THE WINGS OF INSECTS 399 



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 : — 



1 . Remove the wings carefully so as not to break the frenulum if there 

 be one;* it is well to remove the patagium first. f 



2. Dip the wings in alcohol in order to wet them. 



3. Immerse them for an instant in hydrochloric acid (muriatic acid). 

 Use for this purpose dilute acid, one part acid to nine parts water. 



4. Put them in Labaraque solution with the upper surface of the wings 

 down, and leave them there till the color has been removed from the scales. 

 If a wing bleaches slowly, the process can be hastened by dipping it in the 

 dilute acid and returning it to the Labaraque solution from time to time. 

 This solution can be procured of most druggists. It deteriorates if left 

 exposed in strong sunlight. If it cannot be obtained, use an aqueous solu- 

 tion of chloride of lime. 



5. When a wing is bleached, put it in alcohol and leave it there till 

 after it floats. This is to wash off the Labaraque solution. The wing can 

 then be mounted on a card. But it is better to mount it as described below. 



6. Transfer the wing to a clearing mixture, if it is to be mounted in 

 balsam, and leave it there five or ten minutes. This is to remove any water 

 there may be on it. A good clearing mixture can be made by mixing two 

 parts by measure of carbolic acid cr}^stals and three parts of rectified oil of 

 turpentine. 



7. Put the wing on a glass slip with considerable clearing mixture 

 under it to avoid bubbles; put Canada balsam on top, and cover with a 

 cover glass. In the case of small wings, it is best to transfer them from one 

 solution to another, and to the glass slip by means of a camel's-hair brush. J 



Wings bleached and mounted in this w^ay make an important addition to 

 a collection. The slides should be carefully laVjellcd; and the insect from 

 which the wings were taken should be kept with the slide. It is our prac- 

 tice to remove always the wings from the right side, and then to mount 

 the slide in the collection at the right of the insect from which the wings 

 were taken. Uniformity in this respect adds greatly to the appearance of 

 the collection. 



Wings of a hepialid. — Figure 416 represents the wings of a hepialid, 

 Pielus labyrinthccus, one of the most generalized members of the order 

 Lepidoptera. It is introduced here to show that there exists among living 

 Lepidoptera forms in which the venation of the wings is not greatly changed 



*i:hc frenulum is a strong spine or bunch of bristles borne by the hind wing at the 

 humeral angle in most moths. 



jThe patagia are scale-like appendages at the base of the fore wings. 



jin the case of very small wings, as those of Tineids, the very fine veins are more 

 distinct when mounted in glycerine-jelly than when mounted in Canada balsam. 



