Residents across California have reported seeing unusually large swarms of dragonflies this summer, a phenomenon that experts attribute to warm monsoon storms earlier in the year. Sightings have been documented in the San Francisco Bay Area, Oakland, and Fresno County. Observers noted groups of up to 100 insects flying together in public parks and agricultural areas.
Kathy Biggs, a dragonfly expert and co-author of "Dragonflies of California," stated that the high numbers are likely wandering gliders, a highly migratory species. These insects appear in larger clusters when weather conditions, specifically warm spring rains and monsoon-driven pressure systems, facilitate their movement. Dragonflies use changes in air pressure to travel long distances and can reach flight speeds of up to 35 mph.
In agricultural regions like Fresno County, farmers reported an increase in dragonfly activity starting earlier this month. Joe Del Bosque, a local farmer, observed the insects flying 10 to 20 feet above his fields. He noted that the dragonflies act as a form of natural pest control by preying on aphids, whiteflies, and fruit flies that typically damage crops. Entomologists from the California Academy of Science noted that dragonflies are highly effective predators, with a hunting success rate exceeding 90%.
The scale of this event is linked to regional weather patterns rather than a permanent population shift. While California is home to approximately 70 dragonfly species, most are stationary. However, the migratory wandering gliders have emerged in concentrations high enough to be documented by dozens of residents across the state this July and August. These insects spend six months to five years as underwater nymphs before emerging for a brief adult life lasting only a few weeks or months. During this flying stage, they travel across vast distances, meaning their presence in any single neighborhood or farm is temporary as they "surf" pressure systems.
For the general public, the primary impact is a visible change in local ecosystems and a temporary decrease in biting insects. Residents will notice these swarms primarily in sunny areas near freshwater or open fields. Because the adult lifespan of these insects is short, the current high visibility of swarms is expected to subside as the migratory species move on or complete their life cycles. Experts suggest that those wishing to maintain these predator populations in their own gardens should avoid pesticides and provide fishless ponds, though the migratory swarms will naturally dissipate as they follow shifting weather patterns.