The earwig, an insect belonging to the Order Dermaptera, is easily recognized by the prominent, forceps-like appendages, called cerci, extending from its abdomen. This insect group comprises approximately 2,000 species worldwide. Earwigs are primarily nocturnal, seeking dark, moist environments like leaf litter, soil, and under bark during the day. They are omnivorous, acting as scavengers on decaying plant matter, though they also consume small live insects.
Vertebrate Animals That Hunt Earwigs
Earwigs serve as food for a variety of larger animals, especially those that forage on the ground. Birds are among the most common daytime predators, with species like American robins, starlings, and chickens actively flipping leaf litter and soil to locate them. These ground-feeding birds consume earwigs in large quantities, helping to regulate local populations.
Small insectivorous mammals also rely on earwigs as part of their diet. Shrews and moles, with their keen sense of smell, frequently encounter and consume earwigs as they tunnel and forage through the ground. Bats have also been documented preying on earwigs, capturing them during their nocturnal flights.
Amphibians and reptiles also target earwigs, often due to their shared habitat and nocturnal activity patterns. Toads and frogs are effective hunters, as they are active at night when earwigs leave their hiding spots to feed. Lizards, though diurnal, will opportunistically consume earwigs found hiding in damp, shady areas.
Specialized Invertebrate Predators and Parasites
Earwigs face threats from smaller, specialized invertebrate predators and parasitic organisms. Predatory arthropods such as large wolf spiders, centipedes, and ground beetles actively hunt earwigs in the dark, damp environments where they seek shelter. These hunters are quick and possess powerful mouthparts or venom to subdue their prey.
A different kind of threat comes from parasitic insects, notably certain species of tachinid flies. These flies are endoparasites; their larvae develop inside the earwig host after the adult fly lays an egg on or near the insect. Species like the tachinid fly Triarthria setipennis have been studied as a successful biological control agent against earwigs.
Earwigs are also susceptible to microscopic parasites, including nematodes and fungi. The roundworm Mermis nigrescens occasionally parasitizes earwigs that accidentally ingest its eggs while feeding on plant matter. Earwigs can also host parasitic fungi from the Order Laboulbeniales, and their eggs and nymphs are subject to cannibalism by other earwigs.
Earwig Strategies for Predator Evasion
Earwigs employ several behaviors and physical adaptations to avoid becoming prey. Their most effective passive defense is their strictly nocturnal behavior, which allows them to avoid many diurnal predators like birds. By spending daylight hours concealed in tight crevices, they reduce their visibility and exposure.
The distinct cerci, or pincers, serve as a primary line of mechanical defense against smaller threats. When disturbed, an earwig will bend its abdomen forward over its body, raising the cerci in a menacing display to intimidate or physically grasp an attacker. Both male and female cerci are used to pinch or deter attackers.
When physical defense is not enough, earwigs can deploy a chemical defense by releasing a foul-smelling, often yellowish, exudate from glands on their abdomen. This secretion contains benzoquinone derivatives, which are irritating to many predators. This defensive fluid is multifunctional, also exhibiting antimicrobial and nematicidal activity.