Erannis tiliaria

Periodically, the population of the linden looper rises to the extent that deciduous trees such as linden, apple, birch, elm, hickory, maple, and oak are defoliated. This native insect is found in the northern half of the United States and parts of Canada. Their populations can also overlap with the cankerworms. Adult female moths lay their eggs in clusters of 3-4 under loose bark on the trunk and larger limbs of its hosts. (One female was dissected and her abdomen contained 583 eggs (average of 300 eggs per female; Schoene, 1916).) Eggs are pale yellow in color when first laid, but turn to lead-gray prior to hatch. Eggs hatch at bud break (late-April to mid-May) and the caterpillars spend approximately one month feeding on host plant foliage. Early instar caterpillars can spin a silken thread and disperse using the wind by ballooning. These geometrid caterpillars have 2 pairs of prolegs and move in an inch-worm motion. Early instar larvae feed during the day, and older caterpillars may feed overnight. Fully grown caterpillars can be up to 3.5 cm in length, with yellow sides and a band along the back which varies in color between individuals. The back may possess up to 10 dark pinstripes, with yellow or brown in between. The underside of the caterpillar is chalk-colored. The head capsule of the caterpillar is usually a pale orange-brown. The spiracles (breathing openings; seen along the yellow stripes on the sides) are ringed in black. 4-6 instars are reported for the caterpillar stage, with 4 being reported as typical in Massachusetts populations. Eventually, caterpillars crawl to the ground beneath their host where they burrow 2-6 inches into the soil. This is where pupation occurs. Caterpillars finish feeding by mid-June and are typically in the soil by July. The greatest numbers of pupae are reported from the soil beneath leaf litter beneath trees and shrubs. From October to December, typically after the first frost, the adult moths emerge and wingless females lay their eggs. Female moths have two rows of large black spots along their back and are approximately 13 mm in length. Like other wingless female moths, they crawl up their host plants to lay their eggs. Males fly at night, and are sometimes attracted to outdoor lights in large numbers, and may be especially noticeable in vehicle headlights. Adult moths are called linden looper moths - however some literature refers to them also as "winter moth". In Massachusetts, however, that common name refers to Operopthera brumata. Caterpillars of the linden looper may also be called "lime tree looper" by some, however that common name may refer to another non-native species (Hybernia defoliaria) found in Europe. Linden loopers are a "boom and bust" species. In most years, their populations are present in low numbers. Occasionally, population outbreaks lead to localized defoliation. Johnson and Lyon (1991) and Wagner et. al (2001) note that the overwintering life stage is the egg in this species, however Wagner (2005) states that the pupa overwinters in an earthen cell - this may refer to the behavior of this insect in the part of its range found in Canada, where most of the adult emergence is reported in the spring (Britton, 1932). 

Note: A 1965 Master's thesis by Chih-Chung Liu, "Preliminary study of the life history and behavior of the linden looper, Erannis tiliaria (Harr.) (Lepidoptera: Geometridae)." is a great resource for more information about historical outbreaks of this native species, as well as its biology and natural enemies, in Massachusetts.