In the Garden:
Southwestern Deserts
February, 2011
Regional Report

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Sphinx moth pupal case.

Sphinx Moth

When I first moved to the Southwest and spied an adult sphinx moth plundering nectar from lantana blossoms at dusk, I thought it was a tiny, rather drab, hummingbird. In the low light, I couldn't get a good look at it, although its rapid darting from flower to flower and ability to hover in mid-air seemed impressively hummer-like to me.

Later, I learned that there are dozens of species of this moth known by various common names, such as hummingbird moth and hawk moth. White-lined sphinx moth (Hyles lineata) is a frequent visitor to low desert flower gardens and is likely the busy flier I first saw. It is quite pretty, with dramatic white and pink markings, although it seldom slows down enough to us to admire the detail.

If you are a vegetable gardener, you may be more familiar with, and perhaps frustrated by, the larval stage of other common sphinx moths, such as Manduca sexta or M. quinquemaculata, commonly called tobacco hornworm or tomato hornworm, respectively. You can easily recognize these chubby green caterpillars by white diagonal stripes and an obvious pointy "horn" arising from the back end. Their bright green color provides effective camouflage, and they are often difficult to spot on the undersides of leaves or along stems.

Hornworms chomp their way through tomato and pepper plants with considerable speed and gusto. I've found the best way to seek them is to look for their black, pellet-like droppings (frass), which show up more vividly against the green foliage and carefully look up and out from there. Handpicking is easy and you can set them in an obvious place for bird treats.

After fattening on your tomato plants, the larvae burrow into the soil to pupate. They overwinter in the soil, with the adult moth emerging when temperatures warm in spring or early summer. The hard pupal case is chocolate brown, about 1.5 to 2 inches in length. Today, I found one while tidying mulch around my aloe plants. I like the free mulch from a nearby tree, but it tends to drop and accumulate in piles. As I was spreading it around more evenly by hand, I undercovered the pupal case. When I picked it up, it wiggled its back end slightly. Upon careful scrutiny, I could make out the shape of its wings. Such unexpected discoveries in the midst of routine tasks are one of the delights of gardening!

Check out this website which contains photos of adult, larval, and pupal stages of a white-lined sphinx moth: http://www.birds-n-garden.com/white-lined_sphinx_hummingbird_moths.html.


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