220 THE SCOTTISH NATURALIST 



clean glass slide and lay out its appendages in the desired 

 position. 



Lay another slide on the top, protecting the specimen from 

 too much pressure by a small square of paper or card 

 laid on either side of it. The paper should be free from 

 the powdery "dressing" that .comes out of many writing 

 papers when wet. I use thickish blotting paper, in one 

 or two layers as required. 



Bind the two slides together by a pair of small elastic bands, 

 and place the whole in a jar of spirit (free of naphtha) and 

 leave overnight, or longer. 



Separate the slides. The insect, now quite rigid, will adhere 

 to one of them. Gently push it into a watch-glass of 

 absolute alcohol, or, if the specimen have delicate wings, 

 it may be safer to leave it on the slide, and simply turn 

 the latter over the watch-glass, making sure that the alcohol 

 actually bathes the entire insect. Leave a short time to 

 ensure dehydration. 



Clear in clove oil or carbol-xylol. 1 



Mount in balsam. 



In the case of larvae and adults with short appendages, 

 pressure between the slides is unnecessary. From the 

 bath of distilled water they are taken through 50 per cent, 

 alcohol, 90 per cent., to absolute alcohol. 



In thus treating insects with KOH one must try 

 to strike the happy medium between under-clearing, thus 

 leaving remnants of undissolved tissue which will produce 

 opaque blotches in the transparency, and over-treatment, 

 which may destroy characteristic markings, etc., in the 

 chitinous investment. If one has not before dealt with 

 the species under treatment, it is wise to proceed cautiously, 

 using one or two specimens experimentally if material 

 is abundant, or when the specimens are few and precious 

 taking them out of the KOH every (qw minutes (when 

 they are seen to be clearing) for examination in clean 



1 This is the formula of Cole : 



Pure xylol . . . 100 c.c. 



Absolute phenol . . 100 grammes. 



Dissolve with gentle heat, and filter. 



Modern Microscopy, 3rd edition, p. 283. 



