PREPARATION AND MOUNTING 75 



or three changes of water, so as to get rid of the 

 spirit. Having previously prepared a 10 per cent, 

 solution of caustic potash, we pour a few drops into 

 a watch-glass, or any suitable receptable (an egg- 

 cup wiU serve), and let the flea soak in it for a few 

 hours. The soaking of the object in this solution 

 must continue until the internal organs have dis- 

 solved and can be removed with gentle pressure of a 

 camel-hair brush ; but before we attempt to remove 

 them the object must have further soakings in 

 several changes of water to get rid of the potash. 

 Having cleaned the object, we now transfer it to a 

 glass slip, arrange it with a brush or needle, and put 

 slip with object on it in methylated spirit, which 

 has a hardening effect. After a few hours in spirit, 

 we transfer the object to turpentine, in which it 

 must remain until it is thoroughly permeated and 

 transparent. Then we mount in balsam in the 

 usual way. In some instances it is wise to soak the 

 object in clove oil, which clears it of spirit, before 

 transferring to turpentine. 



Larger insects require longer sacking in the 

 potash solution, and to rid them of their dissolved 

 internal organs it may be necessary to pierce the 

 skin with the point of a needle to make an exit ; and 

 after the object has been arranged on a slip, it is 

 generally best to cover it with another slip, putting 

 a piece of paper or card between the slips at either 

 end to prevent undue pressure, and tying all tightly 

 with string before placing in methylated spirit to 

 dehydrate and harden. 



Parts of insects, such as legs and wings, in some 

 cases do not need to be treated with the potash 



