How to Identify a Bedstraw Caterpillar Horn

By Frank Whittemore
caterpillar image by vladislav susoy from

The Bedstraw Hawk moth caterpillar is the larval form of the moth of the same name. Common in northern North America and Europe, the moth is a fast moving insect with swept-back wings that give it a streamlined appearance. The caterpillar can vary widely in color, however it can be identified by a single red horn on its tail. The horn, when added to other characteristics, can help differentiate the Bedstraw Hawk moth caterpillar from other moth larvae, such as the Hydrangea Sphinx moth, which also has a red tail horn but different body color.

Look for a small, bright red horn that projects from the tail end of the caterpillar. The horn of the Bedstraw Hawk moth caterpillar is relatively short, pointing outward from just before the rump with a slightly down-turned end.

Examine the body coloration of the caterpillar, which can range from green, to brown, to nearly all black. Some variations display distinct black bands across the body at regular spacing along a green background. Others present two black stripes with yellow spots that run the length of the the top of the caterpillar. Still, others are almost completely brown or black with yellow spots that run along the sides of the body. The head is typically colored the same as the body.

Assess the body of the caterpillar. Bedstraw Hawk moth larvae are elongated and worm-like. The skin is smooth and shiny with slight wrinkles on each segment. There are no hairs, silks or spines on this caterpillar. The caterpillar can reach a mature length of three inches before it begins to pupate.

Determine the feeding habits of the caterpillar. Bedstraw Hawk moth caterpillars can be found primarily on the plants of which they feed. These plants include woodruff, godetia, willow weed and gallium, also known as bedstraw, from which the insect's name is derived.