A Boston woman pleaded guilty to armed robbery of U.S. Postal Service carriers in Mattapan and Hyde Park.

Myesha Lewis, 22, pleaded guilty Wednesday in federal court in Boston to multiple charges related to her role in the Nov. 29, 2022, Mattapan robbery and the Dec. 16, 2022, Hyde Park robbery. According to court documents, she was the getaway driver and criminal companion to co-conspirator Kenneth Demosthene, who was sentenced to three years in prison a week ago.

Prosecutors say that Lewis and Demosthene robbed two letter carriers of their “Arrow” keys, which unlock the blue U.S.P.S. letter drop boxes that line the city. The boxes have been a longtime target of thieves who either “fish” for letters inside with tools or, more expediently, rob letter carriers of their master keys. The object is to score checks in the envelopes.

The Postal Inspection Service noted an uptick between 2016 and 2021 in “mailbox fishing” in Massachusetts. The U.S.P.S. responded with boxes hardened against such fishing, but that led to a spike in robberies of letter carriers.

There have been “at least” 23 assaults on letter carriers in Boston and surrounding communities since July 2022, according to a Wednesday statement from the U.S. Attorney’s office. Of these, 15 robbers were armed with a knife, gun or both.

Court records do not indicate that Lewis and Demosthene were armed in their earlier robbery in Mattapan but that the second robbery was made at knife point.

Kenneth Demosthene, 24, as seen from stills of area surveillance footage around the time he robbed a mail carrier the afternoon of Nov. 29, 2022 in Mattapan. (Courtesy / U.S. District Court)