If you've driven along Francis Parkman Drive recently you may have seen a sizable forest area clearcut by the city to remove dead trees, some of which killed by an insect that feeds by sucking sap from hemlocks. The removed trees were between the Francis Parkman Drive and Prince Street, including a hemlock grove and individual trees that were dead or failing, said Margaret Dyson, Director of Historic Parks for the Boston Parks and Recreation Department. The area looks to be several hundred square feet and is visible from Francis Parkman Drive. The culprit was the hemlock woolly adelgid, which is native to east Asia, where's it not a problem because natural predators keep it in check. But on America's east coast it goes unchecked.