6 OLD FLIES IN NEW DRESSES 



Fig. 4 a transverse section through the 

 fly, showing the position of the wings. 



In the Diptera (Blue-bottle, Cow-dung, 

 &c.), and PerHdse (Stone-fly, Yellow Sally, 

 &c.), the wings lie in a horizontal plane. 

 In some Diptera the wings diverge from 

 each other towards their extremities, as in 

 the Blue-bottle, shown in Figs. 5 and 6. 

 In some other Diptera and in the Per- 

 lidae, the wings lie over each other, as 

 shown in Figs. 7 and 8. It will be seen 

 that the wings in both these cases lie in 

 a horizontal plane. 



In Figs. 2, 4, 6 and 8 j3 represents the 

 section of the body, a and 7 the section 

 of the wings. 



I wish it to be thoroughly understood 

 that these positions are the positions 

 of the wings of the natural fly ivlien at 

 rest. 



Many flies when they fall on the water 

 buzz round in circles periodically, appa- 

 rently with the object of disengaging them- 

 selves from the surface. Between these 

 efforts, however, their wings generally 

 assume the normal position of rest. The 

 only way to imitate the fly when it is 



