THE MONTHLY BULLETIN. 



CANADA BALSAM. 



293 



For microscopical study, scale insects, plant lice, thrips, mites, etc., 

 are permanently mounted on slides in Canada balsam which has been 

 dissolved in xylol. Specimens are mounted directly in the balsam 

 either alive or freshly killed, and when so done usually retain their 

 original shapes perfectly, but are not suitable for microscopic study for 

 several months. By far the most satisfactory method of mounting 

 scale insects is to first boil them in potassium hydroxide (KOH) or 

 sodium hydroxide (NaOH) ; thoroughly wash them in water; dehydrate 

 by carrying through solutions of 30 per cent, 78 per cent and 95 per 

 cent or absolute alcohol; clear in xylol, cedar oil or clove oil and mount 

 directly into balsam. 



An excellent method of mounting the others listed above is as fol- 

 lows : Kill by pouring over them boiling 95 per cent or absolute alcohol ; 

 clear in xylol cedar oil or clove oil, and mount directly into balsam. 

 Glass slides and cover glasses are necessary for such mounts. 



PRESERVING LARV.^. 



Caterpillars or the larvae of moths and butterflies are very often 

 preserved by the inflating method, which consists in removing the 

 viscera, inflating the body and drying them over an oven until rigid. 

 The original color and much of the vestiture are thus retained in almost 

 perfect condition. The caterpillar of the red humped caterpillar, shown 

 in Fig. 175, has been thus cured. 



Caterpillars and the larvae of other insects are also excellently pre- 

 served by first boiling them in water and placing them directly in a 

 permanent solution prepared as follows : 



Alcohol (1)7 per cent) 15 c.c. 



Formalin (40 per cent) 15 c.c. 



Water (distilled) 120 c.c. 



