Beetle Facts, Identification and Control
Scientific Order: Coleoptera
Size: Varies widely based on species. The largest species, such as Titanus giganteus and Goliathus goliatus, can be over six inches long. The smallest species, in the Ptiliidae family, can be less than a millimeter long. The most common New York beetles are the black carpet beetle, which are 2.8 to 5 mm long, and the confused flour beetle, which are about 1/7-inch long.
Color: Different species of beetle may be vibrant, bright colors, or simple blacks or browns. Regardless of species, beetles tend to be shiny because of their hardened, thick forewings and shell-like wing covers. Common beetles in New York tend to be black, dark brown, or reddish-brown.
Different beetles species evolved differently, to adapt to their environments. Species may differ greatly in appearance, ability, and consequently, behavior.
Many beetles are adept burrowers or tunnelers. Larval beetles can burrow through hard matter such as wood and ground to feed, take shelter, and grow. The invasive asian longhorned beetle destroys hardwood trees such as maples by burrowing through them as larva.
Beetles tend to be social insects, communicating through a variety of means. Many beetles live together eusocially, like bees or ants, and divide labor and reproductive responsibilities. Beetles that live in eusocial colonies develop specializations to better serve their colonies needs.
Some beetles are generalized omnivores capable of sustaining themselves on a wide variety of food sources. Others are highly specialized. Most beetles are poor fliers, preferring to search for food from the ground level or climb to reach places.
Beetles feed on virtually anything, including fabric, wood, furniture, plants, shrubbery, other insects, grains, garbage, or decaying organic matter. Different species have different preferences or dietary requirements.
Reproduction and Life Cycle
Beetles are members of the superorder Endopterygota, which means they undergo a four stage life cycle: egg, larva, pupa, and adult. This life cycle takes 21-27 days, or longer in winter. Different species of beetle reproduce in a variety of ways. Female-only species of beetles capable of reproducing without fertilization exist, but the most common form of fertilization is sexual mating.
After fertilization, the female lays eggs near food so that when the larva hatch they don’t have to search. Females may lay anywhere from 63 to 228 egg cases, which themselves can have 3 or more eggs inside them. Eggs typically hatch 4-6 days after they’re laid, though this varies species-by-species.
Beetles require a lot of energy and nutrients to develop into adults, so most of a beetle’s feeding takes place during its larval stage. Beetle larvae are largely defenseless, so they often feed by burrowing through a food source, providing them with shelter as well as sustenance. Beetle larvae feed until they grow too big for their larval skin. Then, they shed their skin in a process called “molting” so they can continue to grow. They repeat the molting process several times until the larva is fully matured.
When a larva has grown sufficiently, it enters the pupal stage. During this stage, the beetle is defenseless. Many beetles that burrow into their food sources or the ground dig out a “pupal cavity,” which they use for shelter while they complete this stage. The pupal stage lasts a minimum of four days, sometimes longer.
The pupal stage ends when the beetle’s adult exoskeleton, including its elytra, has sufficiently hardened. Then, the fully-formed adult beetle breaks out of its pupal skin. Adult beetles can live for over 230 days.
The beetle order’s scientific name, Coleoptera, means “folded wing” in Latin. It refers to their defining characteristic, which is that all beetles have a hardened and thickened pair of forewings, or wing covers, called elytra.
The elytra cover and protect beetle’s fragile flying wings. The elytra resemble a shell or pair of shells and cover most beetle’s entire back abdomen, with an opening in the middle where the two separate wing covers meet. When beetles take flight, their elytra lift to allow the thin flying wings beneath to unfold outward from the beetle’s body.
To identify a beetle, look for the elytra.The “true bug” order, Hemiptera, sometimes resemble beetles, but their wings are only partially hardened or thickened.
Another way to distinguish beetles from cockroaches or other kinds of insects is to look for chewing mouthparts. Beetles always have chewing, biting mouthparts, with sharp mandibles or “pincers.” Beetles use their chewing mandibles to breakdown and eat their meals of shrubs, trees, fabrics, or other woods.
Signs of Infestation
Beetles are considered a pest primarily because of their potential to eat and damage valuables. The types of beetles encountered in New York can be divided into three pest categories: food-consuming, fabric-consuming, and wood-consuming. Other beetles encountered in New York, such as the multicolored asian lady beetle, do not pose a direct threat to homes but may be considered a nuisance pest.
Food consuming: Look for signs of food tampering, especially in grain products like bread, cereal, dried fruit, flour,candy, bird seed, and nuts. Beetles often chew through cardboard, paper, or plastic packaging to get at the food inside. They may even live within packaging to stay sheltered and close to food.
Fabric consuming: You may begin to notice damage on furnishings or clothing made of wool, fur, or leather. Small holes may appear where beetle larvae chew through the fabric. These larvae target carpeting in particular, so examine your carpeting for signs of damage or grime. Early signs of damage may be difficult to make out, so don’t assume a small hole in a shirt or piece of furniture isn’t a problem.
Wood consuming: The most common wood-consuming beetle encountered is the powderpost beetle. The larvae of the powderpost beetle feed on cellulose found in wood. Female powderpost beetles deposit eggs in the cracks and crevices of wooden surfaces. The larvae burrow into wood, leaving holes about 1/8-inch in diameter. When the beetles finish pupating, they exit the wood, leaving behind sawdust. Check the legs and undersides of wooden furniture. Test them for structural weakness or softness.
It’s unlikely your home or business will be infested by Asian longhorned beetles, but if you see one, report it immediately. Asian longhorned beetles are an invasive species of wood-consuming beetle responsible for killing hundreds of New York’s ash, birch, elm, maple, and willow trees. See this map for info on the current suspected infestations in New York.
Treatment and Prevention
The best way to prevent beetle infestations in your home or business is to deprive them of the things that attract them. Beetles require food, water and shelter; if you can make sure they can’t get these, you’ll go a long way toward preventing any infestations.
Food Consuming: Keep at-risk foods such as grains and fruits in sealed hard plastic containers, not cardboard or paper packaging. Store bread in cabinets off the ground or in the refrigerator. Wipe up crumbs after every meal and do not leave food out on the counter or in the kitchen sink. Take garbage out daily.
Fabric Consuming: Dispose of clothing you don’t wear often. Launder clothing frequently and regularly. Consider washing clothes after a couple weeks, even if you haven’t worn them. Store clothing in a dry place with a consistent temperature. Keep clothing in sealed plastic, hangable bags. Vacuum carpet weekly, and consider steam cleaning once every couple of months.
Wood Consuming: Make sure all wooden furniture is treated and stained. Dispose of old or damaged wooden furniture. Beetles are particularly attracted to dusty and dirty furniture, so clean and inspect wood every now and then. Check for cracks, damage, or discoloration. If you find any, stress test the furniture to make sure it hasn’t been structurally damaged. Keep wooden furniture inside, in a room that doesn’t experience temperature variation or humidity.
Cornell University Insect Diagnostic Laboratory (several fact sheets about specific beetle species, including the ones covered here)
Penn State College of Agricultural Studies, Department of Entomology insect fact sheets (includes several common beetle species)
Identification of Beetles, a step-by-step guide by the Virginia Tech College of Agriculture and Life Sciences
Beetles of New York, (incomplete) database of New York’s beetles by insectidentification.org
New York State Department of Environmental Conservation information on insects and other species. Includes several species of beetle.