UNDATED (KDAL) - Over the last several years the forest tent caterpillar populations have been on the rise in northern sections of Minnesota. The data suggested that the so-called "army worms" were building toward a peak in 2014 or 2015. But, so far this year the hatch is more sporadic according to DNR Forest Health Specialist Mike Albers. Last year the acres of defoliated trees from the caterpillars reached about 1.1 million, much lower than the nearly 8 million acres defoliated during the last major outbreak on 2001 and 2002. The cold weather and heavy snowfall this winter may have delayed the egg hatch, but Albers says the native forest tent caterpillar egg masses can easily survive 40 below zero temperatures.