196 PAPERS BY DR. B. CLEMENS. 



The wings thus treated should be permitted to remain on 

 the glass slide after the under side has been deprived of their 

 scales, and protected from injury by a thin piece of mica, or 

 thin glass cemented to the surface by common paste or some 

 of the cements used for making microscopic preparations. 

 The slides may be an inch wide and two inches long, and 

 may contain one or more specimens. In order that they may 

 be easily distinguished, the slides should be covered with 

 paper, leaving openings through which the wings can be 

 seen, and the names of the family, genus and species written 

 upon it. 



The following is the method used by M. Guenee, which 

 the student may prefer : (< I commence by depriving the 

 wing, on both sides, of nearly all its scales, by means of the 

 solution of gum that is used to take impressions of them 

 [between two pieces of paper or tissue-paper, which are 

 moistened with the solution of gum, I suppose, and submitted 

 to light pressure] ; and as some scales are not taken off by 

 this treatment, especially those which cover the subcostal 

 vein of the fore-wings, I submit it several times to a separate 

 impression, and I finish by brushing away, with the point of 

 a pencil, all the scales that remain on it. Afterwards I place 

 the wings, still wet, between two perfectly equal slips of glass, 

 and secure them with a little wooden vice [the clothes-pin 

 which opens and closes by means of a spiral spring answers 

 a very good purpose for this use], and bind around the slips 

 a little band of black paper, which I turn over slightly on 

 each end. When ah 1 is dry I remove the compressor, and 

 obtain thus a very transparent frame, on the side of which 

 I write the name of the species, and which presents, for study, 

 the greatest convenience." 



In order to save space, the contraction " F. w." will be 

 used for Fore-wings ; and unless the fore-wings are specified, 

 the categories must always be understood to refer to the hind- 

 wings. 



The " secondary cell" is formed within the disk of the 

 fore-wings by a branch from the subcostal vein ; it will some- 

 times be contracted into " 2ndy cell." 



