A mosquito breed known for carrying yellow fever and other diseases has been spotted in portions of the San Joaquin Valley. Last week, the San Joaquin County Mosquito and Vector Control District said high numbers of Aedes aegypti mosquitoes have shown up in traps around South Stockton, Manteca, Escalon and Ripon. The mosquitoes have also popped up in Butte and Glenn counties this summer. Like the majority of other mosquitoes that live here, Aedes aegypti are not native to the state. They’re also relatively new to California, having first shown up in traps in 2011, according to the state’s Department of Public Health.