190 ELEMENTARY LESSONS ON INSECTS 



do it at the first trial. The specimens, whether whole minute 

 insects, or minute parts of larger insects, are first soaked 

 in strong alcohol until the water is extracted from them. 

 Two changes of 95% alcohol may be required for this, with a 

 stay of some 5 to 10 minutes (longer if impervious) in each. 



Fig. 68. — Diagram illustrating a method of making slide mounts. Specimens are prepared on 

 the stage of a dissecting microscope, A ; then soaked in strong alcohol in the watch glass, B; then 

 cleared in carbol-turpentine in the second glass, C; then placed at x on the glass slide, D, on which 

 there has been placed a drop of Canada balsam from the bottle E. Then the coverglass is added 

 and a gummed label attached. 



Then they are transferred to carbol-turpentine or carbol- 

 xylol.* This is a clearing agent. It replaces the alcohol and 

 prepares for balsam. Then they are transferred from the 

 clearer with a forceps to a drop of Canada balsam that is 

 first placed on a slide. In the balsam they are then arranged 

 in proper position, and a thin cover glass is lowered over 

 them. When the balsam has spread out evenly to the 

 margins of the cover glass, filling the space underneath 

 completely, the mount is finished, f It should then be 



* A mixture of 1 part of carbolic acid (pure phenol crystals) to 3 parts 

 of either turpentine or xylol. 



f Small air bubbles, if accidentally included, will escape of themselves 

 slowly. More balsam, if needed to fill the space, may be added at the edge 

 of the cover; The specimens should be placed well within the margin of 



