48 



NEW YORK STATE MUSEUM 



Imago. Length, 3.5-4.5 mim.; 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 mai-gins of ocelli blackish. Wings 

 hyaline, with the usual i>uri)lish streak along the radius for t\^'X) 

 thirds its length. Abdomen pale yellowish brown on base and 

 aj>ex, the middle two thirds washed with gra}; 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 nmle forceps as shown in the* accompanying 

 figures (figs.8and9). 



Fig. 8 Venation of wing- of ?Caenis allecta 

 sp. nov. 



Fig. 9 Ventral view of 

 male abdominal append- 

 ages of VCaenis al- 

 lecta sp. nov., imago. 



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

 ditional. 



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

 broken and obscure line between the paired ocelli, antennae and 

 legs pale, a pair of brown sulmiedian 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 coi)ious]y beset with short hair that is usually covered 

 with adherent silt. 



Aside from the not very satisfactory differences of coloration, 

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

 sides of the prothorax parallel; in diminuta the prothorax is 

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

 covered by the oi>or(ular lamella; in this species that lamella 



