GEORGIAN BAY EPHEMERIDJE 121 



SESSIONAL PAPER No. 39b 



m 



Nymph: 



Measurements: Body 9 '5 to 10 mm.; setse, 7-10 mm. 



General colom* blackish brown. Head with a dark area behind middle 

 ocellus and between lateral ones; black, scroll-like markings between the eyes. 

 Prothorax has a small light spot on each side, close to median line and near an- 

 terior margin; posterior to this and, farther from the median line is another larger 

 oval light spot. Lateral to this is an elongated light area, beyond which is the 

 light rounded lateral margin of the prothorax. Abdomen is blackish brown, with 

 light brown markings. Segments 5 or 6 to 10 have a light median longitudinal 

 stripe. On each segment is a slightly elongated incurved small light spot on each 

 side of median line toward the anterior margin of the segment; posterior to this 

 and more lateral is a larger round light area, which disappears usually on seg- 

 ments 8, 9 and 10. Ventral surface is light brown with three faint dark longitudinal 

 lines, one median and two lateral. On each side of the median line in each segment 

 is a very small, white oblique line near anterior margin and posterior to this is a 

 small, white dot. Median seta shorter, slenderer and lighter in colour than the 

 lateral ones. All fringed with hair at joints. Legs light brown. Posterior 

 margin of tibia and tarsus fringed with hairs; anterior margin of femur fringed 

 with spines, whUe anterior margin of tibia and tarsus have numerous serrated 

 teeth. Inner margin of ungues with a row of teeth for its entire length. 



Choroterpes (?) basalis Banks. 



This is a late summer form. When I was beginning to think I had exhausted 

 the collecting ground, I discovered this form in a small creek which formed the 

 outlet of a chain of small lakes and which I had not visited for a month and a half. 

 Large numbers of the nymphs were found here, July 30, clinging to stones in the 

 quiet water. The next day several images emerged. As late as September 5th 

 mature nymphs could be found. On July 31 a few nymphs were taken at Station 

 Island and imagos on August 19th. 45|'"^il^ 



This later appearance of imagos at Station Island was noted also in the case 

 of Heptagenia tripunctata. Mature nymphs of this species were taken in this creek 

 May 31 and imagos emerged June 2, whereas no imagos appeared at Station Island 

 until June 11th. This was probably due to the lower temperature of the water 

 of Georgian Bay. 



Genus Ephemerella. 



Ephemerella lutulenta Clemens.* 

 Male imago: 



Measurements: Body 8-9 mm.; wing 10 mm., setsB 12-14; fore-leg 8. 



Face dark brown; a spotted reddish gray streak down carina and 2 similar 



♦Clemens, '13, p. 335. 



