permanent slide mounts can be made. For reference collections, permanent mounts
are preferable; but for rapid survey work, temporary mounts are frequently prepared.
Berlese's medium, Hoyer's medium, and methylcellulose are examples of temporary
mounting media. Permanent mounting media include Canada balsam, euparal, clarite,
piccolyte, and permount.
4-10. TEMPORARY SLIDE MOUNTS
Thin, translucent arthropods too small to be studied without the aid of a
microscope should be mounted on slides. Such specimens include small larvae, adult
fleas, Iice, mites, bedbugs, ticks, and male genitalia of mosquitoes. The temporary slide
mount is easy and efficient. It is important that the arthropod be killed properly; most
soft-bodied, immature arthropods are killed in hot water (65 C). Larvae should never
be boiled since this procedure introduces air bubbles into the body of the larva and
destroys delicate structures necessary for identification. Most arthropods should be
kilied and preserved in alcohol untiI ready for slide mounting (but see para 4-7a for
mosquito larvae). When mounting such specimens as fleas, ticks, Iice, and mites, it is
necessary to decolor or dissolve nonchitinous tissue in order to observe internal or
obscured structures. The decoloring procedure may be accomplished by mechanical or
chemical means. Some mosquito larvae may be adequately studied without decoloring.
a. The Mechanical Procedure. This procedure can be accomplished by
puncturing the body wall of the specimen with a fine needle. The membrane punctures
should be made in the membranous areas between the segments. The body fluids and
contents are then "pumped out" by slight intermittent pressure with a brush or a small
blunt probe. Unremoved fragments are especially annoying if the specimen is to be
stained, since specimens often stain intensely. The "pumping out" process is best
accomplished in a shallow dish of water under a dissecting microscope. Care should be
taken to avoid destruction of internal taxonomic structures used in identification.
b. The Chemical Procedure. This procedure is accomplished by soaking the
specimen in a miId caustic solution. Either sodium hydroxide (NaOH) or potassium
hydroxide (KOH) (1 KOH pellet per 5 ml water) can be used in concentrations of 5 to 10
percent. Bleaching agents such as sodium hypochlorite (bleach) may also be used.
High concentrations of any clearing agent should be avoided as they wiII result in
damage to the specimen. The specimens may be left in the solution for several hours
at room temperature. Clearing may be accelerated by heating the solution. Care
should be taken to preclude specimens from becoming too pale. In any case,
observation should be clearing time wiII vary greatly from specimen to specimen. On
occasion air bubbles may get into the specimen being treated; therefore, the specimen
should be removed. This is best accomplished under a microscope in the same manner
used for "pumping out" the body contents. Unless the caustic solution is neutralized,
the tissues wiII continue to deteriorate after the specimens are mounted. Therefore,
after the specimens have been sufficiently cleared or depigmented, the next step should
be to transfer them to a small dish of distilled water that has been acidified with a drop
or two of glacial acetic acid or 15 percent hydrochloric acid.
MD0170
4-9