Moths, Butterflies and Ethical Questions

I read Patricia Grace's short story, "Butterflies"  years ago in college, and it has stayed with me all this time. In it, a little girl writes a story for school about how she killed all the butterflies. The teacher is appalled. Her grandfather observes later that the teacher must not grow her own cabbages.

I have grown my own cabbages (and collards and kale and other brassicas), and must admit to some inconsistency on the matter. I can't bring myself to kill the cabbage white butterflies. However, I have no problem flinging their looper caterpillars, which are just the baby butterflies after all, off my plants and to their doom under the bird feeder. To be fair, I grow only a tiny bit of my own food, for fun and to help the environment a little. If I had to rely more on my own cabbages to feed a grandchild, I would undoubtedly have a different attitude altogether. Ethics can be a matter of perspective.

I started pondering all this again the other day when I found this pretty mottled moth in the garden. 

It scurried about on the ground, then opened it's wings slightly so I could see it's underwings. Lovely!

iNaturalist Seek identified it as a large yellow underwing (Noctua pronuba), which Pacific Northwest Insects (Peterson, 2018) confirmed. The yellow underwings may be a deterrent to predators, although the moth is probably not actually toxic. A predator that had previously sampled a toxic or stinging yellow or orange insect might decide to avoid this one.

I noticed that Peterson listed the large yellow underwing as invasive, so I did some investigating. It is Eurasian (the cabbage white butterfly I mentioned earlier was also introduced from Eurasia). The moth was first recorded in North America in Nova Scotia, Canada, in 1979. Since then, it has spread across Canada and the United States, all the way to the Pacific Ocean and up to the Arctic. 

I was alive in 1979 (although small!); it just doesn't seem like that long ago! What a long way for a small creature to have spread! My amazement inspired some math. Halifax, Nova Scotia is 2761 miles from Seattle. The moths reached Washington state in 2000. That means they had to travel on average something like 131 miles a year. Sure, they can fly, but the adults only live for one or two months on average in captivity. I would imagine their lifespan in the wild is even shorter. There is only one adult generation a year. I wonder if they covered all that ground under their own power (amazing!) or if they hitchhiked rides with agricultural crops that were being transported.

To return to the idea of killing butterflies - due to their invasive status, some websites advised killing large yellow underwing moths on sight. My particular moth was long gone by the time I read that advice, but the idea still makes me a little squeamish. They are agricultural pests, especially in areas where winter wheat is grown. The larvae are cutworms; they live in the soil and eat the stems of plants. In the home garden, it seems they will eat just about anything, from brassicas to calendula to foxgloves. I've had trouble with cutworms in my beans and lettuce in previous years. Are these moths to blame? And while I don't want to kill an adult moth, I don't have much compunction about laying down a little diatomaceous earth around my bean seedlings to protect them. Well, I still have some mixed feelings, as I might kill non-target insects, but my beans are special - they are an heirloom variety given me by a friend, and I must protect them! Protecting food, protecting a treasured gift, protecting the life of an individual animal (it's not its fault that it's invasive) . . . I suppose the ethical dilemmas in the garden (as elsewhere) will continue.