YORK COUNTY, Pa. (WHTM)– A helicopter will be flying over part of Central Pennsylvania performing aerial blackfly suppression Friday.

The York County Office of Emergency Management posted on Twitter that a white with blue and redd stripes helicopter with the tail number N660HA will be flying over the main stem of the Susquehanna River.

The helicopter will make its way south to York after a start at 8 a.m. in Northumberland County.

The reason for the suppression is to reduce the adult black fly population during the spring and summer, according to the Department of Environmental Protection (DEP). An estimated 1,700 miles of 48 rivers and streams in Pennsylvania are monitored for black flies.

Black flies are smaller than a house fly, measuring at about 1/8″ in length, and are often called gnats.

It is recommended by the DEP that people do not swat at these flies because they will quickly return and can fly into people’s eyes.

More information about black flies can be found online at DEP’s website.