COLLECTING AND PRESERVING INSECTS BANKS. 



67 



MOUNTING SPECIMENS ON SLIDES. 



Many insects are so minute that they can not be pinned, and can 

 only be studied by the aid of a microscope. These insects are pre- 

 served by mounting them in Canada balsam upon a piece of glass 

 called a slide (fig. 112). These slides, 3 inches long and 1 inch wide, 

 the Canada balsam in small tubes, and the cover glasses to place 

 over the insects can be purchased from all dealers in microscope 

 supplies. A drop of the Canada balsam is put on the center of the 

 slide and the insect put in, its legs or wings arranged with pins, 

 and then the cover glass put on and pressed slightly so that the 

 balsam will spread out and fill all the space. Care should be taken 

 not to use too much balsam, for the amount should be no thicker 

 than the thickness of the mounted insect, else one can not use the 

 higher powers of the 

 microscope. Sometimes 

 it is useful to heat the 

 balsam after the cover 

 glass has been put on. 

 This is done by means 

 of a small alcohol lamp, 

 purchasable from the 

 dealers. This heating in- 

 duces the balsam to 

 harden more quickly, but 

 with many soft insects 

 too much heating will 

 break the skin or drive 

 out the juices and dis- 

 color the mount. 



There are other media 

 than Canada balsam in which to mount specimens, and if any of 

 these are used it is necessary to cover the edge of the cover glass 

 with some material such as Brunswick black to prevent evaporation. 

 It is not necessary to seal up balsam mounts. Insects for mounting 

 are prepared in different ways. Sometimes it is better to kill them 

 in hot w T ater or in acetic acid. If the specimen has been in alcohol 

 this should be removed by a bit of blotting paper, and the specimens 

 placed in clove oil or xylol for a few minutes, heated slightly, and 

 then mounted in the balsam. Different methods will be found to 

 apply to different insects or their parts. After the mount lias been 

 prepared the slide should be labeled by attaching a, square gummed 

 label to one end of the slide. The slides should then be Left flat until 

 the balsam is dry, and afterwards may be arranged in a box or tray 

 (fig. 113). Wooden boxes are commonly used, each having space for 

 88552— Bull. 67—09 6 





Fig. 112.— a balsam slide mount and jacket cover for same. 



