22 THE COCCIDAE 



spaces unfilled with balsam appear a few hours after completing 

 the mounting, put a minute drop of the balsam at the edge of the 

 cover adjacent to the unfilled spaces and allow it to run under the 

 cover. If the balsam gets thick, it can be thinned by the addition 

 of xylol, chloroform, or benzol, depending upon the solution 

 originally used to dissolve it. The solution in xylol is the one 

 most generally used. Specimens should never be mounted in the 

 natural or unthinned Canada balsam. Such balsam will never 

 harden and the preparations, where it is used, are always soft and 

 sticky. When the mounting is completed or before the slides are 

 handled much, they should be heated gently by placing them on a 

 steam radiator or over an alcohol lamp to drive off the xylol and 

 to fasten the cover-glass in place. Care must be used in heating 

 with a lamp not to allow the balsam to boil and fill the preparation 

 with bubbles. 



Specimens mounted in glycerin jelly have the advantage of 

 being more opaque than those mounted in balsam. Such prepar- 

 ations are likely, especially if stored in a warm place, to have the 

 mounting media disintegrate and the preparations become worth- 

 less for study. Such specimens can be remounted by placing the 

 slides in hot water and dissolving the glycerin jelly. They can 

 then be remounted in the glycerin jelly or dehydrated and cleared 

 and mounted in balsam. The prepared glycerin jelly can be pur- 

 chased from dealers in microscopic supplies. 



Labelling. Each slide should be carefully labelled. This 

 should be done as they are completed. The labels should be written 

 with India ink or waterproof ink. Ordinary writing fluids become 

 illegible in a few years. It is always of great advantage to marl: 

 the slide in such a way that the mounted specimens can be con- 

 nected up with the original lot of material from which they were 

 obtained. 



Rapid Method. While many entomologists depend upon the 

 external appearance of the scale in the Diaspidinae, the only abso- 

 lutely safe method of idenification is a study of the characters of 

 the body of the insect itself. Considerable time is required to make 

 a preparation for such a study. A preparation showing the pygidial 

 fringe will often serve every purpose. Glycerin jelly alone or 

 combined with glacial acetic acid, nine parts of the glycerin jelly 

 to one of the acetic acid, is used for making such preparations. 

 The acetic acid acts as a clearer and its addition is an advantage. 

 The specimens should be removed and placed on a slide with just 

 sufficient of the glycerin jelly to mount the specimens. The slide 



