Tomato hornworms and hummingbird moth caterpillars are closely related but not the same species. The confusion is understandable: both are large green caterpillars with a distinctive horn on their rear end, and both belong to the sphinx moth family. But the tomato hornworm becomes a five-spotted hawk moth, while the caterpillar most people call a “hummingbird moth caterpillar” becomes a hummingbird clearwing moth. They look different as adults, feed on different plants, and play very different roles in your garden.
Why These Two Get Confused
Both species are sphinx moths, a family known for hovering flight that resembles a hummingbird. The five-spotted hawk moth (the adult form of the tomato hornworm) is a large, gray, night-flying moth with a wingspan of about four to five inches. The hummingbird clearwing moth is smaller, with a wingspan of 1½ to 2¼ inches, a furry greenish-yellow or tan body, and a wide reddish-brown band across its abdomen. Unlike most moths, hummingbird clearwings visit flowers during the day, hovering briefly at each bloom to sip nectar with a long, straw-like tongue before darting to the next one. That daytime hovering behavior is what earns them the “hummingbird moth” name.
People often see an adult hummingbird clearwing in their garden and then find a fat green hornworm on their tomato plant, assuming the two are connected. They’re not. The hummingbird clearwing caterpillar feeds on viburnum, honeysuckle, and related shrubs. It’s green with an anal horn, much like the tomato hornworm, but it won’t touch your tomatoes.
How to Identify a Tomato Hornworm
Tomato hornworms reach about four inches long at maturity. They’re bright green with eight white “V”-shaped markings along their back, pointing toward the head, and a black horn (or “tail spine”) at the rear end. They’re often confused with tobacco hornworms, which look similar but have seven diagonal white stripes with black margins and an orange-red horn instead of a black one. Both species feed on tomatoes, peppers, eggplant, and other plants in the nightshade family.
Despite their impressive camouflage, hornworms leave clues. Look for dark green droppings on leaves and the ground below, stripped stems, and large irregular holes chewed through leaves and fruit. If you spot the damage, the caterpillar is usually nearby on the same branch or one directly above.
Life Cycle of the Tomato Hornworm
Hornworms overwinter as pupae buried in the soil. Adults begin emerging around mid-May in most regions. The moths lay eggs on the undersides of leaves, and first-generation caterpillars appear by late May or early June. After feeding for about three weeks, the larvae burrow into the soil to pupate. First-generation adults emerge by mid-July, and a second generation of caterpillars is active from early August through early October. That second wave often catches gardeners off guard, doing heavy damage to late-season tomato plants.
The Hummingbird Clearwing Caterpillar
Hummingbird clearwing moths lay pale green eggs singly on the underside of leaves in early spring. The caterpillars that hatch are green with a well-developed horn on the rear, making them look like small hornworms to an untrained eye. The key difference is where you find them: these caterpillars feed on viburnum, hawthorn, snowberry, and similar shrubs, not vegetable crops. They’re generally not a garden pest, and the adult moths they become are considered beneficial pollinators.
Parasitic Wasps and White Cocoons
If you find a tomato hornworm covered in small white, rice-shaped cocoons, leave it alone. Those cocoons belong to a tiny parasitic wasp called Cotesia congregata. The female wasp lays around 65 eggs (sometimes over 100) directly into the caterpillar’s body. The wasp larvae develop inside the hornworm, eventually chewing their way out and spinning those white cocoons on the caterpillar’s skin. The hornworm stops feeding and dies shortly after.
Most gardeners adopt a live-and-let-live policy with parasitized hornworms. The wasps that emerge will go on to parasitize more hornworms, providing free, ongoing pest control. Killing a cocoon-covered caterpillar means destroying dozens of wasps that would have helped protect your garden.
Managing Hornworms in the Garden
Hand-picking is the most effective organic control for tomato hornworms once you know what to look for. Scout your plants once a day during peak season, checking the tops and undersides of leaves and along stems. Most gardeners simply squash collected hornworms or drown them in a bucket of water.
For younger caterpillars under two inches long, a Bacillus thuringiensis (BT) spray works well. This is a naturally occurring soil bacterium that kills caterpillars when they eat treated leaves. Larger hornworms often survive BT treatment, so timing matters. Since eggs hatch continuously through the season, a single application won’t solve the problem. Regular scouting is more reliable than spraying alone.
To reduce next year’s population, pull up spent tomato plants in fall and cultivate the soil. This exposes overwintering pupae to cold, predators, and drying. Done thoroughly, fall tilling can kill over 90% of the pupae in your soil, making the following season much more manageable.
Which One Is in Your Garden
If you found a large green caterpillar on your tomato, pepper, or eggplant, it’s almost certainly a tomato or tobacco hornworm, not a hummingbird moth caterpillar. Check the horn color: black means tomato hornworm, orange-red means tobacco hornworm. Both are garden pests that can strip a plant overnight.
If you found a green caterpillar with a horn on a viburnum, honeysuckle, or ornamental shrub, you’re likely looking at a hummingbird clearwing caterpillar. These rarely cause significant damage to their host plants and will eventually become the charming, pollinator moths that hover at your flower beds. There’s no reason to remove them.