180 Life- History of the Larch Chermes 



treated, and perhaps even more so, if it is found that the Sexuparae 

 confine their oviposition only to the lower branches. 



The principal economic investigation therefore still lies before us in 

 a detailed study of the habits and structure of the Sexuales, and a 

 determination of the presence or absence of the Gallicola non-miyrans 

 generation in this country. 



Should the latter exist, it probably does so to a very limited degree, 

 and the main control upon the Sexual phase would, in this event, be 

 little disturbed. 



V. A METHOD OF PREPARING APHIDAE FOR MICROSCOPIC 

 EXAMINATION. 



While investigating the life-history of the Larch Chermes in 1913, it 

 was noticed that ordinary SvJphuric Ether had a peculiar effect in 

 "fixing'" the chitinous covering of the young stages of this insect, and 

 so of preventing crinkling and distortion. 



Later a use was found for this process in the preparation of more 

 advanced stages, both winged and wingless, and in jnounting Aphids of 

 considerable size, in addition to insects of other Orders, having extremely 

 delicate chitinous membranes. 



Finally, for detailed examination, it was found possible, even with 

 Aphids of considerable bulk, to subject the insects to pressure during 

 Ether-fixation, the resulting balsam preparations showing a minimum 

 of distortion, and presenting objects especially suitable for micro- 

 photography. 



Borner's method for preparing specimens of the Chermesidae in 

 1908 comprised a preliminary immersion in 70 per cent. Alcohol, and 

 dehydration through 90 per cent, and Absolute Alcohol. The fats were 

 then dissolved out in Sulphuric Ether, and the objects hydra ted through 

 Absolute, 90, 70, 50 and 30 per cent. Alcohols, with a final immersion 

 in Distilled water. After clearing in weak Potash, and another immersion 

 in Distilled water. Glycerine was added, and the skins finally mounted 

 in a I Clycerine solution. 



Roughly this process takes the following time: 



