C^NIS 33 



The two species, Baetis pumilus and Baetis 

 niger, differ from all the other British species of 

 Baetis in having as a rule the intermediate 

 nervure of the hind wing forked, as shown in 

 Fig. 10. 



Caenis 



PLATE IV 



I have given on Plate IV a figure of Ccenis 

 halterata, one of the larger species of Canis, and 

 a fly which does not bear a popular name. A 

 curious feature about the 

 genus is the rapidity with 

 which the change from the 

 sub -imago to the imago 

 takes place. The little sub- F IG. 10. Hind wing of 

 imago will settle on one's 

 coat, dig its claws into the 

 fabric, and almost instantly the imago will 

 emerge and fly away to join its fellows, leaving 

 its cast-off clothes behind. Frequently the 

 change takes place actually in the air, and 

 imagines may be seen flying about with the 

 cast-off shucks, like bundles of old clothes, 

 hanging around them in rags and tatters. 



Of the species mentioned above, dimidiata 

 and rivulorum are extremely minute, and occur 



c 



