The Life-History and Anatomy of Butterflies 



males of many species have peculiarly shaped scales arranged in 

 tufts and folds, which are called androconia, and are useful in 

 microscopically determining species (Fig. 37). The portion of the 

 wings which is nearest to the thorax at the point where they are 

 attached to the body is called the base; the middle third of the wing 

 is known as the median or discal area, the outer third as the limbal 

 area. The anterior margin of the wings is called the costal margin; 

 the outer edge is known as the external margin, the inner edge 

 as the inner margin. The shape of the wings varies very much. 

 The tip of the front wing is called the apex, and this may be 

 rounded, acute, falcate (somewhat sickle-shaped), or square. The 

 angle formed by the outer margin of the front wing with the inner 

 margin is commonly known as the outer angle. The correspond- 

 ing angle on the hind wing is known as the anal angle, and the 

 point which corresponds to the tip or apex of the front wing is 

 known as the external angle (Fig. 38). A knowledge of these 

 terms is necessary in order to understand the technical descrip- 

 tions which are given by authors. 



If a wing is examined with the naked eye, or even with a lens, 

 a clear conception of the structure of the veins can rarely be 

 formed. Therefore it is generally necessary to remove from the 

 wings the scales which cover them, or else bleach them. The 

 scales may be removed mechanically by rubbing them off. They 

 may be made transparent by the use of chemical agents. In the 

 case of specimens which are so valuable as to forbid a resort to 

 these methods, a clear knowledge of the structure of the veins 

 may be formed by simply moistening them with pure benzine or 

 chloroform, which enables the structure of the veins to be seen 

 for a few moments. The evaporation of these fluids is rapid, and 

 they produce no ill effect upon the color and texture of the wings. 

 In the case of common species, or in the case of such as are abun- 

 dantly represented in the possession of the collector, and the 

 practical destruction of one or two of which is a matter of no 

 moment, it is easy to use the first method. The wing should be 

 placed between two sheets of fine writing-paper which have been 

 moistened by the breath at the points where the wing is laid, and 

 then by lightly rubbing the finger-nail or a piece of ivory, bone, 

 or other hard substance over the upper piece of paper, a good 

 many of the scales may be removed. This process may be repeated 

 until almost all of them have been taken off. This method is 



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