IPM for Silverfish, Firebrats, and Booklice in Schools
Introduction
Silverfish, firebrats, and booklice are grouped together because they occur in the same or similar habitats. They prefer a dark, moist environment and require a large supply of starchy foods or molds. Although they are found in closely associated environments, silverfish and firebrats belong to an entirely different insect order than booklice. Each of these insects are considered to be nuisance pests that can feed on wallpaper pastes, natural textiles, books, and manuscripts. They also feed on mold that grows on various surfaces.
Silverfish, firebrats, and booklice can live indoors or outdoors. They are frequently introduced into a structure with storage boxes, but they can also wander in from outside. They are fast-moving and can travel throughout buildings. Once these insects find a good source of food, however, they stay close to it. In general, they do very little damage, but they may cause people to take radical action based on their fear of insects.
Silverfish and Firebrats
Identification and Biology
Silverfish and firebrats belong to an order called Thysanura. Insects in this order are considered to be some of the most primitive insects alive today. Insects in the order Thysanura have characteristic, three long tail-like appendages attached to the tapered posterior end, each about as long as the body. These insects are wingless, with chewing mouth parts, long antennae, and their body is covered with scales. The mouthparts of silverfish and firebrats are used for biting off small particles or for scraping at surfaces. The most common species inhabiting buildings are in the genus Lepisma (silverfish) and the genus Thermobia (firebrat). The silverfish (Lepisma saccharina) is about 1/2 inch long when fully grown, and covered with silvery scales. It is grayish to greenish in color and its body has a flattened-carrot shape. The firebrat (Thermobia domestica) has a mottled appearance with patches of white and black, and is shaped similarly to silverfish.
Silverfish and firebrats eat material high in protein, sugar, or starch, including cereals, moist wheat flour, starch in book bindings, sizing in paper, and paper on which there is glue or paste. These insects often attack wallpaper, eating irregular holes through the paper to get to the paste. Silverfish may bite very small holes in various fabrics, including cotton, linen, and silk, even though they cannot digest either linen or cotton. Firebrats will feed extensively on rayon, whereas silverfish usually damage it only slightly.
Characteristics of the silverfish, Lepisma saccharina:
- lay eggs in any season and take 19 to 43 days to hatch
- the life cycle from egg to adult is three to four months molting at least three to four times
- prefer moist areas (75 to 97% humidity) and moderate temperatures (70° to 80° F)
- active at night or in dark places and may be found throughout the building
- adults lay one to three eggs per day and live two to 3.5 years; the biotic potential of one female is 1,500 to 3,500 offspring
- adults molt up to 50 times
- leave yellowish stains on fabric
- outdoors, live in nests of insects, birds (especially pigeons), and mammals, and under the bark of trees
Characteristics of the firebrat, Thermobia domestica:
- lay eggs in cracks and crevices, which hatch in 12 to 13 days
- the life cycle from egg to adult is two to four months, nymphs molt at least 12 times
- prefer moist areas with temperatures above 90° F
- adults lay 50 eggs per batch and live for two to three years; the biotic potential of one female is 9,050 offspring
- adults molt up to 50 times
- active at night or in dark places
- found where heat and starches are present (for example, in bakeries); also found in furnace rooms, steam pipe tunnels, and partition walls of water heater rooms.
Booklice
The most common booklouse (Liposcelis spp.) is a small, grayish, soft-bodied insect with chewing mouthparts and long antennae. It has a very flat shape superficially resembling the shape of head lice. The common house-dwelling booklouse is wingless or its wings are reduced to small scale-like, non-functional wings. The size of an adult is approximately 1/25 to 1/12 inch. Booklice cause little direct damage to plants and wood because they feed chiefly on mold. They are found commonly in confined areas like the bindings of books, where they eat the starch sizing in the bindings and along the edges of pages.
Characteristics of booklice:
- eggs hatch in 21 days
- the life cycle from egg to adult is around 110 days, with the insect molting two to three times
- adults lay 20 to 50 eggs depending on seasonal conditions, and live 24 to 110 days
- the biotic potential is 120 to 456 offspring per female
- prefer warm, moist conditions that are conducive to the growth of mold and mildew and require humidity of at least 60%
- found in books and paper products
- sometimes found on houseplants where they may be feeding on honeydew (a protein-rich substance excreted by plant-eating insects such as aphids), or more likely, on the sooty mold that grows on the honeydew
Detection
Silverfish are found in bookcases, on closet shelves, behind baseboards, wallpaper, window or door frames, wall voids, attics, and sub-floor areas. They prefer bathrooms and kitchens because of the moisture associated with these areas. Firebrats will be found in similar but warmer areas. Both silverfish and firebrats molt as many as 50 times during their adult lives, therefore the appearance of cast skins may be a useful detection tool. Booklice prefer damp and warm habitats, so they are most numerous during the spring and summer. New buildings are not immune to infestations of booklice. It is essential that conducive conditions to booklice development be identified before control measures can be initiated. Silverfish, firebrats, and booklice can be detected by placing sticky cockroach traps in the area where damage is occurring. When the insects are caught, they should be preserved in alcohol for professional identification.
Physical Control
Dehumidifying
Dehumidifying reduces the moisture content of the air that these insects find essential. Some methods for dehumidifying include:
- Mend leaking pipes.
- Ventilate closed rooms and attics.
- Eliminate standing water.
- Use a dehumidifier
- Use anhydrous calcium carbonate or silica gel.
Vacuuming
Regularly vacuuming cracks and crevices with a narrow vacuum tip also can be a good method to physically remove these insects from their harborages.
Removal of food
Excess food material should be eliminated. Food sources that can not be removed should be sealed in containers.
Trapping
Silverfish can be trapped in small glass jars, with the outside of the jar wrapped with masking tape so the insects have something to grip as they climb up. Set the jars upright in areas where silverfish have been seen. Silverfish can also be trapped on cockroach glue board traps.
Eliminating Harborage Sites
Wherever possible, potential hiding areas should be sealed with caulk, especially around windows, cabinets, and moldings. Increasing the lighting makes harborages less hospitable. Removal of leaf litter from around the home can decrease the chance of an outside invasion.
Drying Stored Articles
Periodic airing and drying of articles stored in damp areas may help reduce the mold on which these insects feed. Disposing of moldy articles is often the simplest way of removing an infestation in an area.
Chemical Control
Diatomaceous earth, borate-based insecticidal dust products, and silica aerogel can be used to kill these insects. Diatomaceous earth and borate-based products must be kept dry to be most effective, but silica aerogel will work under damp conditions.
Residual insecticides should be applied to the area where silverfish, firebrats, and booklice are commonly seen. Residual insecticides and dusts are frequently used in combination and their effectiveness can be increased with a flushing agent usually a pyrethrin-based insecticide.
Some insecticides are registered for control silverfish and firebrats and/or booklice indoors, whereas others are registered for outdoor use only.
Edited by: Thomas E. Powell, University of Florida.
Originally written by: S. Darr, T. Drlik, H. Olkowski, and W. Olkowski
Photographs and Graphics: University of Florida
Published: May, 1998
