98 



a liVht brown color. This is due to the fact that chlorine can- 

 not quite decolorize animal matter or any substance containing 

 nitrogen, as it does vegetable tissue. 



After the color has sufficiently disappeared from the wings, 

 they should be transferred to a wash composed of one part of 

 strong hydrochloric acid to ten parts of water. Here it may 

 be added, that in case the bleaching does not readily com- 

 mence upon immersion in the bleaching powder solution, the 

 action may be hastened by a previous dipping in the dilute 

 hydrochloric acid. In the bleaching solution, a crust of calcic 

 carbonate, formed by the union of the calcic hydrate of the 

 solution and the carbonic dioxide of the air, is deposited on the 

 wings, and this calcic carbonate the final wash in the dilute 

 acid will remove. As soon as the calcic carbonate has disap- 

 peared, and all bubbling, consequent upon its decomposition by 

 the hydrochloric acid, has ceased, the wings should be well 

 soaked in pure water. They may then be secured on cards 

 with a mucilage of gum tragacanth ; or upon glass, by the 

 proper transfers through alcohol and chloroform to Canada 

 balsam. 



A solution of sodic hypochlorite, known as Ean de Labar- 

 raque, or a solution of potassic hypochlorite, known as JEau de 

 JaveUe, when used in place of the solution of bleaching powder, 

 does not leave a deposit of calcic carbonate on the wings, and 

 thus dispenses with the wash of dilute acid. A solution of zinc 

 hypochlorite acts more delicately than the solution of sodic 

 hypochlorite, and may be used in place of the latter, as may 

 also solutions of aluminic hypochlorite or magnesic hypochlorite. 



These bleaching processes preserve the most delicate wings 

 unbroken, and when the specimens are of rare species, 

 "rubbed" wings can be used, the absence of the scales not 

 being evident after bleaching. The costal venation of Hespe- 

 ridae can be clearly determined in bleached wings. 



Provided the wings are not kept too long in the bleaching 

 solution, or in the dilute acid, the scales remain perfect and in 

 position, although rendered so transparent that their presence 

 is scarcely noticeable even with the aid of a lens. That they 

 still remain, is easily proved by examining the torn edge of a 



