Happy National Moth Week! This week, citizen scientists around the country will turn on their flashlights, exterior lights, and specialized UV lights to observe this often overlooked and vilified group of organisms. Although moths are perceived as pests because their caterpillars damage cloth and tree foliage, they are one of the most diverse organisms on the planet and vary greatly in size, color, shape, ecology, and abundance.
Moths tend to be feeding specialists and rely on the presence of a host plant to feed on and use for cover during all their life stages. Some species can use a variety of plant species as hosts, but others are strictly specialized. Moth species relying on plant species from imperiled natural communities inevitably become critically endangered.
Here are some interesting details about two well-known moth species that can be observed in your yard:
Forest Tent Caterpillar Moth (Malacosoma disstria)
The Forest Tent Caterpillar Moth is one of the most vilified moth species in North America. They are known for their caterpillars’ tent-like silk mats and the damage they can do to the leaves of hardwood tree species such as alder, basswood, cherry, and oak. This moth species is prone to multi-year population explosions when localized defoliation can be dramatic, leaving trees draped in tangles of silken mats.
But guess what!
The Forest Tent Caterpillar Moth has a fascinating life history. Adult females of this species lay up to 300 eggs on a tree branch and cover them with a cement-like substance to protect them from drying out or freezing during the winter. In the spring, the eggs hatch, producing a “family” of caterpillars that feed, rest, and molt communally. Members of the group produce pheromone-covered strands of silk that the group follows together around their resident tree to feed and then use to return to their resting area. As each member of the leaf-loving family grows larger and nears pupation size, they begin to compete for food resources and start to forage more independently. Parents of teenagers can probably relate to this family dynamic.
Luna Moth (Actias luna)
The Luna Moth is one of the most recognized local species of moth due to its large size and brilliant lime green wings during adulthood. It has a markedly different life cycle from the Forest Tent Caterpillar Moth, as it spends only two weeks as an egg, less than two months as a lime green caterpillar, and completes the majority of its development in a cocoon during its nine months of pupation. Luna Moth host tree species are hardwoods, such as paper birch. Luna Moths make it their business to actively fend off predators with a couple of special skills. First, their brilliant green coloration makes them very visible when they perch under your deck light, but it allows them to camouflage among leaves very effectively both as caterpillars and as adults. If an adult Luna Moth is threatened, it will make a warning clicking noise with its mandibles. Then, it will regurgitate fowl-tasting fluids to deter the attack. Finally, studies have shown that the long hindwing tails of the Luna Moth can serve as a false sonar target to deflect attacks by bats.
We have much more to learn about moths to understand each species’ importance to ecological communities and conservation needs. Due to their diversity and typically nocturnal habits, moths can be evasive and difficult to research and monitor. National Moth Week is a time when anyone can take a few minutes to look in their yard or neighborhood, photograph moths, and share the data to help the learning continue. Visit the National Moth Week website to learn more about how you can contribute to this effort.