A tomato hornworm turn into a large moth called the five-spotted hawkmoth. That fat green caterpillar on your tomato plant will burrow into the soil and change form. It comes back out as a fast-flying moth with gray-brown wings. You might mistake it for a hummingbird when you see it at your flowers.
When I first dug up a hornworm pupa, I had no idea what it was. I was turning my garden soil in late fall and found a dark brown case about 2 inches (5 centimeters) long. It had a curved piece sticking off one end like a tiny handle. I put it in a jar with some soil and kept it in my garage over winter. By early June a stunning moth pushed its way out, and I watched it pump fluid into its wings until they spread wide. That moment hooked me on insect life cycles.
The hornworm moth metamorphosis goes through four stages. Your caterpillar feeds on tomato leaves for about three to four weeks as it grows through five size stages. When it reaches full size, it drops off the plant. It digs 4-6 inches (10-15 centimeters) into your garden soil. Down there it sheds its skin and forms a hard pupa. That pupa has a curved case on the front that holds the moth's future proboscis.
The five-spotted hawkmoth that comes out looks nothing like the green caterpillar it used to be. You'll see gray-brown wings with wavy dark lines across them. Its thick body has five pairs of orange-yellow spots along each side. UC IPM data shows these moths can have wingspans up to 5 inches (12.7 centimeters). The full cycle from egg to adult moth takes about two months during warm summer weather.
You'll most likely spot these moths at dusk near your flower garden. They hover in front of blooms just like hummingbirds do while feeding. They uncoil a long proboscis to reach nectar deep inside tubular flowers. Your moonflowers, petunias, and jimsonweed attract them the most. This makes them important pollinators of night-blooming plants that you grow in your yard.
In warm areas, you may see two rounds of moths in one growing season. The first group flies by late May. Their offspring hit your garden as caterpillars in mid to late summer. In cooler areas, hornworms produce just one generation per year. Those pupae spend the whole winter underground waiting for warm soil to trigger their emergence in spring.
In my experience, knowing this life cycle helps you plan your garden defense better. Till your soil in late fall and early spring to expose pupae to cold weather and hungry birds. You won't stop every moth from showing up, but you can cut the numbers before the season starts. And when you spot one of these moths at your flowers, take a moment to appreciate your former garden pest in its final form.
Read the full article: Tomato Hornworm Guide for Gardeners
