THE INSECTS. 321 



Ronalds gives Perla bicaudata as the stone-fly, which is 

 found in June on the banks of the Thames and elsewhere. 

 " Fuscous ; head with irregular longitudinal tawny or orange 

 streak behind ; abdomen ochreous beneath ; setae nearly as 

 long as the body ; antennae as long as setae ; wings fus- 

 cescent, with darker nervures ; a tawny or orange lon- 

 gitudinal streak along the body " (Stephens). Newman 

 places it in the next genus, Isogenus, on account of the 

 sexes being similar in habit, by both possessing ample 

 wings, and calls it Isogenus nubecula, the stone-fly : dark- 

 brown ; anterior wings hyaline, slightly tinged with brown, 

 and having a little oval cloud of a darker brown on the 

 costal margin, situated about one-third of the distance 

 from the tip towards the body; posterior wings beautifully 

 hyaline iridescent ; legs pale-brown. 



Mr. Newman says that this species is abundant in the 

 neighbourhood of running water in Herefordshire, Worces- 

 tershire, Nottinghamshire, &c., and is a favourite food of 

 trout and grayling. 



The YELLOW SALLY, Perla lutea of Ronalds, is placed by 



THE YELLOW SALLY, 

 i, Perfect insect ; 2, Larva magnified. 



Mr. Newman in the genus Chloroperla Chloroperla lutea; 

 the Perla /lava of Pictet. 



The various WILLOW- FLIES belong to the genus Nemoura, 

 which Stephens divides into fifteen species ; fourteen of 

 them have a X-like plexus of nervures towards the apex 



x 



