18 EPHEMERID/E OF OTHER RIVERS. 



of British Neuroptera, and for that reason only it is worthy 

 of passing mention. It is about the size of an ordinary Blue- 

 winged Olive. The female spinner is described as follws by 

 Eaton : Wings : very shiny and clear, tinted with brown. 

 Neuration : brown amber. Thorax and Abdomen : pitch 

 brown, darker in the last three segments. The abdomen is 

 the same colour on the lower side as above. The specimen 

 here described was caught in the Schwartz wald. No records 

 are available either of the duns or male spinner. 



It must always be borne in mind that the colour of natural 

 flies varies slightly in individuals, and is always affected by 

 age. Duns, as their time approaches for the final change, 

 sometimes show the colour of the spinner very clearly through 

 the envelope. Spinners often become much darker as they 

 grow older; for example, the male imago of the May-fly turns 

 almost black in the course of three or four days, so much so 

 that it is familiarly known as the Black Drake, while the female 

 is commonly called the Grey Drake. 



A complete list of British Ephemerida3 is appended, together 

 with a short note upon each fly which should be of assistance 

 to the beginner. At the very least he will have a complete 

 record of the possibilities before him, and by a process of 

 exclusion he should be able to reduce the probabilities to very 

 small proportions. For instance, a medium-sized dun with 

 three seta? must belong either to the genus Ephemerella or 

 Lep tophi ebia, unless it is yellow, in which case it can only be 

 Potomanthus luteus. Again, a small fly with three setse can 

 only be Habrophlebia fusca or one of the genus Ccenis. Count 

 the wings and the matter is settled. Similarly, a large fly with 

 three setse must be a May-fly. 



In the case of the two-prong ers, a small fly is certain to be 

 a Pale Watery, an Olive or an Iron Blue, unless it has only two 

 wings, in which case it will certainly belong to the genus 

 Cloeon. A medium-sized fly will probably be either 

 Rhithrogena or a Little Yellow May dun; they are not 



