2 12 THE INTEGUMENTAL SKELETON OF THE IMAGO. 



dissolved and the specimens have been well washed, I transfer 

 them to alcohol, in which they may be preserved for years. 



Exuvia may be made from insects which have been cut 

 into two or more parts with a razor, and such are the best for 

 studying the interior, as it is difficult to cut the exuvia when 

 made without deforming them. 



If it is desirable to bleach the exuvia, this may be done by 

 boiling them for a few minutes in a five per cent, solution of 

 nitro-hydrochloric acid. 



In all cases it is necessary to use distilled water only, as the 

 fat of an insect forms insoluble soaps with the lime in hard 

 water, which adhere to the skins and entirely destroy them as 

 specimens. 



I examine the exuvia with the simple microscope in a small 

 saucer or watch-glass, and dissect them with fine scissors, 

 after fixing them on a weighted slab of wax or cork with suitable 

 pins. 



Before attempting to dissect a skeleton which has been kept 

 in alcohol, it must be transferred to alcohol and water, other- 

 wise it will be too brittle. 



The more minute parts are removed by means of the scissors 

 or a fine knife. Knives such as are used by ophthalmic 

 surgeons are convenient, but costly. 



The division of the parts can sometimes be effected by 

 tearing the syndesmoses, but it is always safer to cut them 

 through. 



The individual sclerites, or groups of sclerites, should then 

 be placed for half an hour in strong alcohol, and afterwards 

 carefully dried at the temperature of the room, and fixed with 

 coaguline upon disc-holders or bristles according to their size. 



Disc-holders are small discs of card glued to a piece of cork, 

 through which a pin can be inserted, by which the disc is 

 held in the stage forceps when under observation, and turned 

 in any direction, an essential in examining the sclerites with a 

 compound microscope. Bristles may be fixed to discs with 

 coaguline. 



Quekett, in his ' Practical Treatise on the use of the Micro- 



