Certain insects, such as flour beetles and carpet beetles, feed upon
dried insects, and unless precautions are taken these may entirely
destroy a collection. To guard against them, various chemical repellents
may be placed in the boxes containing specimens. Naphthalene, of which
ordinary mothballs are composed, is one of the best repellents. A few
mothballs may be put in a cloth bag pinned securely in one corner of the
box, or the heads of common pins may be inserted into naphthalene
mothballs, and the points stuck in the corners of the box, fig. 17.
Naphthalene is chiefly repellent in action; its odor keeps out pests,
but, if they are already in the specimen boxes, naphthalene will usually
not kill these pests, and some other substance must be used.
Paradichlorobenzene, called PDB, is a good fumigant to use on pests in
the collection. It should be used in a nearly airtight container, such
as a tight trunk, bin, or case, at the rate of 1 pound of PDB to 25
cubic feet of space. The boxes of specimens, with lids open or removed,
should be placed in the container, the fumigant scattered or spread on a
piece of cloth or paper above them, and the container sealed for about a
week.
[Illustration: Fig. 17.--A naphthalene mothball mounted on a common
pin. It serves as a repellent to keep away from the collection live
insects that might cause damage. To insert the pin, stick the point
in a cork, heat the head in a flame, and then push the head into a
mothball. The pin will melt its way into the naphthalene, which will
cool and harden again almost immediately.]