68 PREPARATION AND MOUNTING 



tliod is used, the insects must not have been placed in turpentine 

 for preservation : 



" After destroying the insects in chloroform or sulphuric ether 

 (methylated being cheaper), wash them thoroughly in a wide-neck- 

 ed bottle, half-filled, with two or three waters ; the delicate ones 

 requiring great care. Then immerse them in liquid potash (or 

 Brandish's solution, which is stronger than the usual preparation), 

 and let them remain a longer or shorter time according to their 

 texture. When ready to remove, put one by one into a small 

 saucer of clear water, and with a camel-hair pencil in each hand 

 press them flat to the bottom, holding the head and thorax with 

 the left-hand brush, and apply pressure with the other from above 

 downwards, giving the brush a rolling motion, which generally 

 expels the contents of the abdomen from the thorax. A minute 

 roller of pith or cork might be used instead of the brush. In 

 larger objects, use the end of the finger to flatten them. Large 

 objects require more frequent washing, as it is desirable to remove 

 the potash thoroughly, or crystals are apt to form after mounting. 

 Having placed them on the slides with thin glass covers, tied 

 down with thread,* dry and immerse them in rectified spirits of 

 turpentine ; place the vessel under the receiver of an air-pump, and 

 keep it exhausted until the turpentine has taken the place of the 

 air-bubbles : they are then ready for the application of the balsam. 

 Larger objects may often with advantage be transferred to a clean 

 slide, as during the drying there is considerable contraction, and 

 an outline often remains beyond the margin showing this. When 

 closely corked they may remain in the spirits two or three months. 

 As you take them from the bottle wipe as much turpentine off as 

 possible before removing the thread, and when untied carefully 

 wipe again, placing the finger on one end of the cover whilst you 

 wipe the other, and vice versa. By this means you remove as 

 much turpentine from under the cover as is necessary ; then drop 

 the balsam, thinned with chloroform (see Chapter I.), upon the 

 slide, letting the fluid touch the cover, when it will be taken in 

 between the surfaces by capillary attraction ; and after pressing 



* This applies to the more delicate ones, which will not bear transferring 

 after being once spread out and dried. 



