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Recognition of damage caused by pests in libraries, archives, and their collections
Silverfish
The
"bookworms"
Cockroaches
Psocids
or booklice
Carpet
beetles
Clothes
moths
Termites
Mice
Rats
The starting point for any Integrated Pest Management Program is a thorough inspection of the facility and collections to determine the status of past, current, or potential pest problems. The most difficult part of such an inspection, once damage or signs of infestation have been found, is to determine if the situation is current and active or if it is a previous infestation and therefore inactive. Holes and galleries in books will not disappear once an infestation ceases. Only a trained eye can determine if activity exists and control or prevention measures are warranted.
Damage to paper products from silverfish is caused by their direct feeding on the materials. The feeding of silverfish results in irregular feeding areas that exhibit characteristic "thin spots" (Figure 21). Silverfish do not have strong chewing mouth parts and therefore tend to sit on the surface of the paper and gradually abrade the surface. In some areas of the damage, the feeding will result in irregular holes in the paper. In other areas, however, the feeding will not break entirely through the paper and will result in thin spots or simply the removal of the printed word (Figure 22).
When silverfish feed on printed materials, they often leave a fine, pelletized frass (excrement) which is black and resembles a miniature mouse dropping. Under magnification, this residue is fairly easily distinguished as individual pellets or droppings. This material accumulates under items or may be scattered randomly over surfaces in darkened areas. It may also be found on the interior of acid-free storage boxes. Large amounts of frass may be found in attics insulated with cellulose insulation (ground up newsprint).
Feeding damage from bookworms is primarily caused by the grub-like larvae. Eggs are usually laid at the edges of the cover or on the spine, and the newly hatched larvae begin to chew their way and tunnel up the spine, in between the cover and flyleaf, or immediately beneath the cover. These frass-packed galleries meander undetected until the book is opened. The galleries will begin with a small diameter and increase in size as the larva molts to larger and larger sizes.
A flashlight inspection of the shelving can easily find indications of bookworm feeding activity. As the larvae continue to feed and as the adults chew their way out upon emergence, powdered frass falls in a pile on the shelving. This frass will be the color of the cover of the book. It can be found as piles immediately adjacent to the base of the book on the shelf or as piles on the top of the book at the edge of the cover as it stands on the shelf. These piles of frass connote an active infestation (Figure 23).
Small, round holes in the spine, cover, or pages of a book, left as larval galleries or adult exit holes, will remain for the life of the book, even though the "infestation" may not be active (Figures 24, 25 and 26). If no frass piles are found on or adjacent to the book, the infestation is not active and therefore no remedial action need be taken. Often unnecessary fumigation is performed on books exhibiting old evidence of bookworms that have long since died out.
Bookworms require an environment with high moisture content, and often infestations die out naturally when infested books are moved to drier locations.
The feeding damage of cockroaches to books is primarily done by the large species, such as the American, Australian, and the oriental roach. The American roach is probably responsible for most of the feeding damage on book covers and paper products. Large roaches have strong, chewing mandibles and bite off bits of cover and paper.
The feeding damage of large roaches is ragged in appearance and often begins at the edges of magazines and paper products (Figure 27). With repeated bites, large, excavated, ragged holes and depressions will result. The feeding on book covers resembles mold at a distance, but when viewed close-up, it is easy to see a puckered effect on the cover as individual bites have been taken out of the cover by the roaches. Large, irregular patches of feeding damage occur on covers and spines. Cockroach feeding will often remove the surface layer and begin to break into the fibers of the cloth cover (Figure 28). With leather covers, the feeding may commence all the way to the backing.
American roaches leave other signs and evidence while feeding on books and paper products. They regurgitate a brown liquid called attar while feeding and resting on materials.
This attar, which contains chemical pheromones that act as an attractant to other cockroaches, is called an aggregation pheromone. Often smears and tear-shaped droplets of this brown liquid will be left behind (on books and library materials.
American roaches may leave behind pelletized excrement on or around the products on which they are feeding (Figure 29).
The pellets are very distinctive in shape and will be the color of the material on which the roaches are feeding. Most of the time the pellets are dark in color (Figure 30). They are approximately 1/8" in length with blunt ends and longitudinal striations. These striations or ridges easily separate this dropping from a typical mouse dropping (Figure 31). Even though they are similar in size, the mouse dropping is generally smooth and has a tapered point.
FIGURE 31. - A comparison of house mouse and American cockroach droppings. American cockroach droppings are uniform, blunt-ended with longitudinal ridges, whereas house mouse droppings are irregular and tapered with no ridges.
Often American roach droppings are mistaken for mouse droppings and inappropriate pest control measures are taken. By misidentifying the droppings, baiting for mice will only aggravate the roach situation. Large cockroaches will readily feed on rodent baits without being affected by the toxins of the bait.
As previously discussed, booklice do not directly feed on paper products. They feed on microscopic molds which grow on paper products when they are stored in damp situations. By removing the paper products from these moist environments, the mold conditions will cease and the booklice will be eliminated.
Feeding of carpet beetle larvae results in characteristic frass drifting from the infested piece. The frass is a uniform powder made up of tiny granules. This powdered excrement or frass will be the color of the product on which the larvae are feeding. If they are feeding on dead insects, the powdered frass will generally be gray or tan. Feeding on a colored material will result in frass of the same color.
Another indication of carpet beetle feeding is the existence of cast larval skins. These hollow shells are left behind as the larvae molt from one stage to the next. Live, active carpet beetle larvae move quickly when exposed to light or may "play possum. when disturbed. The feeding is a series of neat, small, irregular holes in the item.
Infestations of moths are characterized by webbing, cocoons, or cases, with copious amounts of pelletized frass stuck together with the webbing. The infested material appears to be festooned with clumps of frass, webbing, and cocoons (Figure 32). Often the webbing and cocoons will extend some distance away from the infested product. On occasion larvae can be seen leaving the infested piece and moving to quiet, dark areas to spin a cocoon and emerge as an adult moth. Dead moths may also be found in the webbing associated with the infestation.
Subterranean termites construct earthen shelter tubes from the soil up into bookcases, books, or boxes of materials stored in basements. The key to identification of subterranean termite infestations is the presence of worker termites in the galleries and the presence of copious amounts of dirt (Figure 33). These grains of earth are cemented into hollow shelter tubes which act as humidity controlled highways for the termites while they feed on cellulosic materials. Once a book containing an infestation of subterranean termites has been removed from the shelf and the highway to the colony has been broken, the workers and soldiers that are trapped in the book will eventually desiccate and die. Once this attachment to the subterranean colony has been broken, thus cutting off the workers from the remainder of the colony and their moisture source, no further need for control is required for the infested item. The structure itself, however, should be treated for subterranean termites by a professional pest control company.
Drywood termites need no attachment to a colony in the ground and therefore can infest stacks of books or paper products as a distinct colony. Drywood termite damage is distinct for two reasons:
1. The workers excrete a pelletized frass the color of the material on which they are feeding. These piles of pellets appear under magnification to resemble a partially deflated football (Figure 17). All pellets in the pile look alike with respect to color, shape, and size.
2. No dirt will be associated with the galleries and workings, and the workers will hollow out the infested item from cover to cover. The galleries are smooth and clean. Workers will eat winter and spring wood and will not necessarily eat with the grain of the wood.
Mouse damage to library materials usually results from their habit of chewing materials for nesting purposes and urinating and defecating on the materials (Figure 34). Mouse droppings (Figure 31) are smooth, dark, and usually pointed. Stains result from mice urinating on materials. Chewing damage can be recognized by the existence of a mouse nest within the immediate vicinity of the damage (Figure 35). Sometimes teeth marks will be left in the materials. Rodents have two incisor teeth on the upper and lower jaws. Distinct, double bite marks are an indication of mouse damage.
The kind of damage inflicted by mice can also be done by rats, but is encountered much less frequently. Rats generally nest outdoors in earthen burrows and do not normally damage materials directly. However, they will urinate and defecate on materials. Rat droppings (Figure 36) are large and oval in outline and will be found in quiet, protected corners of a room. Occasionally teeth marks may be found in the damaged materials where the upper and lower incisors have left their imprints, which will be much larger than those of a mouse.
FIGURE 36. - A comparison of the droppings of the house mouse and the Norway rat. Rat droppings are large, with blunt or rounded ends.
