OSAKA - At the Osaka-Kansai Expo site, a large outbreak of insects has raised concern, with the Expo Association announcing on June 2nd that the source is likely the water features fed by seawater located within the venue.
The insect in question is the non-biting midge Chironomus yoshimatsui, commonly mistaken for a mosquito. Swarms have been seen particularly in the southern part of the venue, including atop circular viewing platforms, causing a nuisance to visitors and staff. While the association had earlier suspected stagnant puddles as a possible breeding ground, Kansai TV had pointed to other potential sources.
On May 21st, researcher Yamamoto Naoshi, an expert on midges, investigated the southern Water Plaza area with a net and discovered a midge breeding site. "That seems to be the nest. If you scrape it with a net, you'll see red larvae come out," he explained, clarifying they were larvae rather than eggs.
The Expo Association now believes with near certainty that the midges are breeding in the "Water Plaza" and the connected "Sea of Connection" areas in the southern section of the venue.
Jun Takashina, deputy secretary-general of the Expo Association, stated, "We cannot eliminate the midges immediately, but we want to swiftly identify appropriate solutions and implement countermeasures."
The association held an emergency task force meeting on June 2nd and plans to proceed with discussions on insect control measures.
The species Chironomus yoshimatsui is typically found in brackish or freshwater habitats, especially those with slow-moving or stagnant water. Their lifecycle involves four stages: egg, larva, pupa, and adult. Eggs are laid in gelatinous masses on the surface of water, and the hatched larvae quickly sink and burrow into sediment, where they create small tubes of detritus and organic matter. In their larval form, they are sensitive to environmental changes and can serve as bioindicators for water quality. Once mature, they pupate and emerge as adults in large synchronized swarms, often during the warmer months. Adult midges of this species do not feed, as their primary role is reproduction. They typically live only a few days, forming large clouds that can be visually overwhelming and cause discomfort for people due to their sheer numbers, especially when they gather near artificial lights or on white surfaces.
Related: Swarm of Insects Causes Panic at Osaka Expo's Giant Ring
Source: KTV NEWS
