region distal to the level of the arculus in every case but 1 wing of tseniolata 

 and 3 wings of wabashensis. 



The curving of the first cubito-anal cross-veins with the convex side distal is con- 

 stant and is most marked in the hind wing. 



In one front wing of txniolata there is a basal antenodal of the second series. 



Every specimen studied has 3 cubito-anal cross- veins in the hind wings, excepting 

 one wing of illinoiensis, which is evidently a freak. 



EXPLANATION OF PLATES. 



Plate 35. 



View looking up the Wabash River, 3 miles above Bluffton, Indiana. Six-Mile 

 Creek empties into the river just above the patch of willow herb {Epilobium augusti- 

 folium) in which man is standing. A short, narrow channel through the willow herb, 

 which grows out from the river bank on either side, is shown. This channel connects 

 two long pools, the lower of which is about 300 yards long, the upper about 150 yards. 

 These pools are closed at their lower and upper ends, respectively, with dense and 

 extensive growths of willow herb, through which the river flows in each case in a 

 narrow tortuous channel. The flow of water through the channels is, as compared 

 with the flow in the pools, relatively swift, and brooklike, and it is along the longer, 

 narrower, and swifter channels that Hetserina americana occurs in greatest abundance, 

 though it ranges over the entire river course. 



The pools are margined at the water's edge with military hibiscus, lizard tail, and 

 willows, with frequent patches of willow herb, the last extending in some cases nearly 

 to mid stream. All of these plants have become conspicuous in recent years. Willow 

 herb was formerly confined to small areas along the banks and at ripples, and fifteen 

 years ago the hibiscus was unknown here. Now it is next to the willow herb in con- 

 spicuousness along the river. These two plants, finding a congenial habitat through 

 profound changes in the river, due apparently to a lowered water level, have them- 

 selves profoundly modified and are continuing to modify the nature of the stream. 

 Lizard tail is less abundant. 



The bottom of the river where washed clean is limestone, and the depth of the pools 

 is 3 to 3^- feet. The willow herbs break the current and form frequent mud flats over 

 the river bed. 



The two pools are favorite Macromia haunts and the four species, tx-niolata, rrabash- 

 ensis, illinoiensis, and pacifira, have been taken hero, illinoiensis, however, only once. 

 The rare gomphine, Dromogomphus spoliatus, also finds these pools congenial and 

 seems to be increasing in numbers. Associated with the Macromias and Dromogom- 

 phus spoliatus as imagoes are Argia putrida, very abundant, Argia apicalis and tibialis 

 and Enallagma exsulans, less numerous, and occasionally Libellula pulchella, and still 

 more raroly Plathemis lydia."^ But the agrionines and libellulines are cosmopolitan 

 in their hal)itats and occur also at the channels with Hetserina amerieana. 



Photograph taken on July 11, 1909, about 9 a. m., cloudy, slight breeze. Newton 

 Miller and E. B. Williamson. 



Plate 3G. 



Camera placed where man stands in willow herbs in plate 35. View of the length of 

 the lower pool, looking downstream. 



a The above plants and dragonfli&s are not offered as a complete list. Only the more numerous and 

 conspicuous species are named. In this connection possibly Perithemis domitia and worn l^elated indi- 

 viduals of Gomphus graslincllus as well as the very rare Stylurus spiniceps should he mentioned. 



