Taken one at a time, the mosquito is relatively benign. Roving swarms can make visitors miserable though. They breed in standing water which means wherever snow melts and, for several months a year, Yosemite has lots of melting snow. Typically, mosqitoes are common at 4,000 feet in the late Spring. By mid-summer, they can be found at up to 10,000 feet.
What can you do about these pesky critters? We suggest long pants and long-sleeve shirts and repellent. Mosquito-netting also can come in handy. If backpacking, locate your camp away from standing water and where it might catch a breeze.