182 Life- History of the Larch Chermes 



slide, and then transferred through Alcohol absolute and 90 per cent, to 

 Alcohol 70 per cent. If any stick to the slide or cover-glass they may be 

 gently removed with a needle, and kept in the Alcohol until time for 

 complete clearing and mounting is available. 



It is, however, not advisable, though it is quite possible, to mount 

 more than one specimen under one cover-glass. 



The moulted skins of Aphids and other insects lend themselves 

 especially to this mode of preparation, which is justified by the fact that 

 no less than five pairs of delicate glands, not previously described as 

 constant, have made themselves, and the number of their facets, ap- 

 parent upon the ventral side of the Progrediens larva of the Larch 

 Chermes, immediately after hatching from the egg. 



From measurements taken, it would seem that the expansion pro- 

 duced by the pressure on the organism during the process is just com- 

 pensated for by the contraction which takes place subsequently in 

 dehydration and in the approximation of the dorsal and ventral surfaces, 

 or of the sides, and the insects can be prepared in any position required. 

 Material which has first been preserved in alcohol cannot, of course, be 

 subjected to this process. 



The following photographs, except where indicated in one case, have 

 been taken directly from these preparations, and illustrate the stages 

 of the Colonici sistens and progrediens, and the Sexupara, on Larch 

 (Larix europaea). 



EXPLANATION OF PLATES VI AND VII. 



Cnaphalodes strohilobius, Kalt. 



Development of Colonici and Hexup.na on Larch. 



Pliotograjjlis direct from Prc])arations. x 50. 

 Fig. 1. Sistens. Stage I. Before liiljcniatioii. 

 I. After Iiibcrnation. 



