Series editors' preface - Wood Tools

296 Conservation of Furniture
can be achieved by eliminating or modifying
one or more of conditions required for growth
or poisoning wood with preservatives (see
Canadian Conservation Institute Technical
Bulletin No. 12).
Bacterial infestation is rarely found in furniture
and mostly is encountered on wet archaeological
wooden objects. Certain bacteria,
however, are able to break down cellulose,
hemicellulose and lignin under aerobic condition
but this is not a concern for furniture.
Staining from fungal and bacterial activity may
be a concern for decorative surfaces.
Insects
Insect infestation of wood may result in damage
to both structural components and decorative
surfaces. Structural damage in furniture is particularly
prevalent at joints where the presence of
animal glue provides a rich source of the nitrogen
necessary for insect development. For the
same reason woodworm are commonly found
in houses in floor boards around the lavatory.
Decoration may suffer as a result of collapse of
the surface caused by the tunnelling underneath.
When insects encounter a paint or other
opaque decorative surface layer they may tunnel
parallel to it. The result will be a diminished
substrate and potentially inadequate support for
paint, gesso or veneer.
Many different species of insects may attack
wood during its life from living tree to
seasoned timber. Insect pests are often specific
to particular types and states of wood. Some
will only attack living timber while others
require seasoned or decaying wood. Some
insects cause damage even though their use of
wood as a food source is not significant.
Insects that attack living trees and unseasoned
logs are discussed above (section 7.1.1) Those
that attack seasoned timber present the greatest
hazard to furniture. Many of the most
destructive are beetles (Coleoptera), among
which it is the larvae which do the damage,
feeding in the wood. In countries with warm
temperate or tropical climates the most destructive
pests of structural timber are termites
(Isoptera). Wood-boring weevils can accompany
wet rot. Important species of beetles
which affect furniture and interior joinery in
temperate regions include the common furniture
beetle, death watch beetle, powder post
beetle and house longhorn beetle.
Common furniture beetle (Anobium
punctatum) The common furniture beetle,
often referred to simply as woodworm, is
shown in Figure 7.6. It is the chief insect pest
of wooden furniture in the UK, Europe and
North America and is widespread in most
temperate countries, being present in many
houses, buildings and furniture. It attacks
furniture, structural timber and joinery, certain
types of plywood and wicker. Like all beetles,
Anobium has a life cycle consisting of four
successive stages: egg, larva, pupa and adult.
The adult female lays eggs, which are just
visible to the naked eye, in cracks or joints of
suitable timber, on rough sawn surfaces, in
end grain or in old flight holes. The larvae
hatch in about four weeks and bore into wood
where they may tunnel for two to five years
depending on climate and type of wood
infested, until fully grown. The refuse left
behind the larvae as they tunnel through the
wood is commonly known as frass. The
entrance tunnels are too small to be seen
without a lens. At the end of its development
period, the larva excavates a small frass-free
cavity just under the surface of the wood
before pupating and then emerging 6–8 weeks
later as the adult beetle, generally on the dark
side of the infested object, through a circular
exit hole 1.5–2 mm in diameter. A similar
pattern of complete metamorphosis is
followed by the other wood-boring beetles.
Adult furniture beetles usually emerge
between May and August, chiefly in June and
July, when they may be seen crawling on
walls, ceilings and windows, or actively in
flight. They survive for only three to four
weeks but the female can lay up to eighty
eggs, some of which are deposited on the
wood from which the adult emerged, but not
all of which will survive. Adult beetles
measure 2.5–5 mm in length and are reddish
to blackish brown. The female is generally
larger than the male. The prothorax is hood
shaped and when viewed from above almost
completely hides the head. The upper parts of
the body are covered with fine, short, yellow
hairs and rows of small pits or puncture marks
are clearly visible on the wing covers (Figure
7.6). The seasoned sapwood of most
softwoods may be attacked but some species
(including spruces and pines) are more
susceptible than others (Building Research