274 BULLETIN OF THE BUREAU OF FISHERIES. 
was a small one having brownish-gray wings, light-brown body, reddish antenne, and only two caudal 
sete. 
Accompanying this is a vial of the same date containing specimens of Pentagenia 
quadripunctata, Potamanthus flaveola, and Chirotenetes siccus. The commonest form was 
the subimago of the last named. This note has been quoted in full to call the attention of 
collectors to the diversity of appearance that may be presented by the different forms of 
a single species. Males and females differ strikingly in size of eyes, in length of legs and 
of tails, and in size and color; and each sex when adult may differ strikingly from its 
own antecedent subimago stage—the first winged stage that is assumed on leaving the 
water. ‘These differences are shown side by side for Chirotenetes siccus in Plate LX XXII. 
A single entry from Mr. Stringham’s notes (August 6), the only one applying to 
Polymitarcys albus Say, is quoted subsequently under the account of that species, page 286. 
Henry E. Schradieck, while engaged in other work at the Fairport biological labora- 
tory, at my request collected from the outside of the walls of the building, as he had 
opportunity, samples of the winged mayflies that settled there and kindly sent them to 
me in alcohol. The building is some 500 feet from the river and much nearer to the fish- 
ponds of the station, and these collections include a mixture of forms from both of these 
sources. Doubtless, Betis, Callibeetis, and Cenis came from the ponds, or from slack- 
water shoals, rather than from the open river. The other river species in the order of 
their abundance were: Chirotenetes siccus, best flyer of them all, July; Hexagenia bilineaia, 
July to October; Polymitarcys albus, September 6 to 11; Pentagenia vittigera, August 25; 
and Heptagema sp., July. 
Dr. A. D. Howard’s collections of nymphs were made with a fine-meshed dredging 
net that was drawn on lines at 25-foot intervals from the bank to the 1oo-foot line and 
from there on at 100-foot intervals. It covered several square miles of stream bed, and, 
although made primarily as a mussel survey, it furnishes much more comprehensive 
data of the insect life of the river bed under flowing water than we have hitherto 
possessed. 
Dr. Howard’s data will be published elsewhere; but it may not be out of place here 
to mention some facts concerning the river mayflies as evidenced by his insect collections 
that were sent me for determination. 
In this collection of over 600 specimens, sent in vials under 102 entry numbers, 
more than 75 per cent was composed of the following eight species of insect larve, in the 
proportions indicated: 
Speci- Times Speci- Times 
mens. occurring. mens, occurring, 
Dragonflies: Mayflies; 
Gomphus plagiatus............. ryt 190 57 Hexagenia bilineata.................. 38 12 
Gomphus externus 67 37 Chirotenetes Siccus. < .ci4 0000505 .c0s 0 29 15 
Stoneflies: Polymitarcys albus.................. 13 
Acroneuria ruralis@ 8r 28 Pentagenia quadripunctata.......... 5 I 
Acroneuria abnormis 2x 12 
@ The rupinsulensis of Walsh is a synonym of this species. 
The only other specimens sent in any considerable numbers were caddisworms of 
the genus Hydropsyche, of which 49 specimens were sent under 15 separate numbers. 
