Tuesday, July 2, 2019

Hummingbird Moths, A Primer

Hummingbird Moth One afternoon last summer, my partner Rick called me out onto our deck to see a tiny hummingbird. Not just tiny, but the tiniest hummingbird he had ever seen. My curiosity piqued, I walked out and there it was – hovering in front of the bee balm, sipping nectar and beating its wings at an impossible rate. It was a rich rust color and about an inch and a half long. By comparison, the smallest ruby-throated hummingbirds are twice that length. This was truly the most diminutive hummingbird imaginable.

Or was it?

When I first spotted it, I was certain it was not a hummingbird. It didn’t seem possible that in all my years of birdwatching, I had never seen this particular species, nor even heard of it. A one-and-a-half-inch-bird, after all, would be something of note. The kind of thing people spend their lives hoping to see, crowds gathering as word of a sighting spread. But the longer I watched it, the less sure I felt. It moved exactly like a hummingbird – hovering, sipping, furiously flapping. I wondered if we had stumbled upon a wayward bird far afield from its home somewhere in the tropics.

We had not. It was a moth.

More specifically, it was a hummingbird moth – a tiny trickster that sounds, acts, and looks much like its namesake. There are several species that fall into this family, known as the Sphingidae or sphinx. The most common in our area, and the one zipping around my garden, is the hummingbird clearwing moth (Hemaris thysbe). Another common species, the snowberry clearwing (Hemaris diffinis), tends to be more abundant in the West. (There is also a genus, Macroglossum, found in North Africa, Asia, and Europe. It is known as the hummingbird hawkmoth and has an epic migration, some of them flying from the Mediterranean and even North Africa to the United Kingdom.)

After the sighting in my garden, I did an internet search on “tiny hummingbird” and discovered that I was not the first person to be fooled. Looking at photos of the insect, I could clearly see it was just that – an insect and not a bird. What looks like a sliver of a beak is actually a proboscis that the moth plunges deep into blossoms for nectar. When not in use, it retracts into a coiled position. It also sports a pair of unbird-like antennae. Details that were hard to see as it flitted about the bee balm in the middle of a sun-drenched day.

Even in caterpillar form, the Hemaris thysbe is easy to mistake for something else. It’s a beautiful spring green, with spots along its sides and a horn on its rear end. In other words, it is almost identical to the tomato hornworm. “All caterpillars in the family Sphingidae have a horn at the rear end,” said biologist Beatriz Moisset, who writes about pollinators for the U.S. Forest Service. “They look similar to tomato hornworms, but feed on different plants, mostly honeysuckles, viburnums, snowberries, and a few others.”

I was relieved to learn this, as I have had an infestation of tomato hornworms two summers in a row and didn’t want to regret the fates they met at my hands. Turns out those garden decimators transform into five-spotted moths and not into the bird look-alikes checking out my bee balm.

Adult hummingbird moths first emerge in spring, but are most active in summer, when flowers such as bee balm and phlox are in bloom. Females lay eggs on the underside of leaves that the larvae eat, including honeysuckle and dogbane. When the caterpillars are full grown they drop to the ground, where they will spend the winter in cocoons. Leaf litter is essential to their survival.

“An immaculate lawn is a death sentence for any pupa laying there. So, if you can reduce the area you rake in the fall, you may be saving some of these beauties” said Moisset. I’ve never been particularly zealous about raking my lawn and now I am even less so.

The sighting last summer proved to be a singular event, but I am hopeful more will follow this year. The next time a hummingbird moth shows up in my garden, I won’t be fooled, but I will be delighted.

Carolyn Lorié lives in Post Mills. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation.

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The Adirondack Almanack publishes occasional guest essays from Adirondack residents, visitors, and those with a biding interest in the Adirondack Park.

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5 Responses

  1. Boreas says:

    Great article! My laissez-faire lawn philosophy seems to be working because I always have these wee beasts in my summer flowers. They are certainly fun to watch. They even dart off for a few minutes then come back to the same flowers just like hummers do. One thing I have NOT noted is any type of interaction with my very territorial male hummers. Seems odd. Very interesting critters!!

  2. Suzanne says:

    The hummingbirds perhaps don’t feel territorial because they’re birds, and the moths are, well, moths, so there is little reason for them to interact. My hummers are feisty and fight amongst themselves. Both they and the hawk moths love Salvia, so planting a big patch, if you haven’t already done so, will bring them, and also bumble bees, to your garden. How fortunate we are to live with these lovely creatures.

    • Boreas says:

      Suzanne,

      Most territorial displays and concerns regarding Male hummers is over food sources. My feeling was that the males would be aggravated by anything interfering with its food sources. I get buzzed by males every time I go near my feeders. Perhaps they simply aren’t as aggressive around flowers. If these moths visited hummer feeders I think we would see more friction.

  3. Mike says:

    Just saw this bird-bug in our yard for the 1st time EVER! I had no idea what it was. Fascinating little creature. I managed to get a decent video and picture.

    • Boreas says:

      Mike,

      Yes, they are fascinating! I have 3 this year (a record for my yard) and they are very approachable. They may fly away for 10-20 seconds, but typically come right back. Had one land on my hat for a few seconds when I was taking a video.

      I would be interested to find out if there was an evolutionary advantage to mimicking a hummingbird (and what that would be), or if it is simply a case of parallel evolution – form following function.

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