Gardeners often encounter large, green caterpillars known as hornworms, which can devastate plants. Many are also fascinated by small, hummingbird-like insects that hover among flowers, commonly called hummingbird moths. A frequent question arises: do these garden pests transform into the graceful, nectar-feeding moths? Exploring their distinct life cycles and characteristics reveals their true relationship.
The Hornworm’s Metamorphosis
Common garden hornworms are the larval stage of specific moth species, primarily the Tobacco Hornworm (Manduca sexta) and the Tomato Hornworm (Manduca quinquemaculata). These caterpillars are recognized by their large, green bodies, often reaching 3 to 4 inches in length, and a distinctive pointed “horn” on their posterior end. They are significant pests, mainly feeding on nightshade plants like tomatoes, tobacco, peppers, and eggplants.
Hornworms undergo complete metamorphosis: egg, larva, pupa, and adult. After feeding, mature larvae burrow into the soil to pupate. The pupa is a reddish-brown, hard-shelled casing where transformation occurs.
Adult moths emerge from these pupae. The Tobacco Hornworm develops into the Carolina Sphinx Moth, while the Tomato Hornworm becomes the Five-spotted Hawkmoth. Both are sphinx moths, characterized by heavy bodies and strong flight. These nocturnal adults feed on nectar, often seen hovering at flowers around dusk.
The True Hummingbird Moth
Insects commonly called “hummingbird moths” are typically Hemaris species, such as the Snowberry Clearwing (Hemaris diffinis) and the Hummingbird Clearwing (Hemaris thysbe). They are named for their resemblance to hummingbirds, displaying a similar hovering flight and soft humming sound while feeding. Unlike most moths, Hemaris species are active during the day, visiting various flowers.
These moths have stout, fuzzy bodies that can be greenish-yellow or olive and burgundy. Their wings are largely transparent with reddish-brown borders, earning them the name “clearwing moths.” This transparency results from scales falling off after their first flights. They use a long proboscis to sip nectar from deep flowers while hovering. Their larvae feed on plants like honeysuckle, snowberry, hawthorns, and cherries.
Are They One and the Same?
Despite their common names and some shared behaviors, garden hornworms and the moths typically known as “hummingbird moths” are not the same species. Hornworms are the larvae of Manduca species (Carolina Sphinx Moth and Five-spotted Hawkmoth), while “hummingbird moths” are Hemaris species (like the Snowberry Clearwing and Hummingbird Clearwing). Both groups belong to the Sphingidae family, also known as sphinx moths or hawkmoths.
The confusion largely stems from this shared family classification and the hovering flight style exhibited by both adult Manduca and Hemaris moths while nectaring. While Manduca moths are strong fliers and can resemble hummingbirds, Hemaris moths are specifically known for this mimicry, often mistaken for hummingbirds or bumblebees. They represent distinct branches within the sphinx moth family, each with unique life cycles, appearances, and host plant preferences.
Spotting the Difference
Distinguishing between the adult forms of these moths involves observing several visual cues. Adult Manduca moths (Carolina Sphinx Moth and Five-spotted Hawkmoth) are generally larger, with wingspans ranging from 3 to over 5 inches. Their wings are typically mottled gray and brown, often resembling tree bark, and they possess distinctive yellow or orange spots along their abdomen.
In contrast, Hemaris “hummingbird moths” are smaller, usually with wingspans between 1.25 and 2.25 inches. Their most notable feature is their transparent wings, bordered by darker scales, and their bodies often display more vibrant colors like olive-green, yellow, and burgundy, resembling bees or hummingbirds. Additionally, the caterpillars of Manduca species feed on solanaceous plants, while Hemaris larvae are found on different host plants such as honeysuckle or snowberry.