Black Carpet Beetle Facts, Identification and Control

Scientific Order: Coleoptera

Scientific name: Attagenus unicolor

Appearance

Size: Less than ¼ inches long, pill-shaped
Color: “Unicolor” is derived from the Latin “One color”, a reference to the fact that the black carpet beetle is uniformly black or very dark brown, with shiny, shell-like eltrya. Adult black carpet beetle legs and antennae may look slightly lighter brown than its body.

Other Characteristics

Adult black carpet beetles are very proficient flyers.
Black carpet beetle larvae resemble caterpillars. They’re vaguely cigar or carrot-shaped, and look slightly longer and more narrow than their adult counterparts. They lack the wings, eltrya, or legs of adult carpet beetles, and have hard, shiny, smooth bodies that are black, reddish-brown, or burnt orange.
Black carpet beetle larvae have a distinctive tuft of long, curled, golden-brown hair protruding from their tail-end. The body of the larvae tapers toward the tail.
At the beginning of each step in their life cycle, black carpet beetles may appear pale or even white. The pest darkens very quickly with age, becoming black after only a few days in its latest form.

Diet

Despite the name, black carpet beetle larvae feed on a wide variety of organic materials. They’re associated with carpeting because the damage their feeding inflicts on carpeting tends to be the most destructive. They’re known to eat large, irregular holes through fabric fibers. This damage only slightly weakens the fabric at first, but over time it can ruin clothing, furniture, or even larger fabric products.
Carpet beetles eat almost any type of animal product, including leather, wool, silk, feathers, hair, and other organic fibers. Carpet beetles do not infest or feed on synthetic fibers.
Carpet beetles will eat through synthetic materials to get to partially organic materials, however, so poly-cotton or wool blends won’t be spared. In fact, because they can’t process synthetic fibers into energy, carpet beetles may inflict more damage on polysynthetic fabrics as they attempt to get meet nutritional requirements.
In a pinch, carpet beetles will also infest and damage natural stored food products, such as cereals, nuts, dry pet food, dried meat, grains, flour, or spices. Like pantry moths, they may even lay eggs on or inside food products.

Behavior

Adult black carpet beetles are attracted towards light and often land or swarm on window sills, ledges, lamp shades, or lamp posts.
Like pantry moths, black carpet beetles actually do all their human-significant damage in their larval form. Carpet beetles do all of their eating and growing in this form, and chew their way through a wide variety of stored foods and fabrics in the process.

Ironically, black carpet beetle larvae avoid light, preferring to shelter in dark, confided, and warm places where they can easily access food.
Beetle larva’s day-to-day activity consists largely of resting during the day and slowly moving back toward food to feed at night. If their food source is in an environment that’s always dark, the beetles will feed semi-continuously.

Reproduction

Black carpet beetle reproductive season begins as soon as outdoor temperatures reach consistently above-freezing temperatures. Carpet beetles can continuously mate and undergo complete life cycles as long as the temperature of their environment remains warm. Black carpet beetles undergo a complete metamorphosis in four distinct stages:

Egg Stage

After mating, female black carpet beetles seek a sheltered area near a plentiful larva food source where they can lay their eggs. Females can lay as many as 90 eggs at a time. These eggs are tiny, pearly-white, and can stick to sheer surfaces.

The speed at which the beetle eggs incubate and hatch depends on the temperature of the environment where they were laid. In warm environments, the eggs may hatch in as few as 6 to 11 days.

Larval Stage

Black carpet beetles spend much of their lives as larva, and they do the most damage at this stage. Beetle larvae seek out and begin feeding on the nearby food sources as soon as they hatch. Larvae eat continuously, only stopping to shed their skin so they can continue to grow. Larvae must shed their skin numerous times as they mature. Unlike their adult counterparts, black carpet beetle larva actively avoid light, and will stay in shade and shelter for the entirety of their development if possible.

The exact number of times larvae shed their skin depends on how quickly the beetle is able to store enough energy to pupate. The amount of time it takes a larva to pupate is determined by the quality of the larva’s food source, as well as the temperature and relative humidity of their environment. The Black carpet beetle larval stage can last anywhere between 166 to 639 days. Temperatures must be above freezing for the beetle to enter the pupal stage, so many black carpet beetles naturally overwinter as larvae.

Pupal Stage

During the pupal stage, the larvae stop eating and enter a completely dormant state while they undergo their final metamorphosis into adult black carpet beetles. Larvae tend to look for dark, sheltered places to pupate, and they can only enter the state if they’re warm enough.

The black carpet beetle pupal stage is brief, generally lasting only 6 to 24 days. Unlike many metamorphosing insects, black carpet beetles do not spin a cocoon of silk or thread before they pupate. Instead, they simply pupate from inside the last larval skin.

Adult Stage

Ironically, adult black carpet beetles don’t eat or inflict damage on any structures or materials. In fact, adult carpet beetles generally only live long enough to reproduce and lay eggs before they die off. Unlike larvae, adults can fly and are attracted to light. Oftentimes, adult carpet beetles will find mates after swarming around a light source.

Though they frequently die out after as few as 4 to 8 weeks, adult black carpet beetles may continue living for several months, provided they have pollen to consume. Adults that continue to live may reproduce continuously until the weather cools.

A black carpet beetles’ entire life cycle, from egg to adult, may complete in as few as two months under ideal circumstances.

Signs of Infestation

Black carpet beetle larvae eat large, irregular holes through their food sources. These holes tend to be particularly noticeable on fabric products such as clothing, linens, and carpeting. Look for small holes that grow larger slowly, as well as a series of small holes in a localized area. These small holes may eventually join into single, larger holes, as well.
Beetle larvae also leave behind shed skin on or near their food sources as they molt. This shed skin will be difficult to spot and very flakey, so it could easily break down into a dust-like material. Dry, flakey material left on clothing, carpet, or other fabric might be the shed skin of a beetle.
Adult beetles lay their eggs on sources of heat that are close to a food source. Usually, they’ll seek out heating vents, boiler rooms, furnaces, or other heat sources. They lay their eggs in cracks and crevices or other secluded locations, where the eggs will be concealed and safe. Black carpet beetle eggs are tiny, round, and pearly white.
Remember that black carpet beetles don’t just infest carpet or fabrics; they’re also a considerable stored food pest. The beetle prefers dark, warm food storage areas such as pantries or cupboards. Look for signs on grains such as cereals and pastas, as well as other dry food such as dried meat or pet food.

Treatment and Prevention

Start by carefully inspecting any areas you suspect harbor beetles. Black carpet beetles can be difficult to see and they tend to live in nooks and crannies, so be thorough. Check dark areas such as basements, pantries, boiler rooms, and attics especially carefully. Remember to inspect both organic animal products and stored food products for signs of infestation.
Vacuum up any black carpet beetles, larvae, or eggs you happen to find as you find them. Dispose of the vacuum bag into a dumpster outside your building when you’re finished. Throw out any infested stored food you find at the same time. If you find signs of infestation on clothing or fabrics you can’t dispose of, it may be possible to kill hidden eggs or larvae by freezing the item.
Pet hair and lint are often the first food sources that attract beetles into a home in the first place. If you have pets, be sure to vacuum up the hair they leave behind frequently, and keep an eye on their bedding for beetles or other pests. Wash your pet’s fur regularly to prevent beetles from hiding it to infest your building at a later time.
Beetles often enter a building after they’re brought in accidentally. Check boxes and bags brought into your building, especially if you’re transporting fabrics or dry food. Consider inspecting clothing items and other fabrics before you rearrange or store them inside your building. Periodically double-check on materials you’ve recently brought inside, just in case you missed signs of infestation the first time you checked.

More Information

Cornell University Dept. of Entomology Insect Diagnostic Laboratory “Beetles Infesting Woolens” fact sheet
Cornell University Cooperative Extension of Rockland County Carpet Beetles fact sheet
Penn State Dept. of Entomology Black Carpet Beetle fact sheet
University of California Agriculture & Pest Management Program “How to Manage Carpet Beetles” page
University of Florida Entomology & Nematology “Featured Creatures” black carpet beetle page
University of Maine Cooperative Extension Carpet Beetles fact sheet
Colorado State University Extension Carpet Beetles fact sheet