The San Gabriel Valley is seeing an unusual increase in eye-biting black flies
Residents of the San Gabriel Valley are dealing with an alarming increase in black flies, a painful little insect known to bite the eyes and necks of people and pets.
The San Gabriel Valley Mosquito and Vector Control District issued an alert this week advising residents of a spike in black fly activity in mountain communities including Altadena, Azusa, Bradbury, Duarte, Glendora, Monrovia, San Dimas and Sierra Madre. Flies breed rapidly in running water, where females will lay 200 to 500 fertilized eggs at a time.
“Black flies are currently very active in the San Gabriel Valley, and many residents are feeling frustrated,” the county said in a statement. “Right now, the population is increasing due to favorable conditions, and black flies can travel five kilometers from where they come from, which is why they are visible throughout the community.”
The county is treating the river’s spawning grounds to reduce the population, but warns that this could take several weeks to take effect.
In the meantime, residents are advised to take protective measures such as wearing long pants and long sleeves and using a protective net over one’s face. People should also consider using a repellent containing DEET on exposed skin and turning off personal water features such as fountains for 24 hours once a week, according to the district.
The bugs, measuring two to three millimeters, are so small that they can be hard to see. However, their bite can pack a painful punch.
Azusa resident Constance Yu described the persistent bedbugs as “little but little demons,” while dismissing critics during an interview with CBS News this week.
Although flies cause discomfort, they are not known to transmit disease in LA County, according to the vector control district.
Black fly spikes are often caused by the systematic release of water from upstream dams, which is necessary for water management in the area but also creates favorable conditions for the insects to breed.
The county monitors and sprays pesticides in breeding areas — including local rivers, streams and places like Morris Dam — and sets traps in mountain communities to track population size and minimize impacts to residents.
This time last year, the surveillance traps had single digit black flies. Now they catch more than 500 flies at a time, district spokesperson Anais Medina Diaz told LAist.
Diaz also said it’s normal to see so much flight activity this time of year, noting that the uptick is likely linked to the recent heat wave. Southern California is enjoying its hottest March on record, leading to snow drifts from the mountains.
“We’re dealing with them now because of the warm temperatures we’ve had,” said Diaz. “And of course, all the water falls into the river, we have unusually high flows for this time of year.”
Black flies aren’t the only pesky creatures that operate during unseasonably warm weather.
The Southland has also seen more rattlesnakes, with two recent deaths, as the early heat draws more rattlesnakes to mountain passes. Sweltering sea temperatures have been linked to great white shark sightings at Newport Beach which led to a temporary beach closure on Thursday.
