Bad Astronomy

That’s One Impressive Moth-er Faker

White-lined sphinx moth
The riddle of the Sphinx moth. Click to lepidopterate.

Photo by Phil Plait.

Last week, Boulder was beset by apocalyptic rain and massive flooding. Where I live, a bit outside of the flood zone, streets were still impassable and basements were metamorphosing into bathtubs all around the neighborhood. My friend, the singer, siren, and chanteuse Marian Call had just arrived, having dodged a few inland lakes to visit. We sat in my kitchen, snacking on crackers and cheese and talking about the vagaries of life and weather.

I happened to look out the window, and saw a hummingbird flitting around our garden. The Sun had been trying to poke out from the clouds all day, and unlike their property owners some of the plants were quite happy with the recent weather.

I nodded toward it and told my wife and Marian it was out there. Mrs. BA looked out and said, “That’s not a hummingbird, it’s a moth. A hummingbird moth.”

Photo by Phil Plait

My reaction was some variation of “What?” or “You’re full of it!”, but either way the camera was called for. I ran to get it, and proceeded to take a few dozen shots of our visitor. Not many came out, but the one at the top of this post was the best. As you can see, it really is a moth.

Although I have some entomologist friends, I wanted to tackle this one myself. A bit of web searching and the answer popped up: We were visited by Hyles lineata, or a White-lined sphinx moth. Pictures on the web confirmed it; the pale salmon-colored band across the wings are a giveaway.

Note the pale pink banding that made identification easier.

Photo by Phil Plait

And the resemblance to a hummingbird is stunning. At first I thought it might be protective camouflage; a bird may be less likely to go after a hummingbird than something more obviously moth-like. Hummingbirds are fast, but they are also incredibly aggressive and mean—I’ve had them buzz me in a clear attempt to get me to move along. I weigh about 5000 times what a hummingbird does, so this takes some moxie. I imagine most birds would think twice about trying to snack on one.

But apparently this is a case of convergent evolution, where a series of environmental conditions happen to sculpt a similar morphology in an animal. Sphinx moths hover over flowers, wings beating madly—too fast to see—and use their long proboscis to drink flower nectar, much like hummingbirds. But the motion: Watching it in action was incredible. It would ziiiiip across the garden, poking into this plant or the next, just like a hummingbird. The acceleration was huge, and just before taking off it would dip just a bit to bite into the air more deeply—I’ve seen hummingbirds do that many times. The speed of their wings is phenomenal. The pictures you see here were taken at a pretty fast shutter speed (the top picture was 1/1600th of a second), just enough to freeze the rapid flapping (though focusing in rapid fire shutter mode is a different matter).

Check out the proboscis! It’s easily as long as the moth’s entire body.

Photo by Phil Plait

Of course, the physics of flight does constrain the engineering. If you have similar flying conditions, evolution’s easiest path is similar body construction.

I had never seen such a creature before, and was amazed all over again (as, I admit, I am most days) at how fascinating and wonderful the natural world is. Evolution uses many forces to craft its subjects, which can still lead to astonishing similarities; you can find spirals in galaxies and your coffee mug, and spheres from stars to cells. But that parsimony doesn’t reduce in any way the incredible diversity we find even when there may be a superficial resemblance between colorful individuals.

If there’s a life lesson in there, you’re welcome to find it. Science provides us with them every day, if you keep your eyes open.