Series editors' preface - Wood Tools

268 Conservation of Furniture
building. This chapter includes a brief general
review that is complemented by more specific
information on wood-boring insects in Chapter
7 and by a discussion of insect pests specific
to textiles and other upholstery materials in
Chapter 8. The steps needed to control insect
infestation are broadly the same whether
dealing with wood-boring insects or those
which normally attack textiles and are dealt
with in this chapter.
Insect life cycles All insects have a segmented
body, consisting of the head, thorax and
abdomen, six legs and an exoskeleton made
of a hard material called chitin. Insects cannot
grow continuously in the way that vertebrates
do, because of the hard exoskeleton, but
instead grow in a series of steps made possible
by moulting of the old hard skin. This
occurs in one of two quite different ways. In
incomplete or gradual metamorphosis, the
eggs hatch to resemble miniature adults
lacking only wings and the sex organs.
Periodically, they form a new soft skin under
the old hard one and when the old one is
shed the insect swells to expand the skin
which then sets hard. At the last moult the
insect acquires wings and the organs of reproduction.
Cockroaches, book lice and silverfish
develop in this way. In the alternative process
of complete metamorphosis the eggs hatch into
larvae which do not resemble the adult at all
and which normally have a completely different
lifestyle and even different diet from it.
The larvae grow by a series of moults but at
the end of the larval stage they go through a
pupation stage during which they change
completely before emerging as the adult form.
This process is used by many of the beetles
and moths. It is most frequently the larval
stage that causes damage to furniture collections,
as is the case for example with carpet
beetle and furniture beetle.
Control of insects The growth and reproduction
of insects are affected by temperature,
humidity, light, oxygen and the food source.
Insects are unable to maintain their body
temperature independently of their environment
and their metabolic processes therefore
speed up as temperature increases and slow
down as it falls. Most insect will not develop
or breed below 10 °C and will breed only
slowly between 15 and 20 °C but will breed
and develop rapidly above 25 °C. Insects
require water but their sensitivity to moisture
varies considerably. Some can obtain all they
need from food but others require relatively
high levels of moisture to sustain much activity.
Insects need oxygen but they do not have
lungs. Instead, they use a system of tubes
called tracheae which branch from openings
called spiracles on the side of the body.
Oxygen exchange occurs by diffusion and this
sets an upper limit on the size to which insects
can grow. Insects are attracted to food sources
in dark, warm, unventilated, undisturbed
environments. Food sources include wood,
textiles, upholstery stuffing, glues and storage
and display materials. Soiled or dusty materials
are most attractive. Insects can be classified
as conveniently by what they eat (and therefore
the type of damage they cause) as by their
taxonomy. The most commonly occurring
insect problems fall into three categories. The
first of these is the wood-boring insects including
furniture beetle and termites. Insects in the
second category, which includes pests such as
moth, carpet beetle and hide beetle that attack
wool fur, feathers and textiles, are important to
furniture because of the damage they cause to
upholstery covers and fillings. The third
category includes general detritus feeders,
mould feeders and scavengers such as spider
beetles, silverfish, book lice, cockroaches and
ants that generally cause a nuisance and low
levels of damage but which occasionally build
up to levels sufficient to cause serious damage.
In addition to these, problems may occasionally
be experienced by parasites such as bed
bugs (order Hemiptera, family Cimicidae) and
fleas (order Siphonaptera) that are usually a
domestic problem but which may be transferred
to institutional collections with newly
acquired objects.
Insects may arrive in various ways: via doors
and windows, through air conditioning
ducting from outside the building, from
another area within the building, through the
entry of an infested artefact, packing, storage
or display material (e.g. floral displays or
firewood), on the clothing of an employee
during the normal performance of duties in
storage areas, or on passing air flow, materials,
or personal clothing in the display area.
Insect pests may have been active in the build-