Biology and impact of Nepytia janetae (Lepidoptera: Geometridae) in southwestern high elevation forests

Janet’s looper is an emerging pest that historically has caused no noticeable damage. Recent outbreaks in three mountain ranges in southern Arizona and New Mexico have resulted in 40-100% mortality to Engelmann spruce and corkbark fir. Our observations on the life history show that Janet's looper is univoltine with synchronous egg eclosion but asynchronous pupal ecdysis. It is a winter-feeding insect that scores the needle surface as small larvae and is a sloppy chewer as large larvae, causing complete defoliation of host trees. Outbreaks develop rapidly, last 2-3 years, and collapse due to starvation, parasites, and disease. Bark beetle populations may develop in defoliated trees, and the combined effects of defoliation and bark beetle attacks caused the extreme levels of mortality observed in the Pinaleño Mountains. Host specificity is unclear, Arizona populations fed equally on Engelmann spruce and corkbark fir but refused Douglas-fir and southwestern white pine, in the field and in rearing cages, while the New Mexico population fed indiscriminately on all coniferous species present, including Engelmann spruce, corkbark fir, Douglas-fir, white fir, southwestern white pine, and ponderosa pine. The unprecedented nature of the outbreaks by an insect known previously only from its taxonomic description indicates that this species may be responding to altered environmental conditions, and the winter-feeding life history, temperatures during outbreaks, and the high elevation situations indicate that it is responding to warmer climate.