This month I am responding to a query recently posted on the
Collectors Universe U.S. Coins Forum. The collector wrote:
“I got into my safe today for the first time in quite a while. To
my surprise, there were a bunch of tiny bugs crawling around in there.
The safe is a solid seal, no way that they were climbing in or out so
they must have been breeding in there. They are extremely small,
clearish brown and they look like aphids. They seem to be concentrated
the most around my Dansco albums. The safe currently houses the Dansco
albums, personal papers and a pack of silica gel. ... I am thinking of
putting them into the freezer for a day or two. Has anyone seen this before?”
A fellow participant on the forum suggested that the bugs might be
book lice. This, given his description, is a good guess. In later
postings, the collector posted images of the insects he found (one
illustrated). As I am not an entomologist, I asked my colleagues at
Insects Limited Incorporated (www.insectslimited.com/index)
to confirm my identification. The insects are, indeed, book lice.
Book lice are psocids, a member of the insect order Psocoptera.
They are small and pale to transparent in color. The presence of
psocids indicates a humid environment. Psocids are omnivores, but
research has shown that they are particularly fond of mold. Book lice
do not eat books or paper; they feed on the often microscopic mold
that can grow on paper.
The best way to control and eliminate psocids is to create an
inhospitable environment for them. Mold grows at a relative humidity
(RH) of 70 percent or higher. Keeping the RH at 50 percent or lower
will eliminate the mold growth that attracts the psocids. As the
collector had a sachet of silica gel in the safe, he may have been
trying to keep the RH down for the sake of his coin collection. The
silica gel is likely no longer conditioned to maintain a lower RH.
Determining the RH level that the sachet is now conditioned to is
fairly straightforward, providing the collector has the right
equipment. Seal the sachet in a plastic bag along with a recently
recalibrated hygrometer. Wait an hour or so and take a reading without
opening the bag.
Freezing the Dansco albums and the papers in the safe will kill
the bugs. It will not, however, kill any mold growing on these items.
To freeze, place the items in plastic freezer bags and seal
tightly. Freeze these items to a temperature of at least -4 F (-20 C)
for one week. This will kill all stages of the insect (i.e., eggs,
larvae and adults). After one week, remove the bags from the freezer
and allow them to come back to room temperature before opening the
bag. Any condensation that forms should form on the outside of the
bag. In the meantime, the collector should thoroughly vacuum the
interior of the safe to remove any insects, eggs or larvae left behind.
Alternatively, the collector could purchase new albums and discard
the infested ones. If he takes this approach, I would still recommend
that he freeze the remaining papers from the safe and clean it
thoroughly. After the freezing treatment is completed it is
recommended that the items be examined under magnification to ensure
that no bugs are left on them. Removing any bugs killed by the
treatment will prevent false alarms in the future.
Susan L. Maltby, Toronto, is a private conservation consultant,
with an interest in numismatic preservation.