A moth floats on the water in a swimming pool

Mystery of the Moth

A giant moth landed in our swimming pool.

It couldn’t swim, but not for lack of trying. The moth pushed and pulled its wings, as though doing the breaststroke. Bert pulled the creature from the water.  The soaked moth flapped its wings, turning quarter circles on the pool deck.

But the hot concrete was scorching my bare feet. I thought the insect might fry before it had a chance to dry out and fly.

So, I carried the moth to a shaded location—a countertop in our little barbecue hut. After standing mostly motionless for an hour or so, the moth hopped (or did it fall?) to a second counter ten inches below.

That’s when I realized the moth was a female. She had laid two tiny (1/8th inch) eggs on the first counter. A few hours later, she budged again, and we found four more eggs.

The surprise pool guest was a silk moth: Antheraea polyphemus, a big (6” wingspan) beautiful moth known for its large, owl-like eyespots.

When the moth was in the pool, her eyespots were blue. When we fished her out with a net, they looked white. Her spots were blue and yellow on the pool toy we used to nudge her from the net.

Moth on a pool toy, showing its transparent eyespots.
Colors visible through the transparent eyespots of Antheraea polyphemus

The eyespots turned brown on the countertop. But they weren’t changing color; instead, the spots are transparent like little windows, a characteristic unique to Antheraea polyphemus.

The moth stayed on the counter all afternoon and evening. She was still there—alive but nearly motionless—the next morning. If you’re feeling bad that the creature’s swim shortened her life, that’s likely—but not by much. These moths live just five days after exiting their cocoons. The moth’s sole goal during her brief Earthly stay is to mate and lay eggs.

Here’s a video with clips taken over some 28 hours.

I’m left pondering several mysteries. First, the eggs. She should have laid between 100 and 200 eggs on leafy branches that would provide food to her caterpillar hatchlings. She laid six eggs on our counter. Had she done her reproductive duty on some tree before her dip in the pool?

Antheraea polyphemus. Underside shows her ovipositor, through which she deposits eggs.
Underside view shows her ovipositor, through which she deposits eggs.

The second mystery also pertains to the eggs. A cement countertop is about the worst place for her to lay them, as her hatchlings will have no access to food. So, thinking I might relocate the eventual caterpillars to an oak branch, I put the first two eggs in a small plastic container. I left the lidless container on the countertop. Later, adding the four additional eggs, I was stunned to see an empty container. I found one egg about a foot away, but the second was… gone.

Small plastic container with moth eggs removed from concrete counter
Moth eggs removed from the concrete counter.

So, what creature found the eggs, took them, and dropped one on the counter?

The biggest mystery is of course, why she was in the pool. Bert noticed her at about 10 am. It seems unlikely she landed in the water during the prior night. She’s so big, I think we would have noticed earlier in the morning, and I doubt she could have survived many hours in the water. The lady is nocturnal… she’s supposed to lay her eggs in the late afternoon or evening after leaving her cocoon. So what the heck was she doing out and about in morning daylight? And what on Earth happened to make her land in the water?

Theories, anyone?

2 thoughts on “Mystery of the Moth”

  1. I don’t know the answers, Carol, but we would occasionally have these beautiful butterflies (or moths) in Michigan. When they were ready to expire, they just seemed to lose strength. They would land or drift wherever they happened to be. Yours happened to be near the pool. I think the eggs were just the last ones she had in her tube. She didn’t have the strength to fly to a branch maybe. They would be tasty morsels for lots of things: birds, ants, maybe even a possum? If you still have her after she expires, could you mount her to use in an illustration or another children’s book? How lucky she landed in your pool.

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