One late June day, one of our staff members came across a beautiful luna moth near our towel exchange area. On closer examination, the moth didn’t appear to be doing well. Its color was fading and it was hardly moving. Our staff members tend to be passionate about caring for all living creatures, and after setting the moth safely on a rock, she came to ask us if there was anything she could do to help it.
The luna moth is one of the most stunning insects in the BWCA and all of North America, but seeing one is a rare event. If you’ve ever wondered about these beautiful creatures, how to see one, or – like our staff member – whether you can help one that’s struggling, this is the blog post for you.
The lifecycle of a luna moth
Unfortunately, there’s usually nothing you can do for a dying luna moth. That’s because they only live as moths for about a week. Their sole purpose during this time is to mate and lay eggs. The moths lack mouths and digestive systems, so there’s no way for them to stay alive longer.
Of course, like all moths, the luna doesn’t start life as a beautiful, winged creature, but as a caterpillar. Luna moth caterpillars are large and bright green like the moths they will become. They spend their days munching on leaves to store up energy for their metamorphosis and short life as a moth. One of their preferred trees is birch, which is common in this area. In the southern part of their range, they typically go for trees in the walnut family.
The caterpillars grow rapidly, shedding their skin about five times until they’re around 2.5 inches long. After about a month, they build a cocoon. In the southern US, the luna moth emerges three weeks later. However, in Minnesota and other northern areas, the luna spends winter in its cocoon and emerges in the spring.
Female luna moths produce pheromones to attract the males. The male moths have such sensitive antennae that they can sense the females from a mile away. After mating, the female lays hundreds of eggs on the undersides of leaves. These hatch into caterpillars later in the summer and the cycle continues.
What does a luna moth look like?
Luna moths are known for their bright green color and large size – their wingspan is often over four inches! The name “Luna” comes from the crescent shaped tails on their hind wings. Those long tails are more than decoration. The way they twist in flight prevents bats from finding the moths with echolocation. Each of the moth’s four wings also has a spot that looks like an eye to deter predators.
Female luna moths tend to be a bit bigger than males and are a darker shade of green. Their antennae are also thinner than the males’.
Where do luna moths live?
Luna moths live in much of the eastern half of the US and southern Canada. They like forested areas with their preferred species of deciduous trees, such as birch, butternut, walnut, or hickory.
When to see luna moths
Because their lifespan is so short, there’s only a brief window for seeing luna moths. At Bearskin, as with other places in the northern US, May and June are the best months to spot one. Farther south, luna moths can go through multiple generations per year and be seen more frequently.
Another reason the moths are hard to see is that they’re nocturnal. During the day, lunas hang beneath leaves with their wings folded together. They blend in with the leaves and are almost impossible to spot during this time. That’s why if you do see one in daylight, it’s often dead or dying like the one Meg found. You might also see one if its hiding spot is disturbed and it’s looking for a new leaf.
Are Luna Moths endangered?
It’s not often that you get to see a live luna moth, so you might wonder if they’re very rare. It’s true that the population has declined due to factors like habitat loss, pesticides, artificial lighting, and predation from invasive species. However, luna moths are not considered a threatened species in most of North America and are actually a lot more common than you might think. It’s just rare to see them due to their nocturnal schedule and short lifespan.
Come to Bearskin in May or June and you may be lucky enough to spot one of these magnificent moths.
