The BioGeek Memoirs: Miller Moth

Last night a miller moth got into the house. The cats staked it out and Hannah kept trilling for me to come help her get it. The poor moth, trapped in my house in an environment that was definitely not safe, clung to the wall up near the ceiling.

These moths are small: about an inch across and they will leave a dusty powder behind if you touch them. This powder, reminiscent of the powder on people working in flour mills, is the source of the moth’s common name.

Later in the evening, after I had turned out lights in the house and was reading in bed, the moth, attracted by my reading light, arrived upstairs to bat and fly around my light. Chaos erupted as cats launched themselves towards the moth, and I grabbed the lamp. Mateo dove down the wall behind the bedside table, chasing the moth while Hannah tried to cut it off from the other side. Sigh. It was another long night…

This year there are an awful lot of moths on the move. Look at what showed up on my Facebook feed!

That’s right. As the cats and I know well, these moths are creatures of the night. I see them snacking on flowers that attract moths (lilacs, I’m talking to you!!) and bopping around lights during the night hours. Why these moths, creatures that hide from light all day, are attracted to sources of light at night, is a mystery to me, but there you are. There are several theories about why this happens, which you can read about here if you’d like.

Miller moths are annual visitors to my part of Colorado as they migrate westward towards the cooler foothills of the Rocky Mountains for the summer. In their caterpillar stage of life these moths existed as army cutworms, wreaking havoc on crops and grasses in fields on the Great Plains to the east. Once they emerge from their cocoons, the adults take to wing and head west in a great migration that lasts for weeks every May-June. Why are they doing this? There is a lot of speculation, but mostly it is thought that they are looking for better food and cooler conditions to survive the hot summer.

I try to keep a good attitude about the moths at this time of year. These moths are nocturnal and hunt for hiding places during the day where they are safe; too often they crawl into the cracks at the edges of the doors and windows and if you open one, the moth will take flight, end up in the house, and begin frantically searching for another hiding spot. Opening the garage door sets off a flurry of moths. I’m not going to lie; it can be really spooky when an unawares homeowner opens the front door to an erupting cloud of moths suddenly taking flight and batting against their face and hair. In my case it is worse because I have a storm door outside of my front door, and when I open the door, the moths have no place to fly except into my house. <Cue the cat excitement!!> How do those moths squeeze past the storm door to get inside the gap? They are experts at squeezing through tiny openings! Seriously, it has been so bad this year that this also showed up in my Facebook feed:

You are supposed to gently trap them and return them to the outside world where they belong. Here is the link to the article.

Can you hear Mateo wailing why??? He thinks that these moths are the best cat toys ever, and this is what Hannah looked like the first time she saw a moth on the wall:

Hannah: what is that??!

Well, the reason why they should go back outside is because they are important to the ecosystem. They are significant pollinators of flowers like the lilacs I mentioned above and other plants with strongly scented (and lightly colored) flowers. They are also important sources of food for birds like swallows; right now, there are furballs of swallows dipping and darting through some intersections and dodging cars as they snatch moths from the air. It is so bad it can be concerning when you approach the intersection; a swallow hit a car next to me while I was waiting at a light yesterday. Clearly, there are miller moths at these intersections and the birds are dive-bombing the cars as they hunt the moths. The reasons aren’t clear why the feeding is so good at some intersections, but as with all things miller moth, there you are. It must have to do with the lights, the lines between the poles, the swirling air, nearby fields, whatever. Just another magical phenomenon associated with the migration.

There is one last thing that I think of when the miller moths arrive. It is time for the kids to graduate! Year after year, graduation after graduation, I shook the hiding miller moths from my robes, carefully arranged my masters hood around my shoulders, and marched with my students as they left me and moved on with their lives.

The best migration ever!