Earwigs are instantly recognizable by the prominent pincer-like appendages at the end of their abdomen. They often appear in large numbers, leading many to assume they are social insects that travel in groups. This observation is misleading, as the insects are not technically group-living organisms in the same way ants or bees are. While earwigs spend most of their adult lives as independent foragers, they possess an unusual tendency to gather in high concentrations that mimics a social structure. This habit of temporary grouping, alongside a unique period of maternal care, explains why they are so frequently observed clustered together.
Are Earwigs Truly Solitary Insects?
The definitive biological answer is that earwigs are not “social” insects, nor do they travel in a cooperative “pack.” True social insects, like termites, ants, or certain wasps, exhibit a high degree of cooperation, reproductive division of labor, and overlapping generations living together. Earwigs, which belong to the order Dermaptera, lack these complex traits and are classified as facultatively social or subsocial, meaning their group behavior is limited and temporary.
Most adult earwigs operate as solitary individuals, foraging independently during their nocturnal activity periods. Their life cycle involves individual survival and reproduction without relying on a colony structure for food or defense. The term “pack” in an entomological context implies a level of shared purpose and communication that earwigs simply do not exhibit.
Why Earwigs Gather in Large Numbers
The common sight of multiple earwigs clustered together is an example of aggregation, which is a response to favorable environmental conditions rather than social cooperation. Earwigs are nocturnal and strongly thigmotactic, meaning they seek out tight, dark, enclosed spaces for shelter during the day. This behavior often leads many individuals to choose the exact same optimal micro-environment, such as under a damp piece of wood, a flat stone, or a pile of mulch.
The primary driver for these groupings is the need for moisture, as earwigs must actively seek out damp environments to prevent desiccation. These preferred spots are often found near decaying organic matter, which serves as a readily available food source for these omnivorous scavengers. The resulting cluster of individuals is therefore an accidental consequence of many solitary insects responding to the same optimal conditions.
Adding to this phenomenon, the European earwig (Forficula auricularia) has been shown to secrete an aggregation pheromone that attracts other earwigs to the same location. This chemical signal encourages more individuals to gather, effectively reinforcing the density of the cluster. This chemical grouping helps the insects retain warmth during overwintering periods.
The Unique Case of Maternal Grouping
While most of their adult life is solitary, female earwigs provide a notable exception by exhibiting a distinct form of maternal care, a trait uncommon among non-social insects. The female will excavate a small underground cell or nest where she lays a clutch of eggs. She then remains with the eggs, actively guarding them from predators and even her own mate.
The mother also performs a cleaning behavior, periodically licking the eggs to remove fungal spores and deposit protective hydrocarbons, which significantly increases the hatching success rate. After the nymphs hatch, the mother will continue to guard them until after their first or second molt, a period of temporary family grouping. Once the young nymphs mature and become independent foragers, the mother-offspring bond dissolves, and the young disperse to begin their solitary adult lives.