1960] 
Wheeler — Ant Larvae 
91 
Covering 
It is not, however, necessary to cover a mount if it is to be studied 
at low magnifications. In fact, covering is avoided whenever possible; 
if the balsam is soft (and it may take years for the interior of a thick 
mount to harden), the weight of the cover slip will set up currents 
which are likely to move the specimen out of the desired position. 
If, however, the specimen must be studied under the high power 
objective (X440) of a microscope, a cover slip is essential. For study 
under an oil immersion objective (X970) the part of the integument 
is detached, flattened and covered. 
If a cover slip is required on a thick mount, it may be added at 
any time after the surface of the balsam is hard. A drop of xylol 
is put on the surface and a large drop of thin balsam is put on a cover 
slip. The cover slip is inverted and one edge is rested on the balsam 
mount; the opposite edge is supported by a dissecting needle while it 
is slowly lowered into position. The cover slip is then adjusted by 
needles dipped in xylol. 
If material is scarce — and especially if there is only a single larva 
— low-power studies are completed before the mount is covered. 
When material is abundant both covered and uncovered mounts are 
prepared. 
Reversibility 
It is reassuring to realize that, after the integument has been 
cleaned, every step is reversible. The same may be said of any series 
of steps and even of the entire technique from cleaned exoskeleton to 
covered slide mount. Only one precaution is necessary: hydration 
(i.e., from 95% alcohol to stain) must be gradual. 
Perfectionism 
The most important advice we can give to beginners is to avoid 
perfectionism in making mounts of ant larvae. Not only is perfection- 
ism harmful to the technician (frustration, waste of time), but it can 
be very damaging to the material. Whenever the conscientious worker 
has an almost-good-enough preparation, there is always the tempta- 
tion to try to adjust it a little bit more. Since the balsam must be a 
little thicker than usual to hold the specimen in the new position, the 
risk of damage is therefore proportionately increased and the damage 
may well be irreparable. 
It is far better to stop short of perfection in mounting and resort 
to correction of the position of the slide. Before drawing we make 
