Achemon Sphinx Caterpillar

by Katie Bowell, Curator of Cultural Interpretation

Last week, a big, squishy caterpillar that looked a lot like this guy

Caterpillar!

was spotted crawling across the museum’s courtyard by some sharp-eyed visitors. A little research on Bug Guide and Butterflies and Moths of North America revealed that we’d had a visiting Achemon sphinx caterpillar (Eumorpha achemon), one of the hornworms.

Many gardeners will be familiar with one of the Achemon’s relatives, the Tomato hornworm (Manduca quinquemaculata).

Tomato Hornworm

In fact, when museum staff first looked at our then-mystery caterpillar, we thought we’d found a relative of the Tomato hornworm – they look so much alike. Well, they look alike with one exception: our caterpillar didn’t have a “horn” at the end of its abdomen. Well, it turns out that the Achemon caterpillars loses its terminal “horn” after its first molt (most caterpillars will molt, or shed their skin in order to grow, five times) and replaces it with a single eyespot marking. They’re still hornworms, just without the horn! And instead of eating tomatoes, Achemon feeds on Virginia creeper, grape and other related vines.

As you can see from the distribution map, the Achemon sphinx moth is found in pockets throughout the United States and Mexico.

Achemon sphinx distribution

Here in Colorado, the moth is found along the Front Range. In our colder climate, the moths produce one generation/year and you see full grown caterpillars in late August and early September. The caterpillar we saw looked pretty full grown to me, so I wouldn’t be surprised if it was looking for a suitable place to pupate under the soil (which is where hornworms go to change into moths). And once our caterpillar’s done pupating? We’ll have to keep our eyes out for one of these:

Achemon Sphinx Moth

Check out the proboscis (tongue) on these guys!

Achemon Sphinx Moth Feeding