Photo by Jeff Tome This Laurel Sphinx caterpillar mostly eats ash trees. This moth may disappear with the ash trees as they decline with the introduction of the Emerald Ash Borer.

Editor’s Note: This column originally ran in 2019.

Where are your blind spots? In a car, these are the spots that you cannot see when turning or backing up. Fancy cameras and screens are being used to help drivers see their blind spots. But no camera can cure a mental blind spot, and the effects of that are everywhere. We often don’t see the things that we haven’t trained our brains to see.

There is a famous video of a group of people watching dancers onstage. A man walks through them in a bear costume, but no one notices because they are so focused on the dancers. The human mind is capable of such focus that it is possible to not see something really obvious.

One of those disconcerting moments happened to me one past summer as I talked to Cornell entomologist Jason Dombroskie, who was collecting moths at Audubon as part of a research project to identify the moths of New York.

My knowledge of moths is limited to identifying only a couple dozen species of the hundreds that are out there. Some are easy to identify, most are put into my mental “small gray moth” category and ignored.

I was rather proud of myself when I could identify some of the moths that he had found, since the odds of him finding one of the few I know were slim. One of these was the Waved Sphinx moth. These gray moths are masters of camouflage, but have distinctive wavy black lines and a white eye-shaped dot on the wing that make it one that I recognize.

“This moth is in danger of going extinct” Dombroskie said. This news came as a complete shock to me, but it shouldn’t have. The answer to why was lurking in my blind spot, hiding in plain sight amongst all the facts that I knew, but hadn’t put together yet.

Waved Sphinx moth caterpillars mostly eat Ash trees, though there is evidence that they will eat oak and privet as well. Ash trees are slowly but surely disappearing from the region with the spread of a tiny green insect called the Emerald Ash Borer (EAB). This insect bores into the ash tree and kills it within a year or so. As the main food source for the caterpillar dwindles, the moth may disappear as well.

According to the journal “Biological Invasions”, there are forty-three species that depend on ash trees and may disappear. Some are moths, like the Waved Sphinx, and others are lesser known insects that feed on the leaves, seeds, and bark of ash trees. These species only feed on ash and not other plants, similar to how Monarch caterpillars only eat milkweed.

The study noted 282 species that use ash trees. Of these, 208 are at a low risk for going extinct. Thirteen are at a medium risk and 17 are at a high-moderate risk of extinction that join into the 44 at high risk.

For me, that was a pretty big blind spot. At Audubon, we treated the ash trees in the Ted Grisez Arboretum to keep the Emerald Ash Borers from killing them. My thoughts never went beyond the tragic loss of a tree species to wonder at the loss of other species that could disappear with them.

If the disappearance of ash trees from the landscape could wipe out other species, did that happen in the past? A quick search revealed that the chestnut blight of the twentieth century took out at least five species of moth and a weevil, as well as billions of American Chestnut trees. While scientists are working on helping the trees make a comeback, the insects that disappeared with the majority of the chestnuts are gone for good.

When an insect goes extinct when the plant it depends on disappears, it is called co-extinction. While the American Chestnut did not go extinct, it became scarce enough that many of the insects that depended on it disappeared.

This was my blind spot. As I figure out how to get dead ash trees safely down, or buy ash firewood that is popping up in people’s yards, I never thought to look at the ripple effect of a tree’s disappearance. It affects insects and, through them, other animals whose lives revolve around a tree threatened by an Asian insect brought here by accident.

It’s a pretty big blind spot, and one that I was glad to have pointed out. One of the hardest things to do is think of all the consequences of human actions. It never occurred to me that I would have to mourn the loss of moths that disappeared with the ash, or that there were species I would never see because of the disappearance of the American Chestnut. It puts everything in a different light and, even if there is little I can do to stop it, I can still stop and pay attention to the loss of a species.

They are looking for ash trees that are resistant to EAB. They are popping up here and there. With luck, in ten years I will not be writing a eulogy for the insects that died with their only food source.