AQUATIC INSECTS IN THE ADIRONDACKS 425 



Color yellowish or greenish brown, mottled with blackish brown on the 

 dorsal side in a pattern of short streaks. Legs yellowish : femora with 

 a band of brown just beyond the middle; other brownish marks beside 

 or on all the leg sutures ; tibia shorter than the tarsus without its claw. 



Setae yellow, with a whitish fringe of hairs of silky aspect; a trans- 

 verse band of brown across them just beyond the middle, and a brownish 

 shade near the tip. 



Gills present and double on segments 1-7 ; the posterior leaf with a 

 chitinous ridge on its ventral (external) margin, not reaching the apex, 

 relatively shortest on the first gill ; the posterior leaf trilobed on segment 

 I, bilobed on segments 2-6, and simple on segment 7; the smaller, 

 thinner and more delicate anterior leaf bilobed on segments i and 2, 

 simple on segments 3-7, becoming very small on the seventh segment. 



In contrast with the gills of H e p t a g e n i a , in which the anterior 

 leaf of the gill is thickened and protects the dehcate posterior one, we 

 have in Siphlurus the anterior leaf thin and dehcate, the posterior one 

 thickened. The latter, having muscles attached to it internally, thus 

 becomes a swimming organ, capable of a smart backward stroke. Each 

 acts in concert with its fellows and with the tail fin, producing a racing 

 speed for a succession of short dashes through the water. The respira- 

 tory gill leaf, being placed at the front, is out of the way of the stroke. 



Two specimens ofCallibaetis ferruginea were taken at the 

 hatchery windows during the month of August. 



Ephemerella excurcians Walsh 



1862 Ephemerella excrucians Walsh, Acad, u at. sci. Phil. Proc. p. 377 



(original description) 



1863 Epbemerella excrucians Hagen, Ent. soc. Phil. Proc. 2 : 178 (note) 

 1885 Epheme rell a excru clan s EatoD, Liun. soc. Lond. Trans. 3:130 (a 



full descriptiou) 

 1892 Ep h emer e 11a excrucians Banks, Am. ent. soc. Trans. 19:347 



(listed) 

 1871 Ephemerella invaria, in part, Eaton, Ent. soc. Lond. Trans, p. 100 



Very few imagos of this interesting species were obtained, notwith- 

 standing the nymphs were common in Little Clear creek and even in 

 the hatchery troughs during the month of July. A single pair was bred 

 July 10, transforming to imagos the following day. Specimens were 

 taken at the trap lantern and from the hatchery windows. The species 

 is known from New York, Illinois and Michigan. 



The nymph is no. 5 of Eaton's monograph.^ This being the type 

 species of the genus Ephemerella, a genus the nymphs of which 

 show considerable differences, it is the more desirable that the immature 

 stages should be made known. 



iLlnn. soc. Lond. Trans. 1885. :]:i:i3-34, pi. -40, fig. 18-20, and pi. 64, iXg. 3-7. Unknown kouus 

 "allied to Ephemerella." 



