INTRODUCTORY 5 



to have realised the fact that the wings 

 of a May-fly do not He in the same relative 

 position to the body as do those of the 

 Blue-bottle, whilst in the case of the Alder 

 there is a further marked distinction from 

 both. 



The wings, in the different families of 

 flies upon which trout and grayling feed, 

 lie when at rest in three distinct positions 

 in relation to their bodies. 



In the Ephemeridse they lie in planes 

 approaching the vertical, slightly diverging 

 from each other towards their extremities. 

 Fig. 1 gives a sketch of one of the Ephe- 

 meridse, and Fig. 2 a transverse section 

 through the line a @ of Fig. 1. These 

 drawings show the relation of the wings 

 to the body. All flies have so far been 

 treated by writers on fly-dressing as 

 though their wings were in this position. 



In the Caddis-flies (Trichoptera) and the 

 Alder-fly (Sialis lutaria) the wings lie on 

 each side of the body, meeting at their 

 upper edges in front, gradually diverging 

 towards their lower edges and posterior 

 extremities. 



Fig. 3 gives a sketch of an Alder, and 



