252 



To Mount Larvae 



1. Place a drop of forrnalin in a hollow 

 ground slide. The drop must be just sufficient to 

 fill the cell when the coverglaes is in position. 



By means of a pipette or spoon take up a 

 larva and, removing the excess of water, allow 

 the larva to float off into the drop of formalin. 



Place the coverglass in position, avoiding air 

 bubbles, and ring with Canada balsam, etc. 



It is important that no air bubbles are 

 included, as a white deposit forms around them. 



If too much formalin has been added, the 

 excess must be carefully removed before ringing. 

 If hollow ground slides are not available, a ring 

 of balsam may be made on the slide and allowed 

 to become somewhat hard. Fill the cavity with 

 formalin, place the larva therein, and cover care- 

 fully with a coverglass. Avoid excess of fluid' or 

 air bubbles. It is best to allow the Canada 

 balsam to be just soft enough to stick to the 

 coverglass. 



Larvae mounted in this way retain their 

 characters very well, and the clypeal and palmate 

 hairs can be examined with ease. 



2. To Mount in Balsam. — If placed in alcohol, 

 oil of cloves or xylol, and balsam in the ordinary 

 way, the shrinkage of the soft parts and even 

 of the hairs is very great. 



On no account touch the larvae with forceps, 

 and only occasionally, and with the utmost care, 

 with a needle point. ' 



Place a number of larvae in a covered watch- 

 glass containing formalin. Leave for twenty-four 

 hours at least. 



