A Field Guide to Identifying Yellow and Black Striped Caterpillars

Here are some tips and photos to help you identify the most common yellow and black striped caterpillars

Characteristics of Yellow and Black Striped Caterpillars

• Prominent alternating bands of yellow and black are the defining feature. The width and sharpness of the stripes aids identification
• Look for any additional colors like white blue orange, or red spots or tufts. Hairiness, spine density, head shape and size are also important clues.
• Note the host plants the caterpillars are feeding on. Many species have preferred plant families.
• Yellow and black signals warning coloration in some species, advertising their toxicity or unpleasant taste. Others mimic this pattern for protection.

12 Common Yellow and Black Caterpillars

1. Cinnabar Moth Caterpillar

• Found on ragwort leaves.
• Thick horizontal stripes of alternating yellow and black.
• Grows up to 2 inches long.
• Toxic; ingesting ragwort makes them distasteful to predators.

2. Yellowneck Caterpillar

• Feeds on cherry, elm, and basswood leaves.
• Has long black spikes radiating from yellow bands.
• Toxic quills can sting human skin.

3. Io Moth Caterpillar

• Eats leaves of cherry, willow, elm and other trees.
• Has spiky branched spines with black tipped yellow or white tufts.
• Grows over 2 inches long.

4. Saddleback Caterpillar

• Named for its brown “saddle” markings and green body.
• Has dangerous spines that inflict painful stings.
• Feeds on a variety of trees and shrubs.

5. Fall Webworm

• Weave messy webbed tents around branches as they eat leaves.
• Yellow or pale green with sparse fine hairs.
• Feed on over 600 types of trees.

6. Gray Dagger Moth

• Yellow with black dagger outlines pointing backwards.
• Long thin tufts of hair run lengthwise along body.
• Eats elm, birch, oak, maple and other trees.

7. Orangedog Caterpillar

• Yellow with broad black stripes bordered by fine white lines.
• Covered in bristly orange spikes.
• Feeds on citrus, jasmine and other plants.

8. Yellow Woollybear Caterpillar

• The larva of the Isabella Tiger Moth.
• Very fuzzy yellow and black bands of hair.
• Eats a wide variety of plants and trees.

9. Yellowstriped Armyworm

• Larva of the beet webworm moth.
• Yellow with black stripe down center dotted with orange.
• Major agricultural pest of many crops.

10. Sycamore Tussock Moth Caterpillar

-Yellow with black bands and four white hair tufts.

• Feeds on trees including sycamore, ash, oak and walnut.
• Hairs can irritate human skin.

11.Large Yellow Underwing Caterpillar

These plump, lemon-yellow caterpillars have a series of black dots running down their backs. They are the larvae of a moth called the large yellow underwing. As the name suggests, the moths have brightly colored hindwings.

12. Yellow-Tail Moth Caterpillar

The yellow-tail moth caterpillar (Euproctis similis) is mostly black but has yellow markings towards the rear end. It feeds on a variety of trees and shrubs.

With some basic detective work, you can easily identify whether yellow and black caterpillars are helpful pollinators or harmful invaders in your yard. Then make informed choices about managing their populations if needed. Appreciating their diversity transforms them from garden pests into fascinating miniature wildlife.

Life Cycles

The black and yellow caterpillars all transform into moths or butterflies to reproduce. Here is a brief overview of their life cycles:

• Cinnabar Moths – After mating, female cinnabar moths lay clusters of eggs on ragwort plants in the summer. The eggs hatch into caterpillars that feed on the ragwort for a few weeks. They then spin cocoons and overwinter as pupae, emerging as adult moths the next summer.
• Large Yellow Underwings – These moths lay their eggs on a variety of broadleaf trees and shrubs in July and August. The caterpillars feed until autumn then overwinter in the soil as pupae. The adult moths emerge in late spring.
• Yellow-Tail Moths – Females lay batches of eggs on trees, shrubs, and herbs in summer. The caterpillars feed for several weeks then spin cocoons to overwinter in. The adult moths emerge the following spring.

Frequently Asked Questions About Yellow and Black Striped Caterpillars

Are yellow and black caterpillars poisonous?

Some species like the cinnabar moth and yellowneck caterpillar have toxic quills or venom and can sting if handled roughly. Teach children not to touch fuzzy caterpillars. Others are harmless despite their warning colors.

What plants do these caterpillars eat?

They feed on a wide variety of trees and shrubs. Cherry, elm, oak, birch, basswood, willow, sycamore, citrus, ash, and walnut are some favorite host plants.

Why do some caterpillars change color as they grow?

Caterpillars can change shade and pattern rapidly through molting. Their early instars are often differently colored than mature larva. This helps camouflage them while small and vulnerable.

How do you tell a yellow and black caterpillar from a yellowjacket?

Wasps like yellowjackets have more narrow bodies with a distinct waistline, along with six legs and visible wings. Caterpillars have soft, plump bodies in distinct segments and many small prolegs.

What other insects mimic yellow and black caterpillars?

Some sawfly larvae and beetle grubs mimic caterpillar warning colors like yellow and black bands. Look for subtle differences like legs and proleg count to distinguish between insect groups.

Can you touch fuzzy yellow and black caterpillars safely?

It’s best not to touch any caterpillars, especially hairy ones. While many are harmless, some have irritating hairs and spines. Teach children to look but not touch these intriguing garden creatures.

In your backyard habitat, yellow and black caterpillars play an important role in the food web. Learning to identify them by species offers insights into the diversity of life in even a small green space. So appreciate the chance to witness these colorful creatures up close, but let them munch on in peace.