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SAN GABRIEL, Calif. () — Small black flies with a wicked bite are swarming parts of the San Gabriel Valley, and experts say their unusual early arrival is overwhelming residents from Azusa to Altadena.
Experts describe the insects as smaller than mosquitoes but far more aggressive. They aim for the eyes, and their bite is painful.
“They’re biting black flies, and so these are different than your regular housefly,” said Anais Diaz with the San Gabriel Valley Mosquito and Vector Control District.
Unlike common houseflies, black flies are drawn to human breath and the salty moisture around the eyes.
“Oh, that’s disgusting,” said North Hollywood resident Tamara Akins.
Diaz noted that while black flies can transmit river blindness, that risk does not apply locally.
“They are a vector for river blindness, which is a disease that you can transmit, but that’s not something that we see here. It’s mostly known in other parts of the world. Here, they’re mostly a nuisance,” Diaz said.
Still, the bites are unsettling.
“I don’t want anything to bite my eyes, even if they don’t transfer anything. That sounds really bad,” said Burbank resident Nina Boyce.
Vector control technicians are targeting black fly larvae in local riverbeds, where the flies thrive in fast-moving water.
“Our residents are really struggling right now. They’re overwhelmed with the amount of black flies,” Diaz said.
What stands out this season is the timing. Typically, black flies appear in May, with another surge in August, but their presence in late March is raising concerns.
“Right now, we’re experiencing very warm weather, and we’re seeing the river level a little bit higher than usual. So that’s creating new breeding sites that we have to address,” Diaz said.
Black flies can travel up to five miles and live for as long as two months. To avoid bites, experts recommend wearing DEET-based insect repellent and using a hat with a face net. Homeowners with water features are advised to turn them off for 24 hours once a week to disrupt potential breeding.
Visit sgvmosquito.org/black-flies for more information.
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