5G M:\V YOUK STATK .MI'SKCM 



middle on both basal and apical segments, but best defined 

 apical ly. 



Bred at Ithaca Isth July. I'.mi. 



Heptagenia sp. no. :: 



The nymph of this species was nut bred. Like the two 

 preceding it is strongly marked and easily nvogni/ed. It 

 occurs in the larger streams, clinging to rueks in the swiftest 

 currents. 



The nymph, i Pl.r>. liu. l.i Length, in mm.; antenna. l\ mm., 

 and setae l.'i mm. additional. 



Body rather elongate, scarcely wider across the head than 

 across the mesothorax. Head strongly depressed, evenly rounded 

 in front, with flaring infero lateral margins, dilated at the sides 

 and distinctly visible untside the e\es. Antennae slender. pale. 

 Prothurax slightly narrowed pusteriurly. its margins flaring, 

 dilated. Legs moderate, pale; femora with indistinct median 

 and apical darker bands, and with a scanty development of the 

 usual posterior fringes of hair. \\ings reaching the level of the 

 base of the 4th abdominal segment. 



Abdomen regularly tapering posteriorly. Segments 8-10 slightly 

 diminishing in length. Id a little produced on the dorsal side, and 

 produced in a sharp triangular spine on each lateral margin; 

 lateral spines developed only on segments 7 -!l. Ix-st developed on S. 



Gills represented on segments 1-7. on 1-fi double, consisting of 

 an anterior protecting lamella and a posterior respiratory 

 lamella whose border is cut into a long fringe of branching gill 

 filaments; upper lamella obliquely oval, produced at the tip into 

 an acute spine-like point, becoming broader distally (obovate) on 

 4 and 5, and narrower again on (>. On segment 7 there is a 

 simple linear hairy filament, obtuse at the apex and hardly reach- 

 ing the level of the base of the lateral spine on the 8th segment. 



Setae 3, long and hairy, the hairs becoming whorled and finally 

 obsolete toward the tip. 



The distinctive features of the color pattern are shown in the 

 photographs reproduced in pl.9, fig.4. These are a broad 

 pale middorsal band divided with brown on the posterior 

 abdominal segments, lateral pale dashes at the sides of the 

 abdominal segments, and a brown longitudinal dash either side 

 of segments 8 and 9 below. 



