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Major pests of libraries and archives: their habits and life histories

Silverfish and firebrats
The "bookworms"
Cockroaches
Psocids or booklice
Carpet beetles
Clothes motes
Termites
Mice
Rats
Molds and mildew

 

Many persons have recognized and written about insects injurious to books and library materials through the centuries. Aristotle, 2200 years ago, wrote: "In books also animalcules are found, some resembling the grubs found in garments, and some resembling tailless scorpions, but very small." His "tailless scorpion" was probably the book scorpion, Chelifer cancroides. In fact, as of 1922, it was estimated that over 800 references to the subject had been made in the literature, including 33 by poets (Reinicke 1922).

In 1936 Weiss and Carruthers listed 439 references in their bibliography of the literature concerning the more important insect enemies of books. Since that time, hundreds of articles have appeared on topics ranging from the use of anti-feedants (Zaitseva 1987) to protection programs for book collections (Dvoriashana 1987). Obviously interest is keen with respect to the prevention and control of biodegradation of library materials.

Damage to library and archival materials is directly caused by rodents, insects, and mold. Indirect pressures on collections may be brought about by nesting from vertebrates and birds. Damage from insects to these materials results when insects use them as a food source. Both immature and adult stages of cockroaches, silverfish, various beetles, termites, fabric pests, and booklice may cause feeding damage to library materials.

In the case of beetles, the larval stage is primarily responsible for the feeding damage. The larvae chew their way through a book, immediately inside the cover and spine, ingest the material, and leave a tunnel filled with powdered excrement (frass). Once the larvae have completed their development, they pupate and the adult beetles emerge by chewing their way out. Small round exit holes are left in the book.

In this section we will discuss the more important pests of library and archival materials. Species of insects may differ around the world, but their habits, life histories, and damage generally can be recognized and summarized regardless of minor differences in speciation.

Silverfish and firebrats

FIGURE 1. - A silverfish, Lepisma saccharine L. This species is one of the most common indoor pests of library materials. (Courtesy of Kingsolver and Pest Control in Museums)

Silverfish (Figure 1) are one of the most common pests of libraries and structures. They tend to feed on products high in carbohydrates (starch) and proteins. Such materials as paper, paper sizing, prints, glue and paste, wallpaper, and drywall are favorites of silverfish. They have also been known to feed on fabrics made from plant fibers such as linen, rayon, lisle, and cotton, particularly starched linen or cotton. They sometimes infest flour and other cereal products.

Silverfish are among the most primitive of all insects and exhibit growth without a distinct metamorphosis. They are carrot-shaped in form, long and slender, broad at the fore end, and gradually tapering to the rear. Superficially they have a fish-like appearance and hence the name silverfish, or "fishmoths." They have short legs, long antennae, and tail-like appendages at the end of their body, sometimes giving them the name "bristletails." They are wingless and generally covered with scales. Some are silver in color, whereas others are mottled dark and light. The young are similar in appearance to the adults except for size. They are long-lived insects, capable of living for several years. Unlike most insects, silverfish continue to molt and grow after reaching adulthood. They generally hide in dark areas and avoid contact with direct sunlight. Thus in inhabited spaces they are generally nocturnal in habit.

Silverfish roam widely looking for food, but once they have located a suitable source, they remain close to it. They are pests of paper, particularly paper that has a glaze upon it. They are especially fond of the sizing in paper, which may consist of starch, dextrin, casein, gum, and glue (Mallis 1982). Wallpaper and wallpaper paste are commonly eaten. Heavy attacks will loosen the wallpaper, and signs of holes may appear in the paper. Often paste, sizing, and dyes are the attracting ingredients in paper products. Some silverfish prefer onionskin and cellophane, whereas newsprint, printed or unprinted cardboard, and brown wrapping paper are not eaten. Papers of pure chemical pulp are more likely to be attacked than those consisting in part of mechanical pulp. Highly refined chemical papers are often attacked.

Of the many species of silverfish in the world, 13 are known from the United States. Some prefer cool, moist environments, others warm and moist environments. Silverfish eggs are laid singly or in twos or threes. They may be laid over several days or even weeks. The eggs of the cool, moisture-loving silverfish incubate for approximately 45 days before hatching. The young silverfish may grow to reproductive age in 3 to 4 months. Temperatures of 72 F (22 C) and above favor the development of these types of silverfish, but temperatures above 98 F (37 C) will kill the nymphal forms. Development of all stages of these types of silverfish is best at 72 to 80 F (22 to 27 C) and at a relative humidity of 75 to 97 percent. Some may live as long as 3 1/2 years under these conditions.

FIGURE 2. - The firebrat resembles a silverfish, but is found in warm, moist environments indoors. (Courtesy of Illinois Natural History Survey)

The firebrat (Figure 2) prefers much warmer temperatures: 90 to 106 F (32 to 40 C) is optimum. The name "firebrat" is applied to this insect because it commonly occurs in and around ovens, bakeries, boiler rooms, and other extremely warm areas. Firebrats and other members of this group are dark-loving insects and move rapidly when lights are turned on. Like silverfish, they prefer to hide in the security of cracks and crevices during the daytime.

Firebrats mature quickly to become adults in 1 1/2 to 4 1/2 months. Batches of eggs are laid in cracks and crevices. The incubation period under optimum conditions is 12 to 13 days. The firebrat may pass through from 45 to 60 instars (stages) in its lifetime (Sweetman 1938). Injured appendages on the insect are regenerated throughout life. It is difficult to determine the difference between a mature and an immature firebrat. Freezing temperatures will readily kill nymph al firebrats.

In temperate climates silverfish tend to migrate vertically depending on the season the year. In the hot months of summer they will migrate down into the cooler, more moist portions of the building, and in the fall and winter they will tend to migrate to attics and higher levels of the building. Drying out living spaces of a building with heat in the wintertime will help to reduce silverfish populations.

The heat also eliminates the microscopic mold that grows on plaster walls and drywall providing a food source for silverfish. In cool, moist basements, and commonly in poured concrete buildings, silverfish are a year-round problem.

It is impossible to eliminate bringing silverfish into a library. Silverfish are a very common problem in cardboard box and drywall manufacturing facilities. They lay eggs in the corrugations of cardboard boxes, one of their favorite areas for egg deposition. Although the adult silverfish may not feed directly on the cardboard, they very commonly feed on the glue that holds the cardboard box together. With every cardboard box coming into a library, a new load of silverfish and their eggs is bound to arrive. Upon hatching, depending on the conditions in which the box is stored, they may then roam widely to find a suitable food source.

The "bookworms"

In the literature the term "bookworm" has been used to describe everything from silverfish and cockroaches to the larvae or grubs of beetles. Phillippus of Thessalonica early in the first century A.D. compared satirically the grammarians of that day to bookworms, thus first voicing a comparison now used so often that instinctively one thinks of a very studious person as a "bookworm." In this discussion the term bookworm is confined to the larvae of certain species of beetles known to attack books. The grubs or larvae of certain beetles are restricted to feeding on the paste and glue of the spine and covers of bindings. Others are known to excavate the pages themselves and in fact may continue feeding from one book to the next right on the shelf.

The Cigarette Beetle. - This cosmopolitan insect feeds on drugs, leather, spices, dried vegetable matter, herbarium collections, corn husk dolls, chocolate, breakfast foods, books, and rare manuscripts. The adult beetle is cinnamon-colored, covered with golden pubescence, with its

FIGURE 3. - The cigarette beetle, Lasioderma serricorne (F.) has its head tucked down at a right angle to the axis of the body. (Courtesy of Kurtz and Harris) head tucked down at a right angle to the axis of the body (Figure 3). The larva is a small, white, hairy grub with strong mandibles (Figure 4).

FIGURE 4. - The cigarette beetle larva or grub chews tunnels or galleries packed with excrement (frass) as it develops into an adult beetle. (Courtesy of Peterson)

Eggs are deposited near the surface of the binding or on the edges of the leaves and hatch in 5 or 6 days. The young grubs penetrate the book and tunnel their way up the spine or on the inside of the cover. After becoming full grown and before transforming to pupae, the grubs make their way close to the exterior surface. A pupal chamber is then hollowed out by the grub, and here the grub transforms into a pupa. The adult beetle emerges from the pupal chamber by chewing a small hole through the exterior of the binding. Approximately 2 months are needed for a complete life cycle from egg to adult. Four or more generations a year are not unusual, particularly in the tropics.

The Drugstore Beetle. - The drugstore beetle infests books and manuscripts and is another one of the "bookworms" (Figure 5).

FIGURE 5. - The drugstore beetle, Stegobium paniceum (L.) is another example of a "bookworm" whose larva and adult damage books. (Courtesy of Kurtz and Harris)

Where the cigarette beetle larvae tend to confine their feeding activity to the spine and glue that holds the book together, drugstore beetle larvae often tunnel through the pages of the book, as well as emerge through the cover and spine. This type of infestation may be found in moist storage areas of libraries. Active infestations are a threat to books and should be dealt with quickly. Only those books showing small, round exit holes associated with powder drifting onto the books and shelving, should be treated. Small, round, dark exit holes from older books, particularly pre-nineteenth century books, that show no powder associated with the holes are not active infestations and nothing need to be done to them.

Eggs of the drugstore beetle are laid singly on books. The larval period ranges from 4 to 5 months (Figure 6).

FIGURE 6. - The larva of the drugstore beetle is a grub that tunnels into bindings, covers and books. (Courtesy of Peterson) Generally 7 months is required to complete the life cycle from egg to adult in a temperate climate. In warmer climates, 4 broods per year are possible.

The Mexican Book Beetle. - This dark brown, chunky beetle is covered with fine, silky hairs. The grub is about the same length as the adult and is cream colored with a shining head and dark mouth parts. It is usually found curled and C-shaped in its frass-encrusted tunnels. This species has been reported to damage books and leather, particularly in the tropics. Old volumes with handmade paper have been badly

damaged. Injury in more recent books with clay-filled, chemical-laden paper is generally restricted to the bindings. In some instances the larvae are cannibalistic, which may explain why few individuals are found in the books when compared to the extent of damage. Infestations generally start by adults laying eggs around the edges of the binding and the larvae first eating the binding paste, then the bindings.

The White-Marked Spider Beetle. - Linnaeus in 1776 mentions that this species is very injurious in libraries. In 1934 the white-marked spider beetle was found in combination with the drugstore beetle in a large library in the eastern part of the United States. It is a cosmopolitan species and is found in storerooms, cellars of houses, museums, and warehouses where it feeds upon vegetable and animal substances including flour, cottonseed, wool, furs, clothings, roots, and dried plants (Weiss and Carruthers 1936). The adult (Figure 7) is reddish brown and has chocolate colored hairs. In the female the wing covers are marked with two patches of white hairs. The larva is similar in appearance to the drugstore beetle larva. Its life history, activities, and damage to books is also similar. The brown spider beetle (Figure 8) has been reported from three continents and is said to prefer books bound in leather and sheepskin. Usually its galleries are found in the leather over the spine.

FIGURE 7. - The white-marked spider beetle, Ptinus fur (L.) is another member of the "bookworms" whose larvae chew galleries in books. (Courtesy of USDA)

FIGURE 8. - The brown spider beetle, Ptinus clavipes Panzer larva is a "bookworm" which may damage books. (Courtesy of Mallis)

Cockroaches

Substantial damage to library materials can be attributed to various large species of cockroaches. Fecal material, streaking, and chewing damage can happen "overnight." These problems are more prevalent in subtropical and tropical areas of the world, but damage can often be found in temperate climates. Roaches are omnivorous feeders, and in some countries parchment cannot be used for legal documents because of their fondness for this material (Mallis 1982). Certain large species regurgitate a dark-colored fluid from their mouths (altar) while feeding and around their runways and hiding places.

In addition to the direct damage to library and archival materials, one must be concerned with the suspicion of cockroaches as disease carriers. Many references can be found in the literature documenting a variety of disease organisms in and on cockroaches and their fecal material. In more recent years several studies have shown that people are allergic to cockroaches, particularly to the German and American species.

Cockroaches exhibit a gradual metamorphosis. Eggs are formed in a double row encased in an egg capsule projecting from the rear of the abdomen of the female. The egg capsule is dropped and may hatch within a day or up to 2 months later depending on the species. Nymphal cockroaches emerging from an egg capsule have no wings and crawl about seeking a food source. After developing through a series of stages (instars) the cockroach will emerge as an adult capable of reproduction.

The American Cockroach. - The American cockroach (Figure 9) tends to hide in dark shaftways, basements, and false ceilings during the daytime, emerging at night to roam the library and feed on library materials. This species, 1 1/2" long, is the largest of the structural roaches and has reddish-brown wings and light markings on the thorax. It is commonly found in warm, moist situations, such as boiler rooms, steam heat tunnels, ships, and sewer systems. This species is commonly found outdoors in subtropical and tropical areas and occasionally in temperate areas. American roaches have been found thriving under several inches of snow in smoldering refuse at an open dump in Waltham, Massachussets, when the outside air temperature was well below freezing (Mallis 1982).

FIGURE 9. - The American cockroach, Periplaneta americana (L.) is very damaging to paper products and books, particularly in warmer areas of the world. (Courtesy of Mallis)

The female of this species forms an egg capsule which will be dropped or sometimes glued to surfaces. In time, nymphal roaches will emerge from the egg capsule. These young roaches will then go through a series of molts until reaching adulthood, a developmental process that takes well over a year. The lifespan of this species of cockroach from egg to death can last well over 2 years. The habit of the female to glue her egg capsules to carefully selected surfaces increases the chance of libraries importing this species into the facility on deliveries. In the southern portion of the United States, American cockroaches commonly fly around street lights. In the north they exhibit a more gliding type of flight.

The Oriental Cockroach. - The oriental cockroach (Figure 10) is a dark brown to black cockroach. The male's wings do not reach beyond the tip of the abdomen, whereas the female is essentially wingless. Its damage to library materials is similar to that of the American cockroach except that the oriental roach does not produce pelletized excrement. This roach prefers to live in cool, moist places such as sewers, basements, air-conditioning systems, and areas associated with water pipes, piping, and floor drains. Where the American roach will be found roaming on many floors of a building, the oriental roach will generally be found on lower floors and horizontal surfaces because it lacks sticky pads on its feet and cannot climb smooth, vertical surfaces. The claws on the feet of all cockroaches, however, enable them to climb rough surfaces. Like the American roach, the oriental roach is also notably gregarious. It is commonly known as the "water bug."

FIGURE 10. - The oriental cockroach, Blatta orientalis (L.). The male is on the left and female on the right. Note the absence of developed wings in the female. (Courtesy of Mallis)

The oriental cockroach, which is less wary and more sluggish than the other species, is most disliked because of its habit of traveling in sewers and living on filth. In the warm months of the year or in tropical or subtropical areas, it may enter a structure under an exterior door or through air ducts or ventilators. Interior garbage-collection chutes and incinerators are frequently infested with this species.

The female may carry the brown egg capsule for 30 hours. The capsule consists of two rows of eight eggs each. The capsule is deposited in some warm, sheltered spot where food is readily available. At room temperature, incubation averages 60 days. It takes approximately 1 year for this cockroach to reach adulthood. As an adult, it will live up to 6 months.

The Australian Cockroach. - The Australian cockroach (Figure 11) closely resembles the American roach, but can be separated from it by its slightly smaller size and the distinct yellow margins on the thorax and light yellow streaks on the sides at the base of the wing covers. It prefers warm, moist conditions. Although this species is commonly found in more tropical regions of the world, it has been found indoors in heated buildings as far north as Canada.

FIGURE 11. - The Australian cockroach, Periplaneta australasiae (Fabr.) has bright yellow markings which set it apart from the American cockroach. (Courtesy of Mallis)

The egg capsule of this species consists of 24 eggs in two rows of 12 each. After the egg capsule is dropped it takes approximately 40 days to hatch into nymphal roaches.
The nymphs take nearly 1 year to develop to adulthood. Like other large cockroaches, they will readily feed on book covers and paper products.

The German Cockroach. - The German cockroach (Figure 12) is probably the most commonly encountered indoor roach in the world. It is frequently associated with kitchens, vending areas, food-preparation areas, and catering activities. This cockroach prefers to hide in cracks and crannies during the daytime and roam nocturnally looking for food. It is usually found near sources of moisture.

FIGURE 12. - The German cockroach, Blattella germanica (L.) is normally a pest of food handling areas and does not damage library materials. (Courtesy of Mallis)

The female carries the egg capsule until hatching time. The egg capsule, which contains up to 50 eggs, subsequently splits open along a seam, and the young roaches wiggle their way out. Sometimes young roaches hatch from the egg capsule while it is still being carried by the mother. It takes approximately 3 months to reach adulthood. Each female will produce four or five capsules in her lifetime, which may exceed 200 days.

It is quite easy for a library, particularly one with an in-house dining facility or lunch room, to become infested with German roaches. Infestations may begin with egg capsules being carried in on cartons, food stuffs, and other materials. Although this species of roach usually does not damage library and archival materials, it is an obvious nuisance and harbinger of disease organisms.

Psocids or booklice

Booklice are worldwide in distribution. They are very tiny insects measuring 1 to 2 millimeters long. Most booklice infesting books and paper products have no wings. Booklice (Figure 13) superficially resemble the lice of birds, but are not true lice. They may be commonly found scurrying about books and papers, especially in damp locations, as well as in warehouses, herbaria, and insect collections.

FIGURE 13. - The booklouse is a soft-bodied, tiny insect that feeds on microscopic mold which grows on library materials in damp situations. (Courtesy of Kingsolver and Pest Control in Museums)

Although booklice are annoying in library materials and may damage the materials by being smashed between the pages, they usually cause negligible damage. During warmer months of the year they are most numerous in damp, warm, undisturbed situations. In temperate areas of the world, when buildings are heated in the winter, booklice populations are dramatically reduced. The reduction of dampness by heat reduces the growth of fungi upon which booklice feed.

Psocids feed on microscopic molds. Any material of plant origin, such as furniture, paper, or books, when stored in a damp locality, is likely to support a profuse growth of these mildews, which in turn encourage infestation by psocids (Mallis 1982). They are fond of starch, starchy pastes, and glue of books and wallpaper. Sometimes people refer to these small insects as "paper fleas." Unlike true fleas, booklice do not bite humans. They are readily introduced into a building in furniture, boxes, books, and paper, all of which may have microscopic molds upon which they feed. They hide in dark areas, behind molding and baseboards, between floors and in the wall space, and behind electrical and plumbing fixtures, as well as in many of the pipe wrappings.

The most common booklouse reproduces parthenogenetically, that is, without having to have a mate. In fact, no males have been found for some of the booklice. The nymphal booklice, upon hatching from the eggs are very tiny and do not move about much. As they molt and grow, they take on a slightly grayer appearance. The life cycle averages 110 days and may be terminated by cold weather. In an environment of continuously low relative humidity, (below 35 percent) booklice will desiccate and die.

Carpet beetles

Carpet and hide beetles (Figure 14) belong to the family Dermestidae. The hide beetles are a special pest of hides, leather, meat, and similar animal products. They are often referred to as skin beetles, larder beetles, tallow beetles, or dermestids. Rarely are hide beetles found in library materials. The larder beetle has been recorded as occurring in great numbers among books, doing considerable damage to the covers (O'Conor 1898). One would expect, from the normal feeding habits of this beetle, that leather bindings would be particularly subject to attack.

Carpet beetles are much smaller than hide beetles and are common pests of products containing protein such as woolens, rugs, carpets, upholstered furniture, museum specimens, and similar materials. Most adult carpet beetles feed largely on pollen and nectar. The larvae are responsible for damage to certain library materials. Such beetles as the black carpet beetle, the common carpet beetle, the warehouse beetle, the furniture carpet beetle, the varied carpet beetle, and the larger cabinet beetle are most commonly found in museums, libraries, and collections.

Various protein sources provide food for the larvae of carpet beetles. They are commonly found feeding on felt used for the lining of rare book containers and exhibits; felt hats and accessories; all manner of woolen goods; tapestries; embroidery; needlepoint; feathers, including those in birds' nests; rugs; objects made of horn; whale baleen; quills; wasp, yellow jacket, and hornet nests; dead insects; rodent carcasses; hair and fur; soft leather and buckskin; silk; leather book bindings; stuffed animals and birds; snake skins; horsehair stuffed furniture; brushes; woolen shoeshine buffs; feather dusters; and wool felt insulation. One carpet beetle, the odd beetle, has been found destroying valuable prints in the National Gallery, Ottawa, Canada (MacNay 1950).

FIGURE 14. Various adult and larval for carpet beetles which may be encountered in and around structures housing library materials.

A. The Black Carpet Beetle, Attagenus megatoma (F.),
B. The Odd Beetle, Thylodrias contractus Motschulsky,
C. A Carpet Beetle, Reesa vespula (Milliron),
D. The Cabinet Beetle, Trogoderma inclusum LeConte,
E. The varied Carpet Beetle, Antrenus verbasci (L.),
F. The Common Carpet Beetle, Antrenus Scrophulariae (L.),
G. The Furniture Carpet Beetle, Antrenus flavipes LeConte. (Illustrations A through D plus G, courtesy of Kingsolver and Pest Control in Museums. Illustrations E and F, courtesy of Mallis.)

The larvae are small with obvious segmentation and many hairs and bristles. The larva of the black carpet beetle is elongate and carrot-shaped and generally orange in color. The rest of the carpet beetles are shorter and generally dark in color. Most carpet beetle larvae prefer to feed in dark areas, such as at the base of the nap of a thick rug or beneath furniture. They leave behind many larval skins as they molt from one stage to the next over a period of 4 to 5 months. The larvae pupate in their last larval skin and emerge as adults to live for approximately 1 month. After egg laying, the female generally dies within a few days.

Clothes motes

The larvae of clothes moths may be destructive in a library where they feed on items high in protein. They are particularly fond of animal carcasses, furs, feathers, hair, wool, dead insects, taxidermy mounts, feather-filled upholstery and cushions, tapestries, carpets, felt, and sometimes bookbindings.

Four species of clothes moths are important in museums, libraries and collections. They are the webbing clothes moth, the casemaking clothes moth, the tapestry or carpet moth, and the brown house moth (Figure 15).

FIGURE 15. - Various fabric pest moths which have been known to infest library materials. The larvae of these moths feed on materials high in protein.

A. Casemaking clothes moth, Tinea pellionella (L.).
B. Tapestry or carpet moth, Trichophaga tapetzella (L.).
C. Webbing clothes moth, Tineola bisselliella (Hum.). (Courtesy of Mallis)

The Webbing Clothes Moth. - The most common of the four species of clothes moths is the webbing clothes moth, which is worldwide in distribution. Its name is derived from the habit of the larvae of spinning silkened tubes and runways as they feed on an item. In addition, the pelletized frass is generally stuck together in clumps by silken webbing produced by the larvae. The larva, which is a whitish caterpillar with a brown head capsule, commonly feeds in dark, protected areas.

Adult moths of the webbing clothes moth are good fliers, but tend to fly in darkened rooms and areas. The males are primarily on the wing, whereas females generally walk. The adults have been known to fly up to 300 feet, entering structures, particularly attics. Female moths lay between 40 and 50 eggs. Egg deposition occurs in darkened areas or at night. After the eggs are laid the female dies. Upon hatching, the larvae commence feeding as soon as a suitable food is available. The newly born larvae can enter any opening greater than 0.01 millimeter, which enables them to enter all manner of storage containers. Upon reaching maturity, the larva spins a pupal case of silk and transforms into an adult moth. The time from egg to egg varies from 5 to 9 months or may exceed 2 years if the larva is triggered to go into a dormant period.

The Casemaking Clothes Moth. - This moth is not nearly so common as the webbing clothes moth, but has been found in bird and rodent carcasses, Persian rugs, and wall hangings and tapestries from Central and South America, The moth has a brownish hue with indistinct dark spots on the wings. The name casemaking clothes moth is derived from the habit of the larva to spin a case of silk which is interwoven with fibers of the article on which it is feeding. When the larva moves, this case is carried around with it, and the larva will die if separated from its case. The larva does not produce silken tunnels when feeding as does the webbing clothes moth.

The life history is somewhat similar to that of the webbing clothes moth. When the larva is mature and ready to pupate, it often leaves the product on which it is feeding and attaches its silken cocoon to objects some distance from the infested product. By attaching its cocoon in such a manner, infestations are commonly transported from one place to another.

The Carpet or Tapestry Moth. - This moth is much rarer than the previous two species and is distinctly marked, so it is easily distinguished from the other two moths. The larva makes no case; instead it fashions a silken tube or burrows through the material. This tube, combined with the feeding, causes much damage to infested material.

The adults are found flying from April to June and mate almost immediately after emergence. The female deposits from 60 to 100 eggs. The larval stage persists through the summer months. A rough cocoon is constructed by the larva for pupation. One or two generations may be produced per year.

The Brown House Moth. - The brown house moth feeds on animal and vegetable matter in many countries around the world. The larval stage feeds principally upon upholstery, carpets, furs, skins, dried specimens of animals, in birds' nests, dried plants, dried fruits, and sometimes on books. In some instances this moth has been found damaging leather bindings.

The life history of this moth is extremely variable, primarily due to variations in temperature. The incubation period varies from 8 to 110 days; the larval stage from 71 to 145 days. The larva may enter a desiccation-resistant stage prior to pupation, which may last for months. The complete life cycle in the field usually takes from 11 to 13 months.

This moth has been noted as a serious pest of books with cloth bindings (Chrystal 1932). The injury was most severe to books on shelves nearest the floor and became less pronounced and disappeared entirely as the distance from the floor became greater. The feeding of the larvae showed as regular patches of varying depths on the binding with the same type of damage to the insides of the covers. The shelves contained massive amounts of excrement and traces of silken threads. Cocoons were found on shelving, in tunnels on the outer bindings, and between the covers and fly leaves.

Termites

Many kinds of termites can be found throughout the world (Figure 16). They include drywood, dampwood, furniture or powder post, subterranean, Formosan, and desert termites, to name but a few. Termites live in colonies, are social insects, and divide their work among specialized members. The members of these colonies move in passageways that are hidden from the sun's rays and are protected from undue moisture loss (Mallis 1982). Some need moist wood to survive, some nest in the ground and move back and forth between the wood source and the colony, and others can live totally within structural members or books without attachment to the ground or a water source.

FIGURE 16. - Supplementary queen (left): worker (center); and soldier (right) of the eastern subterranean termite. (Courtesy of Mallis)

Worker termites bite off small fragments of wood a piece at a time and digest the wood fragments by utilizing a diverse array of amoebae, bacteria, spirochaetes, and fungi. The worker termites then regurgitate this digested material and feed the remainder of the colony.

Cellulosic materials make up the majority of a termite's diet. Since library materials are primarily composed of cellulose, the collections constitute a banquet for termites. Not only will the termite colony attack the structural members of the building itself, but they will consume all manner of paper products. They can be particularly destructive in storage areas where inspection of the collections is minimal.

Subterranean Termites. - Worldwide, subterranean termites are responsible for millions of dollars of damage to structures and materials annually. These ground-dwelling termites nest in soil or in wood or vegetable matter in contact with the ground. They are able to reach wood or cellulosic material above ground level by means of earthen shelter tubes which the workers construct and through which they travel. They almost always have a ground connection to the colony. Rare exceptions are known where they have been able to maintain themselves in damp wood in wet areas without ground contact. The workers cement together earth and triturated wood with saliva and liquid feces to form a mudlike cement. This tubing activity is characteristic of subterranean termites and is an aid in the identification of their damage.

The workers are the only caste in the social system that can eat cellulosic materials and digest them. They in turn regurgitate digested material to feed nymphal workers, soldiers, kings and queens, secondary reproductives, and the winged forms (elates). If a section of the colony is somehow cut off from the main colony, secondary reproductives will take over the function of egg laying in this separated colony. Control measures are aimed at placing chemical barriers in the soil between the colony and the food source.

Drywood Termites. - Unlike subterranean termites, which need a source of moisture and contact with the ground, drywood termites can colonize individual portions of structural elements, furniture, or stacks of cellulosic materials. These termites are restricted to the warmer parts of the world where multiple colonies can exist in a single building. Whereas subterranean termites tend to feed in the spring wood and with the grain, drywood termites hollow out wood from surface to surface.

A distinctive sign of drywood termites is the pelletized frass generated by the workers (Figure 17). These pellets are often dumped out of the workings into a neat, conical pile through a small hole or holes which exit the galleries. A variety of control measures can be used for control of drywood termites, including chemical fumigation of structures.

Mice

The most common rodent found in libraries is the house mouse (Figure 18). This species seems to be able to invade practically any structure man has made. Damage to library materials comes from mice destroying materials for nesting purposes and urinating and defecating on library materials. Populations of mice can build up very quickly. When they die, their carcasses act as a source of food for carpet beetles and perhaps clothes moths. In addition to damaging collections directly, mice may chew the insulation off electrical wires, causing them to short and start a fire. Various diseases and ectoparasites are associated with mice and their nests.

FIGURE 18. - The house mouse, Mus musculus Linnaeus. (Courtesy of Mallis)

House mice are secretive and are generally active at night. They live in a territory with a small home range. The average distance that a mouse travels in its activities is a rough circle of 30 feet. Male mice are highly territorial, and for this reason control measures must be designed for specific areas where mouse droppings are found. They live outdoors year-round but will invade buildings, particularly in the fall of the year in temperate climates.

Mice are sexually mature in 35 days. The average litter size is about six. A female can have a litter approximately every 50 days. Community nests of mice are not uncommon, wherein several females may share the nest with their accumulated brood. They breed throughout the year indoors. Mice living outdoors are seasonal breeders, peaking in the spring and the fall.

Mice feed on a variety of foods provided by man. They also feed on dead insects found indoors. Mice have been found to be cannibalistic. They apparently do not need free water to drink, but will consume it if it is available. Mice feeding on high protein diets must supplement their diets with free liquid. During their nocturnal activity mice leave fecal droppings wherever they have been active. Other signs of mouse infestations are gnaw marks; small, stained holes in floors and walls; and a pungent odor from their urine.

Rats

A variety of rats worldwide may invade structures seeking out food and shelter. The most common rat encountered in urban situations is the Norway rat (Figure 19). Rats are important with respect to library collections because of their habit of gnawing on papers, books, and like materials for nesting material. They also can create damage to the structure itself by gnawing holes in structural timbers, doors, windows, and other building elements to gain access to food, water, and nesting sites.

FIGURE 19. - The Norway rat, Rattus norvegicus (Erxleben). (Courtesy of Ware)

The diseases of rats are well documented. Such diseases are plague, murine typhus fever, infectious jaundice, rat-bite fever, trichinosis, and others.

The female Norway rat often digs a burrow system in soft earth in which to raise her young. In most cases the burrow is located on the exterior of a building in a protected location. Occasionally this activity will enable rats to burrow into crawl spaces of buildings. In some instances rats will be found in the sewer system and may enter buildings through piping. Since rats are good climbers, they will occasionally enter buildings above ground level.

The Norway rat is a moisture-loving creature and of necessity must live near an available supply of water. It is omnivorous, but shows a preference for grain, potatoes, fruit, and eggs. Rat droppings will take on the color of the diet consumed over the previous 3 days.

Rats are capable of breeding every month of the year. The average number in a litter of Norway rats is usually six to eight. The female has an average of three to six litters per year. The young are born helpless, pink, blind, and naked. In 12 to 14 days they open their eyes and are ready to leave the nest in about a month.


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