Beetles belong to the order Coleoptera, recognized as the largest order in the animal kingdom. With an estimated 400,000 species described worldwide, they represent nearly 40% of all known insect species. They are characterized by hardened forewings, called elytra, which protect the membranous hindwings used for flight. Beetles inhabit nearly every terrestrial and aquatic environment, and their interaction with humans spans from beneficial to potentially harmful.
The General Safety Rule
The vast majority of beetle species pose no threat to people; many are ecologically beneficial as decomposers or pollinators. Most beetles do not possess stingers and are not known to transmit diseases to humans. Biting is rare, occurring almost always as a defensive reaction when the beetle is handled or provoked. This defensive biting results in minor, temporary discomfort rather than serious injury. Their primary defenses involve chemical deterrents or camouflage, meaning most encounters are entirely harmless.
Beetles That Pose Direct Health Risks
A small number of beetle species employ chemical defenses that can cause pain or injury upon contact. The most recognized are Blister Beetles (family Meloidae). They do not bite or sting; instead, they release a highly irritating substance called cantharidin when crushed or rubbed against the skin.
Cantharidin is a colorless, odorless compound that causes painful blistering and skin irritation known as contact dermatitis. The resulting welts are a localized reaction and are not life-threatening to humans. However, ingesting the beetles can lead to severe gastrointestinal distress and kidney damage, and it can be fatal to livestock if consumed in contaminated hay.
Larger beetle species may pose a mechanical threat if handled carelessly. Beetles like Longhorned beetles or female Stag Beetles possess powerful mandibles used for chewing wood or fighting. If threatened, they can deliver a defensive pinch or bite strong enough to cause noticeable, temporary pain and swelling. This mechanical injury is only a risk when the beetle is physically provoked.
Beetles That Cause Property Damage
Beetles are most destructive through economic damage to property and stored goods. Wood-boring beetles, such as powderpost beetles and the common furniture beetle, are concerning to homeowners. Their larvae, often called woodworms, bore extensive tunnels and feed on starches within structural wood, furniture, and flooring.
This feeding activity compromises the structural integrity of wooden objects. Damage is often detected only by small, circular exit holes and piles of fine, sawdust-like excrement, known as frass. The damage is long-term and costly to repair, especially when species like the old house borer infest construction wood.
Other species threaten household textiles and stored food supplies. Carpet beetle larvae feed on natural fibers like wool, silk, leather, and pet hair, causing irregular holes in clothing and carpets. Shed larval skins and hairs can also trigger allergic reactions. Weevils, a type of beetle characterized by an elongated snout, are notorious pantry pests, infesting grains, flour, and dry goods, leading to contamination that requires discarding the food.
Avoiding Unsafe Encounters
Preventing undesirable interactions involves simple steps focused on limiting contact and reducing available resources. Since chemical defense is triggered by handling, never touch or crush unfamiliar, brightly colored beetles. If a beetle must be removed from a living space, use a gloved hand or a piece of paper to safely relocate it outside.
To prevent property damage, household maintenance is the most effective defense. Regularly vacuuming carpets and upholstered furniture helps remove carpet beetle eggs and larvae, which feed on organic debris. Sealing cracks in exterior walls and storing pantry items in airtight containers prevents access for wood-boring species and stored product pests. Inspecting firewood and untreated wood before bringing it indoors also minimizes the risk of introducing wood-boring larvae.