Description: <p>Aerial surveys (mapping of damaged areas from a fixed-wing plane) provide a coarse overview of areas with moderate to high browntail moth (BTM) caterpillar populations. This survey takes place up to two times a year:</p><ul><li>Mid-June to July: defoliation by spring-feeding caterpillars is mapped.</li><li>Early-September: damage by late-summer-feeding caterpillars is mapped. This damage is often not heavy enough to warrant flights.</li></ul><p>Due to limited time and resources this survey usually underestimates the impacted area.</p><p>This data displays the towns where BTM defoliation has been observed with corresponding acreage.</p>