THE MICROSCOPICAL PREPARATION OF INSECTS 223 



Substitute 50 per cent, alcohol for ten to twenty minutes. 

 Change the alcohol to 70 per cent, or 75 per cent, containing 



one or two drops of acid fuchsin, and leave overnight. 

 Wash out in the same strength of alcohol. 

 Dehydrate. 

 Clear in carbol-xylol. 

 Lift each specimen on to a slide with a wide enough pipette 



and lay out the antennae and legs very gently and rapidly 



with a snipe's or woodcock's "point." 1 

 With filter paper, take up any superfluous xylol quickly. 

 Put on a cover-glass on which has been placed a drop of 



balsam. Lower the cover-glass from the posterior dorsal 



region of the insect, so as to send the wave of balsam 



downwards and forwards, thus floating out legs, ventral 



tubes, and antennas. 



Collembola, stained as above, are also very beautiful 

 mounted in euparal instead of balsam ; indeed owing to the 

 rather lower refractive index, the tubes are perhaps even 

 better shown. In this case the carbol-xylol is dispensed 

 with, and the specimens are mounted direct from absolute 

 alcohol, being laid out in this on the slide. Scale insects and 

 their larvae, treated by these methods, also make fine 

 preparations. 



I have used other stains for chitin, but have not found 

 one more generally satisfactory than acid fuchsin. 



Many small insects may be mounted in balsam without 

 previous treatment with KOH, a prolonged bath in 

 clove oil, turpentine, or carbol-xylol rendering them 

 sufficiently transparent ; amongst such are small caterpillars 

 and small imagines such as Cecidomyia. The muscular 

 system and alimentary canal, etc.,- are often well seen in 

 such preparations. Where the eyes of an insect are a 

 character of systematic value as in Pcdiculus vestimenti, 

 it is best to avoid the use of KOH, which destroys the 

 pigment. 



Chironomus larvae are acknowledged to be troublesome 



1 One great advantage of carbol-xylol is that, during operations like 

 this, it does not absorb moisture from the air so readily as other clearing 

 agents. 



69 2 B 



