The Top 5 Fabric and Museum Insects

By Ethan Estabrook, BCE, Research Entomologist and Product Support at Insects Limited

Up to 54% of museums and historic homes have reported damage from insects. Textiles, animal hides, taxidermy, wood works, natural fibers (like wool and cotton), books, and paintings all contain material that insects can exploit and do irreversible damage to.

In this article, I am going to break down fabric and museum insects into the top five most encountered species – the webbing clothes moth, varied carpet beetle, silverfish, cigarette beetle, and powderpost beetle.

First I would like to share a couple stories of why knowing the insect and having a good Integrated Pest Management (IPM) program is crucial to protect and ensure the continued longevity of important historical artifacts. Ss well as how some IPM programs can be difficult to implement with different cultural ideologies.

The first story is from David Pinniger, an IPM specialist in the United Kingdom, who shared his story at a pest management working group of how clothes moths destroyed the last remaining skin and feathers of the now-extinct dodo bird. The remains of the bird were hidden in a display case in the museum beneath an artistic rendering of how the bird may have looked when it was alive. When the museum staff opened the case after several years to do some cleaning, there was nothing left of the specimen except the bones.

The other story was shared by Elénore Kissel, a conservator in Paris. She was working in Tibet with Tibetan monks. Their task was to save some ancient tapestries from destruction by carpet beetles. The monks’ religious view of reincarnation left them uncomfortable with physically killing the beetle larvae and adults on the tapestry, so they spent several weeks removing each insect by hand with tweezers and releasing them far away from the monastery each night.

Webbing Clothes Moth

The number one most common and detrimental fabric and museum pest is the webbing clothes moth, Tineola bisselliella. Webbing clothes moths can be identified by their single tone of creamy white to shiny gold color with no spots. The case making clothes moth is a similar fabric and museum pest but have small spots on their wings. Adult moths live for 15-30 days where upon mated females can lay 40-50 eggs individually or in groups. Eggs hatch in 4-10 days in warmer months and up to 30 days in cooler months.

The larvae feed and become mature in 35 days or as long as 30 months depending on food quality, temperature, and humidity. Pupation will occur in infested materials. Adults will emerge from the pupae in 8 to 40 days depending on temperature. Signs of clothes moth infestation include granular frass the size of ground pepper on or around items they are feeding on such as fabric, furs, taxidermy mounts, hanging clothes in closets, wool rugs, carpets, and upholstered furniture when rips or tears expose stuffing. Larvae can cause serious damage to wools, furs, and feathers.

Larvae create white webbing tunnels, but these are not always present. Pupae cases can be found on the surface, within a pile of carpet and rugs, or underneath these materials.

Varied Carpet Beetle

The second most common fabric and museum pest is the varied carpet beetle, Anthrenus verbasci. Varied carpet beetles have a black to gray body with a varied pattern of white, yellow, and brown elongated scales on their elytra. The last three antennae segments are slightly enlarged and form a club shape. The female beetle will lay eggs in materials made with hair, feather, or insect parts. Larvae will feed off the food or fiber substance for about 7-10 months depending on environmental conditions. The life cycle on average will be 11 months and adults live for 30-45 days.

Adults actively fly when temperature is above 70 degrees Fahrenheit. Only larvae cause damage to plant, animal products, and textiles. Adult carpet beetles feed on pollen of flowing plants. The presence of cast or shed skins is a telltale sign of larval activity. Holes and frayed fibers in textiles may also be present. Adults are excellent fliers and are attracted to lights. Varied carpet beetles are commonly found in nests of bees, wasps, and birds, but can also attack, horn, wool, hair, silk, dead insects and is occasionally found in food and spices. The varied carpet beetle is a common household insect.

Silverfish

Third is the common silverfish, Lepisma saccharinum. Silverfish are light gray and have an elongated body with 3 long bristle-like appendages at the end of their abdomen.

Silverfish are found throughout the U.S. and are typically seen in moist, humid areas in the home, such as bathrooms, basements, and attics. A female will lay up to 100 eggs in her lifetime into small cracks and crevices.

When eggs hatch into nymphs, they are whitish and look like small adults. As they molt, young silverfish develop a greyish appearance and a metallic shine, eventually becoming adults after three months to three years. They may go through 20 to 50 molts in their lifetimes and continue to molt after reaching adulthood.

Silverfish can digest cellulose due to the enzymes that in their midgut. These could include book bindings, carpet, clothing, dandruff, glue, hair, paper, photos, plaster, and sugar. Other substances they eat include cotton, dead insects, linen, silk, tapestries, leftover crumbs, or even their own molted exoskeletons. Silverfish are known to live for a year or more without eating if water is available.

Cigarette Beetle

Fourth most common is the Cigarette beetle, Lasioderma serricorne. Cigarette beetles can be identified from drugstore beetles by the many serrated teeth antennae. The female beetle will lay up to 100 eggs during a 2-4 week life span. Larvae will tunnel through the food product for about 4-5 weeks. The average life cycle will take 6-8 weeks depending on temperature and humidity. These beetles are excellent flyers and are most active in the late afternoons.

Packages and food products infested with these beetles usually have shot holes where adults have emerged from pupation. Both adults and larvae cause product damage. Adults are excellent fliers and are attracted to lights. These beetles are commonly found in tobacco and other processed foods such as spices, flour, dog food, but can also attack horn, wool, hair, hide, pharmaceuticals and even book bindings. It is a common household pest.

Powederpost Beetle

Coming in at number five is the powderpost beetle. The “Powderpost beetle” is a term used to describe several species of small insects that damage wood to a flour-like powder. Larval development takes place entirely under the wood surface. The developing grub-like larvae damage wood as they create narrow, meandering tunnels as they feed. Infestations can be identified by noticing powder, accompanied by small, round “shot holes” on the wood surface.

These “shot holes” are exit holes where adult beetles have chewed out of the wood after completing their development. Newly emerged adults’ mate and lay eggs on or below the surface of bare, unfinished wood. The eggs hatch into tiny larvae that bore into the wood, completing their life cycle. Customers are more likely to see damage, rather than the beetles themselves, because the adults are cryptic and active mainly at night. Occasionally, powderpost beetles may are found near damaged wood, or on windowsills since some are attracted to light.

The three most destructive wood-boring insect groups that can reinfest wood products are the lyctids which are the true powderpost beetles, anobiids or the furniture beetles, and bostrichids or the false powderpost beetles. Lyctids attack wood products manufactured from hardwood trees such as oak, ash, walnut, hickory, poplar, cherry, tropical hardwoods, and bamboo. Anobiids attack both hardwoods and softwoods, usually with higher moisture content. Bostrichids attack mainly hardwoods but have been seen on some softwoods.

Monitoring for Insects

Monitoring for insects provides valuable information, such as the presence of insects, insect species, population trends, and locations of infestations. Blunder traps capture pests that are moving between areas while baited traps use food or pheromone attractants to lure specific species of insect to a trap. Different styles of traps and attractants are used to monitor different species.

For example, hanging traps are designed to capture flying insects while floor traps are designed to capture crawling insects. Varied carpet beetles can be best monitored by a food lure and pheromone lure in a floor trap. Moths like the Webbing Clothes Moth and Casemaking Clothes Moth are clumsy flyers can be monitored using hanging or floor traps with a pheromone lure.

There are several ways to treat an active pest infestation at museums and historic homes. The most appropriate method will depend on a variety of factors such as the type of collection, size of infestation, institutional capabilities, and budget.

What Are Some Insect Treatment Options?

• Isolation or Bagging (Placing item on white paper in polyethylene bag. Waiting a few weeks then inspect for signs of insect activity such as live insects, cast skins, frass, or webbing)

• Freezing (Store items in freezer at -20F for 72 hours)

• Anoxic Treatment (Reducing oxygen concentrations to 0.5% for 21 days)

• Heat Treatment (Storing items in an oven or solar bag at 130 – 140F for 3 hours)

• Fumigation (Using Phosphine at 500 – 1,000 ppm for 72 hours above 70F or Sulfuryl fluoride at 500-1,000CT (depending on insect species) for 24 hours above 80F.)

• There is also the option of other Pesticides such as pyrethroids, insect growth regulators, organophosphates, boric acid, or diatomaceous earth. Make sure to read and follow the label!

It is important to Start with the Insect First!

Identifying the insect and understanding their biology is the first step to an effective integrated pest management program.

Once the fabric or museum insect has been identified, inspect areas for ideal food sources such as wools, furs, or feathers.

Pheromone lures and traps are great tools to monitor and help identify the source of infestation.

Finding and treating the source can help pest management professionals solve a difficult pest problem to help protect artifacts of historical importance.

If you have any fabric and museum insect or pheromone questions, you can contact me at E.Estabrook@InsectsLimited.com.

Insects Limited, an Insect Pheromone Company

Insects Limited, Inc. researches, tests, develops, manufactures and distributes pheromones and trapping systems for insects in a global marketplace. The highly qualified staff also can assist with consultation, areas of expert witness, training presentations and grant writing.

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