Meet the Fierce Imperial Moth Caterpillar

The Imperial moth caterpillar is about 3-4 inches long, green or brown and spiky, lined with white spots with black rings around them, one per segment. The Imperial moth caterpillar's whitish hairs are sparsely distributed and may cause some skin rash.

How to Identify Imperial Moth (Eacles Imperialis)

Imperial moth
Imperial moth

The adult Imperial moth, scientific name Eacles imperialis (Drury) order Lepidoptera, family Saturniidae, and subfamily Ceratocampinae, has 3 inches to 7 inches (8 cm to 17.4 cm) wingspan.

The Imperial moth is highly variable in appearance, and females are larger than males. Males have hairy antennae and tend to be more heavily marked than females.

The Imperial moth is yellow with spots, lines, and splotches of purple or light to dark brown. The legs are usually covered in purple hairs.

These moths of North America emerge before sunrise and mate. The males are the first ones to emerge before the females. Females lay eggs at dusk, either singly or in groups. The oval-shaped flattish eggs are laid on both sides of the host plant leaf.

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The eggs hatch in 10 days to 2 weeks, the larvae being about 0.39 to 0.59 inches in size. Newly hatched larvae eat the eggshell after they emerge. Adult Imperial moths have reduced mouthparts; they don’t eat and are short-lived.

Imperial Moth Caterpillar: Description, Behavior, Instars

Imperial moth caterpillar
Imperial moth caterpillar

An Imperial moth caterpillar is a 4-inch long dark blackish-brown larva with fine whitish hair. Its body sides are lined with white barbs and black rings. The larva is harmless and does not sting or stab.

The larva undergoes five instars. At the end of each instar, a small amount of silk is spun around the major vein of a leaf, where the larva will clasp on with its prolegs. The caterpillar molts with each new stage.

First Instar

The first instar larvae are orange with black bands. The second and third thoracic segments have two long, black spikes with white tips. The eighth thoracic segment has a single large spike. Other thoracic segments have shorter spikes.

Second Instar

Larvae are much darker than the first instar, with shorter spikes. There are also some fine hairs on its body.

Third Instar

Spikes are much shorter, and the head is darker.

Fourth Instar

During this instar, the caterpillar has shorter spikes and longer hairs. Color variants are common in this instar.

Fifth Instar

Larvae are fully grown and are approximately 3 to 5.5 inches ( 7.5 cm to 10 cm ) long. The larvae have varying colors, from light to dark brown, green, or burgundy. At the end of this instar, the larvae don’t spin into cocoons; rather, they burrow into the soil and pupate.

Caterpillar Host Plants

The Imperial moth larvae feed on a variety of host plants. The most common and favorites include sycamore, oaks, eucalyptuses, and cedars. Other host plants are:

  • Maples (including boxelder)
  • Sweetgum (Liquidambar styraciflua)
  • Sassafras
  • Hickory
  • Basswood
  • Pines (Pinus)
  • Elm
  • Spruce

Where Are Imperial Moths Caterpillars Found?

Imperial moths prefer to live in woodlands, rocky mountains, and the Atlantic coast, anywhere where deciduous trees and shrubs are found.

Imperial moth subspecies are common from Canada to Argentina. In the US, they are found in Southern New England, the Florida Keys, and the southern Great Lakes region to central Texas, eastern Nebraska, and Maryland.

Is the Population in Decline?

The distribution of the Imperial moth widely extended up to the far north over its life history. Unfortunately, the moth has retreated from these areas beginning in the middle of the 20th century.

The disappearance of the Imperial moth in these areas has been attributed to the following:

  • Loss of its habitat to development
  • The widespread use of insecticides and pesticides
  • Increased usage of attractive artificial light sources
  • Introduction of parasitoids for control of the gypsy moth
  • Climate change

Most Common Predators

Predators of the Imperial moth caterpillar include birds, mammals, and insects.

Although the pupae may gain protection from birds by pupating in underground cells, they might become victims to mammals that dig in the soil.

The adult Imperial moth gains protection by camouflaging amidst dead yellow leaves on the forest ground.

Parasitoids include five species of tachinid flies and one species of ichneumonid wasp:

  • Fabricius
  • Aldrich
  • Williston
  • Van der Wulp
  • Sabrosky
  • Provancher

How to Care for Imperial Moth Caterpillars?

Here are some easy steps to rear the Imperial moth caterpillar to the moth stage:

  • Place the caterpillar and its host plant foliage, like pines, in a large container.
  • Provide fresh foliage daily.
  • Place 2 or 3 inches of loose, moist soil at the bottom of the container to help with pupation.
  • Ensure the container is large enough to accommodate the adult moth’s size when it emerges.

Can Imperial Moth Caterpillar Sting You?

Although the Imperial moth caterpillar might be huge and scary-looking, it is harmless, and its bristles and hairs don’t sting.

Its long hairs might cause some itchy rashes or allergic reactions in some people.

Still, don’t handle the caterpillar with bare hands. Use a pair of forceps or tweezers to avoid contact.

What to Do if This Caterpillar Stings?

If your skin happens to react to some subspecies of Imperial Moth caterpillar, there’s no specific remedy for the rash caused by this caterpillar.

For the most part, you can treat the rash like any other insect sting. This means washing affected areas with soap and water, applying a cold compress to ease pain, and taking an antihistamine if necessary. If the rash is severe, you should seek medical attention.

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