This month I will be introducing you to the insect pests that are the bugbear of archives, libraries and paper-based collections alike. These pests can be divided into two categories, those that eat and live in paper and those that feed on added organic materials such as animal glue, gelatin and starch.
The three main culprits are the Common booklouse, Silverfish and even the Furniture beetle commonly referred to as Woodworm. All three amigos have a voracious appetite for books be they hardbacks or paperbacks they are not fussy eaters!
The Common booklouse (Liposcelis bostrychophila)
The most common species of booklouse is Liposcelis bostrychophila and these are commonly found amongst old books in heated buildings. The adult is wingless, flesh coloured and is usually less than 1mm in length so they are virtually microscopic. The young are born as miniature versions of the adult and are known as nymphs. The total lifespan is usually no more than a few months.
The Common booklouse © Andy Murray
These little critters like to feast on microscopic moulds found growing on materials such as paper, cardboard and starch. They use their chewing mandibles to scrape up the mould which causes grazing and consequent damage to the paper.
Pest damage to one of our antiquarian books caused by the Common booklouse.
The Silverfish (Lepisma saccharina)
Our next little foe is the Silverfish which most people associate with damp bathrooms but strangely enough these little creatures also likes to settle down with, or rather, in a good book!
Adult Silverfish © Christian Fischer
These small, scaly, wingless insects are 10-15mm in length and are a silvery grey in colour with long antennae. Their abdomens taper into a tail which consists of three distinct bristles while their bodies move in a wiggling motion similar to a fish. Silverfish are nocturnal creatures that thrive in damp conditions, in fact they require humidity levels above 75 – 95% in order to breed and multiply successfully. A Silverfish infestation in a book or paper collection or indeed any museum or archive is cause for serious concern as it is a clear indication that humidity levels are far too high and such conditions will provide a perfect environment for mould growth which will in turn promote increased pest activity thus creating the perfect storm.
Silverfish feed on glue, starch, ink and microscopic moulds and although they have comparatively weak mandibles compared to the the Booklouse, they can cause just as much damage. Books destroyed by Silverfish are easily recognisable by their grazed and ragged pages which are often peppered with irregular holes.
Silverfish damage to one of our antiquarian books.
The female will deposit her eggs in small crevices laying fewer than 60 eggs at a time. These eggs will hatch into nymphs which eventually grow to adult size and will live for 5-7 years.
Furniture beetle/Woodworm (Anobium punctatum)
Our final beastie is the Furniture beetle which is a wood boring beetle that measures between 1.5-2mm in length, is winged and brown in colour.
A fully developed adult Furniture beetle about to leave its hole © Kai-Martin Knaak
Furniture beetles feed on wood which contains a high moisture content. They are particularly attracted to wooden objects in general including furniture, ply with animal glue and some composite cellulose materials. The beetles can often be found in damp books and can attack the wooden boards of books as well as the pages!
The adult will lay its eggs on or under the surface of a wooden item and the hatched larvae will bore through the object as it is feeding. Larvae will also bore through compressed paper such as the pages (also known as text block) of a thick book especially if the book is constructed using animal glue or any starchy material. The larvae will then pupate and hatch into a beetle which will exit the object through the small boreholes that they create. These adults will then go on to breed, lay more eggs in more books and so the cycle continues with newly hatched larvae causing further destruction and devastation within book and paper collections.
Larvae of a Furniture beetle © CSIRO
Damage caused by Furniture beetle.
Next month I will be discussing other internal and external factors that can cause damage to books.