Meet the sphinx moth: Nature’s daytime moths mimic hummingbirds and bees

Bee to the blossom, moth to the flame; Each to his passion; what's in a name?

— Helen Hunt Jackson, 19th century American writer, poet, and activist

When it comes to moth names, have I got some species for you. Let’s start with some moth and butterfly basics. While butterflies are out during the day, most moths are nocturnal. Butterflies rest with their wings held together above the body and have clubbed antennae. Moths rest with their wings spread and usually have feathery antenna.

How sphinx moths differ

Why am I talking about butterflies? Because sphinx moths are usually out during the day and could be confused with closely-related butterflies. But first, how did this insect earn the sphinx moniker? When resting, the old explanation went, their caterpillars would raise the front part of their bodies off a leaf or twig. This pose was thought to resemble the Great Sphinx of Egypt.

Recent research done with tobacco hornworms (aka the Carolina sphinx moth) at Tufts University offers a new and intriguing reason for the pose. The caterpillar is actually processing discomfort or pain in this state. The researchers note “ … this is a reversible, quiescent state that caterpillars assume when they experience mechanical disturbance in their surroundings.”

Hornworms, you ask? Take a look at the rear end. Some sphinx larvae have a smooth button rather than a horn.

Adult sphinx moths

Sphinx moths include some of the largest moths in the world. You can find approximately 1,450 species around the globe, 130 on our continent north of Mexico, and around 50 species in the Land of Lincoln.

They have a chunky body with a pointed abdomen that looks like a tiny football — a football powered by strong narrow wings. Their top speed is 30 mph, and males have been known to fly two miles in search for a mate. They also have very long tongues. Since they are nectar feeders, this long tongue is quite useful in siphoning their food from flowers.

Speaking of nectar feeders, this brings us to how it earned the hawk moth name. Some hawk moths can hover in the air, rapidly changing directions. They can even fly in reverse. In an example of convergent evolution, other nectar feeders have similar flight capabilities, including certain bats, hoverflies, and hummingbirds.

Makings things clear

This brings us to the first of two moths that inspired this article and have been spotted at Stillman Nature Center, the hummingbird moth (Hemaris thysbe). Not surprisingly, this moth is also called the hummingbird clearwing. As you might expect, this is not the only sphinx moth species with this common name.

In any event, the larvae will eat honeysuckles, hawthorns, cherries and plums. Adult moths gather nectar from a variety of flowers, including bee balm, clover, thistle, milkweed, vetch, and honeysuckle. Since these plants are widespread across Illinois, the hummingbird moth is also common in our suburban gardens and neighborhoods.

They have two generations a year, so adult hummingbird moths can be spotted from April through September. The caterpillars pupate in a silk cocoon spun on the ground among leaf litter.

The combination of extensive transparent areas on the wings and the feathery looking tail is supposed to fool a hungry bird into thinking that this large, well-armed bee should just be left alone. Biologists would call this an example of Batesian mimicry, where one harmless species mimics a harmful one.

The bumblebee moth (Hemaris diffinis), as the name suggests, is also an example of Batesian mimicry. Its larvae dine on honeysuckles, dogbane and snowberry. It is also known as the snowberry clearwing. Adult bumblebee moths gather nectar from thistles, red clover, cardinal flower, hawkweed, milkweed, dogbane, mock orange and phlox, just to name a few.

Although the black and yellow markings on this sphinx moth’s body enhance its bumblebee appearance, there is a difference in behavior. Actual bees land and crawl into a flower in order to abscond with pollen. They don’t hover and reach out with a long tongue like the sphinx moths do.

Also, like its larger cousin, the bumblebee moth has two generations a year. Adults can be seen from early spring into autumn.

Given this species’ eclectic tastes, it is a relatively abundant species, or should I say, it was relatively abundant.

Moth numbers declining

I know you’ve heard this before. Lack of habitat, climate change, and pesticide use are negatively affecting the numbers of moths and butterflies. I’d like to drill in on pesticide use. In 1980, I worked at a nature center in suburban New York City during a major spongy moth (formerly known as gypsy moth) outbreak. Most of the deciduous trees had been stripped of their leaves. Chemical insecticides were being sprayed that killed a variety of caterpillars as well as honey bees.

So, people looked to more natural solutions such as bacteria, parasitic wasps, and insectivorous birds. In this vein comes the parasitic tachinid fly (Compsilura concinnata). It was brought over from Europe in 1906 to help control spongy moths.

As is often the case, time was not taken to test and research this fly’s habits before it was released. It turns out that the tachinid fly is a generalist and not too picky about species of caterpillars it lays its eggs on. According to David L. Wagner at the University of Connecticut, this fly will lay eggs on over 200 species of North American caterpillars.

Well-meaning managers and biologists have released tachinid flies everywhere from New England to Minnesota and California. One can’t help but wonder if this cure is worse than the disease.

Centuries ago, British poet and visionary William Blake put it succinctly, “Kill not the moth nor butterfly, for the last judgment draweth nigh.”

Mark Spreyer is the director of the Stillman Nature Center in Barrington. Email him at stillmangho@gmail.com.