— 88 — 



hand lens. Represent these two veins as slightly separated 

 in your drawing. 



In the description of this wing, state in what respect it is 

 more generalized than that of Rhyphus, and in what respect 

 it more specialized. 



Wing of an Asilid. — In the description of this wing note a 

 method of coalescence of veins not exhibited by Rhyphus, and 

 call attention to each case in which this method of coalescence 

 occurs in this wing. 



Wing of a Bombylliid. — In the study of this wing 

 especial attention should be paid to the branches of media and 

 cubitus. 



"Wing of an Empidid. — The most striking feature in the 

 venation of this wing is the courses of the branches of cubitus. 



Wing of a Dolichopodid. — This wing will afford the stu- 

 dent excellent training if he will work over it carefully. 



WINGS OF LKPIDOPTERA. 



As the wing of Lepidoptera are covered with scales, it is 

 difficult to determine the nature of their venation without 

 specially preparing them for this purpose. After a student 

 has become familiar with the type of venation characteristic 

 of the order, he can usually determine the nature of any 

 particular structure by putting a drop of chloroform on the 

 part of the wing to be examined ; this will render the veins 

 more distinct for a few seconds. Or the scales can be re- 

 moved from a small part of the wing with a small, artist's, 

 sable brush. But when a very careful study of the venation 

 of a wing is to be made, it should be bleached and mounted 

 on a card or on a glass slip, in order that it may be studied 

 with a compound microscope. The following is the method 

 of bleaching wings : — 



i. Remove the wings carefully so as not to break the 



