Regal moths, which grow from hickory horned devil caterpillars, are hard to miss when you find them in your yard. Their thick bodies sport wings often striped with yellow and orange, many showing yellow spots. Their most amazing characteristic is their size -- males can top out at about 6 inches across. Even though they're big, there's no need to worry they're going to kill your plants by eating them.
When They Eat
Regal moths start out their lives as eggs that hatch into larvae, known as caterpillars. Instead of showing their spiky heads in the spring like many caterpillars do, the hickory horned devil caterpillars usually appear in early to mid-summer. They live for about 35 days as a caterpillar, spending most of their time eating leaves to help them grow to their full size of 4 1/2 to 6 inches long. Most are ready to pupate, or cocoon themselves to change into moths, by late summer to early fall. Their main fare thrives in the heat of summer.
They aren't called hickory horned devils for nothing -- these caterpillars commonly frequent hickory trees, munching on the leaves. They also enjoy leaves from trees, such as butternut, walnut, persimmon, cherry and ash. Adult moths don't live very long, so the females don't travel far from the trees they grew up in as caterpillars. They lay eggs on or close to preferred food sources, so the caterpillars have leaves to eat immediately upon hatching without having to crawl around and search for food.
What Moths Eat
After eating voraciously for their last few days, caterpillars burrow into the soil to pupate. They typically stay there for 11 months, but some take 23 months to complete their metamorphosis. When they emerge in the summer as moths, they don't have working mouth parts, which means they can't eat so your plants are safe from these moths. By the end of their second day as moths, they mate, and the females lay eggs by the end of their third day. Because they haven't eaten in months and still can't eat, they typically live a week or less as adult moths.
Dangers to Your Yard
Although the big caterpillars can put away a large amount of leaves in their average 35 days of life, they don't pose a threat to your trees. These moths aren't prolific, so the small numbers of caterpillars can't decimate your yard. They're relatively selective about their diets, so it's unlikely they would move from their host tree to a nearby tree of an unsuitable species. Because they don't pose a danger to your trees, you usually won't need pesticides or other forms of control.
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