A Summer Mystery: The Hummingbird Clearwing Moth in Wisconsin
The Great Outdoors | July 9, 2024
By Jackie Scharfenberg, Retired DNR Naturalist, Photo by: Judy Gallagher
On a summer afternoon as I sat on my front porch chilling, I saw something peculiar hovering around my flowers. First, I thought it was a ruby-throated hummingbird, but it was about half the size of a three-inch hummingbird. It was too big for a bumblebee and it did not look like a butterfly. With my handy binoculars, I focused on the tiny creature and noticed it had clear wings with dark veins and borders. The front wings looked longer than the back two wings. The plumb “furry” thorax appeared olive greenish with dark reddish-brown bands across the abdomen. When it flew by, I caught a glimpse of the white/light yellow underside. On its head grew two antennae with thicker bases and curved ends and attached to the thorax were six pale yellow plain legs. It reminded me of a sphinx moth, but they usually fly at night. Since I love nature mysteries, I kept watching the little flier.
It quickly dashed from one flower to another sticking its long proboscis into each bloom. When it stopped feeding, the proboscis coiled up like a party noisemaker. It fed on all kinds of flowers including petunias, verbena, butterfly weed, purple coneflowers, and bee balm preferring the pink and purple ones. I noticed it flapped its wings so fast that it made a soft buzzing sound.
Mysterious Creature
Armed with this information, I started searching my bug guide to figure out the identity of this odd insect. My search led me to hummingbird clearwing moth (Hemaris thysbe), a member of the sphinx moth family. I read that these moths are most active during the hottest part of the day until sunset – unusual behavior for a moth.
Their Young
Hummingbird clearwings are found throughout North America, but are most common in the eastern United States preferring a wide variety of open habitats from meadows to forest edges and suburban gardens. In the North they have one brood a year while in the South, they may have two broods.
After mating, females lay their pale green eggs individually on the underside of leaves favoring viburnum bushes but, will lay eggs on various other shrub leaves, as well. After a week, the caterpillars hatch. The young larvae feed on the underside of the leaves. When they get older, they forage at night on all parts of the leaves retreating to lower stems during the day. While researching I learned the caterpillars glow brightly under UV light, so I am going to get a blacklight and head out after dark to search for them.
The caterpillars come in two colors – green or brown. A pair of white stripes runs along the caterpillar’s back ending at its bluish horn while red spiracles (breathing holes) bordered in white line its sides. At four weeks old, the caterpillars spin dark brown, thin-walled cocoons under the leaf litter where they will overwinter. In late spring/early summer, they emerge as adult moths.
That proved a fun mystery to solve. Now, I will keep a closer watch for hummingbird clearwing moths hovering around my flowers and their caterpillars feeding on bush leaves.
