One day we saw what we thought was a very small hummingbird on our lantanas. We had no idea we were seeing, for our first time, a Hummingbird Moth. We moved from the Tyler area to central Texas where we had a large bed of four o’clocks. We had a half dozen little “bugs” flying erratically about each night around dusk. With a camera we got a close up and discovered our “baby hummingbird” had six legs. It was a moth! Just about that time we saw an article in Birds and Blooms about hummingbird moths
Hummingbird moths are the adult stage of the hornworm caterpillar. Many of these moths have a superficial resemblance to hummingbirds in flight while they similarly feed from deep-lobed flowers. They, unlike the hummingbird, are not flighty and will feed and fly right in front of their “observers.” They are usually most active during late afternoon and dusk. Most adult hornworms, that is the moth, fly after dusk and are rarely observed except occasionally at porch lights.
There are at least three dozen different varieties of hornworms but the most common are those that produce the sphinx moths. Of the sphinx varieties the most common is the whitelined sphinx. The whitelined sphinx caterpillars vary in color but most are predominately green. They will grow to lengths of three inches or more and characteristically sport a flexible spine (horn) on the hind end.
More people are familiar with the hornworms associated with tomatoes and other related plants. They are pests in vegetable gardens. They chew leaves and they can rapidly defoliate a plant. They are often seen on tomatoes, peppers, potatoes and other related plants. However, many other varieties of hornworms will cause no significant injury to plants.
The caterpillars (the larvae) burrow in the ground to pupate. Pupation occurs, over winter, a few inches below the soil surface in a small chamber of packed earth. They will pupae in the soil in the vicinity of the previously infested gardens. They typically emerge in late May and June. The pupae are typically brown, two inches or more in length and many have a pronounced “snout” off the head end. The pupa comes alive and begins to twist back and forth and a moth quickly emerges.
The female moths lay large pearl-colored eggs on the upper surfaces of the leaves. The young caterpillars hatch and feed on the plant for a month or more. They have tremendous appetites and consume large amounts of leaves as they grow older and larger. After feeding, they wander away from the plant and pupate in the soil. In warmer climates, often a second generation will come in August or late summer.
Some people who enjoy the hummingbird moth will collect the worms and raise them somewhere away from their gardens.
A.R. Wynn,former Smith County Master Gardener
Texas A&M AgriLife Extension Service