White-Lined Sphinx Moths

Q: What are those huge moths siphoning nectar from the evening primroses, fluttering around the catmint, hovering in front of the Red Feathers (below), and flocking (what do you call groups of moths, anyway?) around the lilac blooms?

A: They remind one of hummingbirds as they sip nectar through their long proboscises, so it’s easy to see howthey got one common name—Hummingbird Moth. However, these aren’t birds, but insects—sphinx moths in the family Sphingidae.

There are a lot of different kinds of sphinx moths (aka hawk moths)—around 1,450 species! One sphinx moth spends its childhood as the aggravating Tomato Hornworm, but the ones currently experiencing a population explosion here in Colorado are a different species—the White-Lined Sphinx Moth. These eat a variety of plants. A single caterpillar can quickly defoliate an evening primrose (one of their favorite snacks), and the female moth can lay up to 500 eggs at a time. Problems occur when large numbers of caterpillars hatch at once, as Eric Eaton describes on his blog “Bug Eric”:

…food plants can quickly become scarce as they are consumed, and the caterpillars are forced to “march” in search of literally greener pastures. These large scale “migrations” may cross rural roads creating a slick hazard as they are crushed under tires.

Ewwww!

Given the number of moths seen lately, you may have previously noticed the caterpillars with their bright colors, large size, and distinctive shape. (Image left: Whitney Cranshaw) Once fully grown, a caterpillar digs into the soil and creates a small space for itself. There it undergoes metamorphosis as a shiny, dark brown pupa. A few weeks later, the adult moth emerges to begin the cycle all over again. Because they live on nectar, adult moths don’t damage plants at all, and in fact may act as pollinators.

More than one generation per summer is possible, but if it’s late in the season the insect will overwinter as a cocoon, safe underground awaiting spring’s flowers.

Colorado’s Front Range is also currently being inundated by migrating miller moths, so it’s a pleasant change to find a moth that is so interesting.
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Article and (most) photos by Leslie Holzmann, Certified Colorado Gardener.