Double Take: Why Hummingbird Moths Look and Act Just Like Hummingbirds

A tiny creature flits from plant to plant under the summer sun. It moves fast, then stops abruptly at a flower’s lip; it sips, then darts aside, its minute body humming red and green.

It flies like a hummingbird, feeds like a hummingbird, but it isn’t a bird at all: It's a moth. 

That’s right—it’s a hummingbird moth, a subset of large, stout moths in the hawkmoth family (Sphingidae). Also called sphinx moths, there are about 1,400 hawkmoth species worldwide, including 115 in North America, living in meadows, woodlands and gardens. Both names reference behavioral traits: These moths fly strong and steady like hawks. And as larvae, when threatened, they raise the fronts of their bodies like the Egyptian Sphinx. 

Most hawkmoths hover and eat nectar—but it’s the small minority that feed in daytime that are known as hummingbird moths. These include North America’s four “clearwing” species: the hummingbird clearwing (the most common), and the snowberry, slender, and Rocky Mountain clearwings. Their transparent wings, unusual in moths, may help obscure them from prey. Other hawkmoths include the white-lined sphinx, whose wings flash pink, and the five-spotted sphinx, final form of the infamous tomato hornworm. 

How Hummingbirds and Hummingbird Moths Are Alike 

The animals’ likeness is not just superficial. Like their namesake, hummingbird moths can hover by beating their wings in a rapid figure-eight, up to 70 times per second (some hummingbirds can manage 80). Both can fly backward. And to reach deep inside flowers, both have unusually long, strawlike mouthparts: Hummingbirds have lengthy beaks and extendable tongues (wrapped around the insides of their skulls), while hummingbird moths have proboscises twice as long as their bodies (that coil beneath their chins). Both are drawn to brightly colored, tubular, nectar-rich flowers. And both have high metabolic rates. No wonder: That high-energy flight style needs a lot of sugar to sustain it. 

Despite all this, the hummingbird and its doppelgänger moth are no more closely related than a human and an octopus. Their last common ancestor—a simple, wormlike marine creature—lived more than five hundred million years ago, before the split that led insects and birds to diverge. So why are they so alike? 

A Case Study in Convergent Evolution 

It’s a classic case of convergent evolution, says entomologist Akito Kawahara. Kawahara is Director of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History—the world’s largest collections-based research and education center for butterflies and moths. 

In convergent evolution, species independently evolve similar traits to suit the same ecological niche—in this case, drinking nectar while hovering. Other examples: Sharks’ and dolphins’ body shapes, primates’ and chameleons’ opposable thumbs, and the art of flying itself. It can happen within evolutionary classes, too. Swallows and swifts are both birds, of course—and both torpedo-shaped aerial insectivores with a striking resemblance to each other—but swifts are in fact more closely related to hummingbirds.
 

Some cases of avian-insect confusion are driven by mimicry: Where one species strategically resembles another, to deceive predators or prey. Cinereous Mourner chicks sport neon-orange plumage, for example, evoking the toxic larvae of flannel moths, and even bob like the larvae when threatened. Walnut hawkmoth larvae mimic songbirds’ alarm calls, a similar trick to scare attackers away. 

But in the case of moths and hummers, it’s simpler than that: “If you land on a plant, you're prone to predation,” says Kawahara. “If there's a spider or lizard on the flower, you'll get eaten. By hovering, you can avoid predation and move more quickly, systematically and efficiently, from flower to flower.” 

Hummingbird Moth vs Hummingbird: Which Is Bigger?  

When it comes to size, hummers and hummingbird moths face similar trade-offs: If they were much bigger, neither could beat their wings at such astounding speeds. Much smaller, and they wouldn’t have the muscle mass to do it. Still, there’s a viable range, and hummingbirds are generally bigger than the moths. The Ruby-throated Hummingbird’s wingspan is 3 to 4.3 inches, while the hummingbird clearwing’s is half that.

As pollinators, both help sustain healthy, biodiverse ecosystems across the United States. By reaching so deep into flowers, they can pollinate plants that might otherwise struggle to reproduce. An extreme case: Darwin’s hawkmoth has the world’s longest “tongue," its proboscis a staggering foot long, adapted to the star orchid—impressive, since this style of feeding is “like trying to hit the opening of a drink can with a two meters long straw in your mouth.” 

How to See and Help Hummingbird Moths 

As with hummingbirds, the moths are threatened by habitat loss and the overuse of pesticides. To support them, consider planting native nectar-bearing plants, especially sweet-smelling, colorful flowers like bee balm, verbena, salvia, honeysuckle, phlox, and butterfly bush. And think twice before raking up leaves—the larvae spin their cocoons in leaf litter in the colder months, especially beneath host plants like viburnum, cherry, and plum (leaf litter is good for birds, too). 

Look out for hummingbird moths on bright, sunny days. In the United States, midsummer is the best time to spot them. (Spring and summer are also when America's migrant hummingbirds are back and active, leading to the double takes.) These moths live throughout the United States, from Alaska to Florida, so keep an eye out no matter where you are. Hummingbird clearwings are most common in the eastern United States, though, snowberry clearwings are found across the country, and the Rocky Mountain clearwing, which also looks strikingly like a bumblebee, ranges throughout the intermountain west. 

We might find these moths amazing, but not every insects gets that privilege. And yet they're all critical to life on earth. “There's still tremendous negativity towards insects,” Kawahara says. But it doesn't have to be that way. To more deeply appreciate bugs, consider bugwatching. And if you're already a convert, introduce your friends to invertebrate life. In hummingbird moths, they might just find their spark insect—and worlds of wonder will follow in its wake.