VARIETIES OF DUNS. 123 



with this difference, that it perceptibly decreases in 

 size. A strange inaccuracy is credited in respect to 

 the first change of this fly. It is supposed to be the 

 female brown, but that is perfectly erroneous, as the 

 difference in sex cannot be distinguished until the 

 final stage of existence, viz., that of spinners, in which 

 they propagate their species. The spinners in this 

 case are called the Great Reds, which are numerous, 

 more or less, just in proportion as their predecessors, 

 the large Browns, have been prevalent ; as is also 

 the case with the ordinary Red Spinners of the Olive 

 duns. In May the March Brown is recognised as 

 the Turkey Brown, light and dark, in accordance 

 with the weather. This fly diminishes in size as the 

 weather grows warmer. By August the fly is still a 

 little smaller, and is known as the August Brown or 

 Dun. These are seldom numerous, the nympha being 

 generally in a state of torpor in the hot months, as it 

 is a hardy insect, and partial to rough weather. A few 

 Up-winged Browns continue to haunt the surface of 

 rivers and streams for the remainder of the season, but 

 are seldom sufficiently numerous to merit attention. 



The Iron Blue Dun ranks next in importance to the 

 Up-winged Browns. This is a distinct species, and 

 is not to be confounded with the Olive Dun, which 

 is double the size. The general prevailing colour of 

 this insect is a beautiful deep blue, except upon the 

 body, where there is a faint tinge of mauve, inter- 

 mingled with blue. (For detailed description, see 

 page 150). It makes its first appearance in April ; in 

 May, however, it is infinitely more plentiful, but has 



