Episode 334: Luna Moths

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Transcript 6/1/24:

Some flowers are not flowers at all and some magic is… well, who knows really? Welcome to The Nature of Phenology where we share the cycles and seasons of the outdoors. I’m your host, Hazel Stark.

At some point after the age where I had decided that fairies probably weren’t real, I saw one. My dad had taken me to a tennis court to teach me to play tennis on a late spring day. The pale green tennis ball bounced erratically off the cracked court that had fresh green grass growing from it. At one point, my dad stepped away for something, leaving me alone briefly among the new leaves and dappled sunshine. That’s when I saw it. A fluttering seafoam green creature dancing in the air above the court. It was bigger than any insect I had ever seen before, and smaller than most birds. It seemed bigger than a hummingbird but it was moving much too slowly. Of course it appeared when the adult disappeared—everyone knows that kids are much more likely to spot fairies than adults. As my dad approached the court again, the pale green creature fluttered away into the woods. Telling him about it, he said it must have been a luna moth. Classic adult explanation. But regardless of whether it was a luna moth or a fairy, now is the time of year to notice the fleeting adult stage of luna moths.

These large moths—their wingspans stretching 4.5-inches—are uniquely magical and stunning. Their wings are a pale—almost transparent—seafoam green, mostly surrounded by a burgundy-magenta border. Their back wings taper into a pair of curled long tails. A spot on each of the four wings is what gives them their name of luna moth as they are reminiscent of the moon. This family of moths, the Saturniidae, is so-named because of the eyespots with concentric rings like Saturn. In all species, their stunning coloration and patterning makes them indeed look out of this world. The U.S. Postal Service seems to agree, having made luna moths the first and only moth to appear on a stamp back in 1987. They are also on the cover of the 2005 edition of A Field Guide to Moths of Eastern North America and even showed up in ads for the medication Lunesta in 2007.

Luna moths live in the eastern US and into parts of southeastern Canada. In Maine, they are univoltine, meaning they have one generation of offspring annually. In Ohio and south, they can have two or three generations in a year. This moth cruises through its life cycle stages fairly quickly. They spend 10 days as eggs, 6-7 weeks as larvae, 2-3 weeks as pupae, and then just one week as a winged adult at about this time of year around here. The adults lack mouthparts as their only job is to reproduce in their one week of life at that stage.

With such short lives, these moths rely on important adaptations to help them avoid getting eaten at each stage. The caterpillars are a bright green that helps them camouflage with their broadleaved tree hosts in spring, like birches, alders, sumac, beeches, and maples. Caterpillars will also raise the front part of their body like a sphinx, making them perhaps less caterpillar-like to would-be predators. When really threatened, they will click their mandibles before regurgitating unappealing fluids in further attempts to repel a predator. As adults, their pale green coloration also helps them camouflage with their leafy environs and the spots on their wings, called eyespots, appear as eyes on a much larger creature to some predators, making them turn the other way. The long tails on these moths have an even more impressive purpose: their whirling motion through the air as they fly confuses the echolocation efforts of bats. A study found that 55% of interactions between luna moths and big brown bats left the bat unsuccessfully targeting the luna moth’s tail region, letting the moth get away.

So the next time you’re outside, you could be on the lookout for the fairy-like adult stage of a luna moth. Keep in mind that they are strongly attracted to light, especially the UV wavelengths of streetlights and other human-made outdoor lights, which may distract them from their goal of reproduction during their one week as adults—so keep your outdoor lights off as much as possible. Luna moths teach us that life is fleeting and there are many distractions along the way, so we should all focus on the important stuff and set aside whatever those distractions may be.

And on that note, this will be the last month of The Nature of Phenology so that Hazel and Joe, your co-writers of the past 7.5 years, can each focus on new and interesting ways to be in touch with the natural world. But you will always be able to easily access the transcripts and recordings of over 330 episodes and search by topic at thenatureofphenology.wordpress.com, which is also linked at archives.weru.org.  Thanks for listening and please join us next week for another dive into The Nature of Phenology.

References:

Barber, J. R., Leavell, B. C., Keener, A. L., Breinholt, J. W., Chadwell, B. A., McClure, C. J. W., Hill, G. M., & Kawahara, A. Y. (2015). Moth tails divert bat attack: Evolution of acoustic deflection. Proceedings of the National Academy of Sciences of the United States of America, 112(9), 2812–2816. https://doi.org/10.1073/pnas.1421926112

Hall, D. (2007, June). Luna moth – Actias luna (Linnaeus). Entnemdept.ufl.edu. https://entnemdept.ufl.edu/creatures/misc/moths/luna_moth.htm

Jess Moskowitz. (2022, July 31). Schoodic Signals: Luna Moth | Schoodic Institute. Schoodic Institute. https://schoodicinstitute.org/luna-moth/

National Geographic. (2015, July 16). Luna Moth. Animals. https://kids.nationalgeographic.com/animals/invertebrates/facts/luna-moth