Scarab beetles (family Scarabaeidae) are a massive and diverse group found on every continent except Antarctica. Despite their sometimes large size and formidable appearance, they are not a threat to human health and are incapable of inflicting serious injury. Their primary ecological roles involve decomposition, pollination, and sometimes agricultural damage, not confrontation with people.
What Defines a Scarab Beetle
The Scarabaeidae family is one of the largest groups in the insect kingdom, encompassing over 35,000 described species worldwide. Scarabs share several distinguishing physical characteristics, including a stout, robust body shape that is often oval or rounded. A defining feature is their antennae, which terminate in a unique lamellate club structure used to sense odors. This family includes rhinoceros beetles, dung beetles, June bugs, and chafers.
Assessment of Human Health Risks
Scarab beetles lack the specialized biological defenses necessary to harm humans, such as venom or potent stinging apparatuses. Unlike wasps or bees, they do not possess a stinger for injecting toxins. Their mouthparts are designed for chewing plant matter, dung, or decaying material, not for piercing human skin.
The largest species, such as rhinoceros beetles, may use their strong mandibles or horns defensively if handled. This action is typically a non-injurious pinch or nip that is startling rather than painful. Scarabs are not recognized as vectors for major human diseases like malaria or Lyme disease.
Certain dung beetle species can occasionally be intermediate hosts for parasitic worms (helminths) that affect cattle and humans. This transmission risk is related to ingesting contaminated beetles or their larvae, not through direct contact. The possibility of an allergic reaction to insect detritus exists, but this is a generalized environmental sensitivity, not a specific danger unique to the scarab family.
Scarabs as Damage Pests
While scarab beetles are harmless to people, certain species are defined as pests due to the significant damage they inflict on property and agriculture. This damage is primarily caused by the larval stage, commonly known as white grubs or curl grubs. These C-shaped larvae live underground and voraciously consume plant roots, especially those of turfgrass.
A heavy infestation of grubs causes severe damage to lawns, resulting in large, irregular brown patches of dead grass. The grass can sometimes be lifted and rolled back because the roots have been entirely severed. Grubs also damage root vegetables, such as potato tubers, and infest the roots of potted ornamental plants.
The adult forms of species like the Japanese beetle are also highly destructive, feeding on the aerial parts of plants. These adult beetles practice skeletonization, chewing the tissue between the veins of leaves until only a skeletal structure remains. Other species damage trees by chewing the bark, while various chafers feed on flowers, fruits, and foliage, posing a substantial economic threat.