Luna Moth from the Chutes

2018 July 7

On June 20, 2018, we were on our way across Ontario[1] and stopped at Chutes Provincial Park to camp for the night. The park was nowhere near full (the ranger that we met said that the park didn’t normally get busy until after Canada Day on July 1), and so we had a nice secluded campsite within listening distance of the rapids that the park is named after[2].

Anyway, while we were setting up the tents, I happened to look down and see an odd-colored leaf next to my foot. And then realized it was no leaf.


It was a recently-deceased Luna Moth, Actias luna.


I’ve seen these around home from time to time over the years[3], and posted a picture once before, but the previous posting was a single cellphone picture that someone else took. Since the most cooperative insects for photography are dead ones, this was obviously a golden opportunity to get more pictures of what is arguably one of the most attractive moths in North America.


Being recently dead[4], it was still flexible enough that I could get the wings spread out flat.


The body was uniformly white and fuzzy.


A notable feature of their wings is the long tails, which would seem to be not good for much. They don’t contribute anything useful to the moth’s aerodynamics, and they can evidently fly just fine if the tails are removed. But, just a couple of days ago, I happened to see this news item about a study of the function of those tails. It turns out that they function as sonar jammers/decoys. They actually tested bats pursuing moths, and found that the bats were frequently tricked into thinking that the sonar return from the tail was from the moth’s body, and the moth would escape when the bat tried to snatch the tail. Luna moths had about a 70% chance of escaping the bats when the tails were intact, but only about a 34% chance if the tails had been removed. And, when they did tests with Polyphemus moths (which don’t normally have the tails), they found that attaching artificial wing tails just about doubled their odds of escape. The slight twist to the tails is believed to increase the sonar return, all the better to deceive the bats.

[1] Sam’s comment: “Canada is a lot like home, only with French subtitles.”

[2] The Chutes are a series of pretty severe rapids and short waterfalls. Back in the logging days, logs were floated down the river to the mill, and evidently it was pretty impressive to see them go through the chutes.


[3] Back in the days before digital cameras, I found a Luna moth on the screen for our bathroom window, and photographed it with my old film camera. Unfortunately, none of the pictures came out all that great. And then, about ten years ago, I happened to notice a set of Luna moth wings, along with a set of Cecropia moth wings, underneath some bats roosting around the door of the building that I work in. The bats had obviously brought the moths home to eat at leisure, and then dropped the wings.

[4] Like the other giant silk moths, they don’t eat as adults. They mate, lay their eggs, and then they die of old age and starvation within a week or so, assuming that nothing eats them first. Which means that they are likely to still have nearly pristine wings when they die.

One Response
  1. August 1, 2018

    I love the bit about the sonar decoys. It’s a good thing they don’t drop chaff, otherwise the ground would be littered with moth wing bits. Thanks for sharing!

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