48 NEW YORK STATE MUSEUM 



Imago. Length, 3.5-4.5 mm.; setae, about 10 mm. additional; 

 expanse of wings, 8 mm.; fore leg of male, 3.5 mm. 



General color brown, marked with purplish or slaty gray; head 

 and thorax brown, carinae and margins of ocelli blackish. Wings 

 hyaline, with the usual pui^plish streak along the radius for two 

 thirds its length. Abdomen pale yellowish brown on base and 

 apex, the middle two thirds washed with gray; some elongate 

 blackish marks on the lateral margins of the 7th to 9th seg- 

 ments; setae white; antennae, femora and forceps yellowish; 

 tibiae and tarsi, except the terminal joint, white. Venation of 

 the wing and the male forceps as shown in the accompanying 

 figures (figs. 8 and 9) . 



Fig. 9 Ventral view of 



Fig. 8 Venation of wing of ?Caenis allecta male abdominal append- 



sp. nov. ages of yOaenls al- 



lecta sp. nov., imago. 



Nymph. Length, 2.5-4 mm.; setae, 1.5 $ to 2 mm,; J* mm. ad- 

 ditional. 



Color greenish broAvn, obscure on the head, with a transverse 

 broken and obscure line between the paired ocelli, antennae and 

 legs pale, a pair of broAvn submedian dots on the prothorax; ab- 

 dominal segments pale basally and on the sutures; gill covers 

 darker beyond the basal third ; segments 8-10 darker with a mid- 

 dorsal pale line on 8 and 9. Lateral spines on segments 3-9, flat 

 and thin, best developed on the middle segments, becoming less 

 divergent posteriorly and losing their lateral fringes of spinules. 

 Setae stout at base, rapidly tapering; middle one distinctly longer 

 in female and shorter in male than the laterals, all with scanty 

 apical circlets of spinules on the segments. Legs scantily and 

 abdomen copiously beset with short hair that is usually covered 

 with adherent silt. 



Aside from the not very satisfactory differences of coloration, 

 this nymph differs from that of C. d, i m i n u t a in having the 

 sides of the prothorax parallel; in ddminuta the prothorax is 

 widened anteriorly, and in having a greater part of the abdomen 

 covered by the opercular lamella; in this species that lamella 



