The Coccidae of South Africa. 
75 
After treating with boiling KOH the insects should be transferred to 
water containing a trace of acetic acid and through two or three changes 
of water. They are then ready for passing through the alcohols to stain, 
or, if not requiring staining, to clearing media such as oil of cloves or xylol, 
and thence into Canada balsam. 
It has been found that the majority of scale insects are improved 
for study purposes by suitable staining. In fact it is practically impossible 
to wwk with unstained material of mealy-bugs and some of the Lecaniinae. 
The chitin is so delicate and transparent that the characters cannot be 
made out, and this difficulty increases with the age of the slides. On the 
other hand, some of the larger Monophlebinae, the more highly chitinized 
Lecaniinae (e.g. Hemilecanium spp.), and Diaspinae are so dense that 
staining is quite unnecessary. 
After boiling specimens they become very soft and fold easily, and 
trouble is often experienced in transferring them from one solution to, 
another, or in getting them to lie quite flat on the slide when mounted. 
This difficulty is best overcome by using a small section lifter, which may 
be made from thin silver or platinum wire flattened and slightly up-bent 
at one ead. A wooden toothpick answers quite well on occasion. 
When mounting the cleared specimens from xylol or oil of cloves into 
Canada balsam it is advisable to transfer the insect in a small drop of the 
clearing medium to balsam which is spread on the slide to almost the 
size of the coverglass used. If a drop is placed on the slide and the insects 
transferred to this it is likely that when the coverglass is applied the speci- 
mens will be carried to the edge of the glass, or if too much balsam is 
used the specimens may be found beyond the edge of the coverglass. It 
is a good rule to use as little balsam as practicable and to have it spread 
evenly before orientating the specimens and applying the coverglass. 
The following methods of staining are recommended for the purposes 
indicated : — 
(a) For small Diaspinae and other insects in which the characters 
merely require intensification. 
Stain : Picric acid in xylol or beechwood creosote. 
Method : After treating the specimens with KOH and washing, pass 
through the alcohols, 30 per cent., 70 per cent., 90 per cent., and absolute 
into xylol or beechwood creosote which contains a little picric acid in 
solution. Leave for about 1 minute and transfer to clean xylol for a few 
minutes, then mount in the usual manner. If not washed in xylol after 
staining the picric acid is liable to crystalHze out after mounting. 
{b) For differentiation of the more chitinized parts of the exoskeleton 
of Coccidae, e.g. for easy differentiation between the antennal segments 
and their conjunctiva in the Pseudococcinae, etc., the following stains 
are recommended : — 
