Why Thousands of Winged Termites Suddenly Emerge After the First Big Rain

Nature · Published 29 September 2026 Swipe more like this →

In short: Following the first significant rainfall of the season, western subterranean termites swarm in massive numbers. These winged insects, known as alates, face a gauntlet of predators before they can shed their wings and establish new underground colonies. Discover the perilous journey these termites undertake to ensure their species' survival.

In California, the annual emergence of western subterranean termites is triggered by warm, windless days occurring shortly after the first major rain that concludes the dry summer. During this event, winged alates push through softened soil, emerging from cracks in roads or holes in tree stumps. While soldier termites with large heads stand guard to defend the swarm, the alates are highly vulnerable to predators like ants, spiders, and birds that pick them off in large numbers.

The primary purpose of these alates is reproduction. Once a male and female find each other, their wings break off, and they quickly retreat into the earth to begin a new colony as king and queen. They will eventually produce thousands of eggs. It is the worker termites, born later, that forage for cellulose sources like dead trees or structural wood in homes. These workers return to the nest to feed the king, queen, and young, using mud and saliva to build protective shelter tubes.

These shelter tubes are essential for the survival of the colony, as termites desiccate easily and require a moist environment. While seeing flying termites inside a home can indicate an existing infestation, the presence of these mud-based tubes connecting wooden structures to the soil is a more common sign of trouble. All types of termites, including subterranean, drywood, and dampwood, produce alates to expand their populations, though only a fraction of any colony possesses the ability to fly.

The process is a high-stakes gamble for the colony. By sending alates to mate with those from nearby colonies, the termites ensure genetic diversity and expansion. Despite the danger posed by predators during the initial flight, this cycle of emergence and colonization is a fundamental mechanism for the persistence of termite populations across the region.

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