Mainers are being warned to check their vehicles for browntail moth caterpillars seeking to hitch a ride this summer. Browntail moth caterpillars, which cause an uncomfortable, itchy rash reaction when touched, can become “expert hitchhikers,” at this time of year into late June, according to the Maine Department of Agriculture, Conservation and Forestry. If browntail moth caterpillars seeking to catch a ride on vehicles, ATV’s, boats and other recreational equipment are not eliminated, they can spread an outbreak of the irritating critters to other parts of the state.