Despite appearance, nothing sinister about Hickory Horned Devil

Randy Drinkard Troup extension agent

August 30, 2013

Is Troup County being invaded by monsters from outer space? Aliens from the moon or Mars? Well, we are being invaded by a mysterious creature that does look a bit alien called the Hickory Horned Devil. These are scary caterpillars that are currently feeding on the foliage of various trees in the LaGrange vicinity and being spotted by local citizens who are calling the Extension office.

Description: Young Hickory Horned Devil caterpillars may be orange or brown with a greenish tint, but mature caterpillars are a striking green with black and white markings down the sides of their bodies. Both the young and older caterpillars possess pairs of large black-tipped red horns near the head and black spines down their backs.

Mature Hickory Horned Devil caterpillars are quite large and can grow up to 5.5 inches long. Overall the caterpillar resembles a ferocious dragon, but it is not dangerous or harmful. The spines are not poisonous and not very sharp.

The attractive adult moths are known as regal or royal walnut moths. They are heavy-bodied moths with rusty orange and yellow-striped bodies. Their forewings are grayish with rusty-orange veins and large yellow spots. Typically the wingspan measures between 3.75 to 6 inches across.

Damage: Both the caterpillar and the adult moth are completely harmless. The hickory horned devil is not considered to be a pest and does not require any control measures.

Habitat/Distribution: These caterpillars commonly feed on various species of hickory, as well as persimmon, sumac, sweetgum and walnut.

Life Cycle: This insect has a complete life cycle of egg, larval, pupal and adult stages. In late summer, mature caterpillars burrow into the ground where they pupate over the winter. The following summer newly emerged adult moths climb out of the ground and crawl up nearby vegetation to expand their wings.

Females emit pheromones to attract males, who may fly several miles in search of mates. Mated females lay eggs on host plants. Adult males and females do not have functioning mouthparts and do not feed. They die about a week after emergence. Typically there is one generation per year.

Control: The hickory horned devil has never been reported to be abundant enough to be considered a pest and appears to be less common than in years past. Because they are harmless to people, no pesticide recommendation seems to be appropriate.

Interesting Fact: This is the largest caterpillar found in North America but it does not turn into the largest moth.

Randy Drinkard is a technical writer for The UGA Center for Urban Agriculture and ANR Agent for Troup/Meriwether Cooperative Extension. The Troup County Extension office is located at 114 Church St. in LaGrange and may be reached at 706-883-1675, Monday through Friday, 8 a.m. to 5 p.m.