Tuesday, November 20, 2018
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The Heroic Cinnabar Moth

Cinnabar Moth. Click to view larger image.

He may look like a pretty butterfly, but this winged creature is actually a day-flying, evil-eradicating, heroic moth.

The Cinnabar Moth (Tyria jacobaeae) is a member of the Arctiidae (Tiger Moth) family — originally found only in Europe and western and central Asia — and is a relatively new resident to our area.

Initially introduced to Washington state in 1960, the Cinnabar Moth is part of a concerted effort to control the invasive poisonous plant — tansy ragwort — and all without the use of herbicides.

This is the time of year when you may see a Cinnabar Moth flitting through the wild grasses and plants in your neighborhood.

The Evils of Tansy Ragwort

Tansy ragwort (Senecio jacobaea) is a wild growing weed with a pretty yellow flower that can used as a source of yellow dye. But whatever mildly beneficial qualities the ragwort possesses, the good qualities are far outweighed by its poisonous nature:

“All plant parts are toxic, with the highest amount of alkaloids in flowers then leaves, roots and stems. Toxic properties are a possible threat to humans through food chain contaminants.” Source: Washington State Noxious Week Control Board

“Tansy ragwort is toxic, and can be lethal to cattle and horses … These toxic properties remain in cut plants found in hay. … Chronic, cumulative poisoning, and irreversible liver damage, including cirrhosis of the liver are the results of ragwort poisoning.” Source: Washington Department of Fish and Wildlife. 2006. South Puget Sound Wildlife Area Management Plan. Wildlife Management Program, Washington Department of Fish and Wildlife, Olympia. 67 pp.

Tansy ragwort flowers throughout the summer and grows on roadsides, in pastures, fields and cleared forested areas, at low and mid elevations. Ragwort contains many different alkaloids, making it poisonous to most creatures — but the Cinnabar Moth thrives on the invasive weed.

Both larvae and mature moths feed on tansy plants. The adult moths consume the nectar of the flowers, the larvae feast on the foliage and stems.

Meet the Hero

Cinnabar Moth (Tyria jacobaeae) larva feeding on tansy ragwort. Click to view larger image.

The larvae of the Cinnabar Moth can consume large amounts of the tansy ragwort alkaloids without a problem. In fact, the alkaloids are actually beneficial to the Cinnabar Moths, because as they absorb alkaloids, they also become a bitter bite in potential predators’ mouths.

The bright colors of both the larvae (yellow and black) and the moths (red and black) serve as universally readable warning signs of their foul taste.

Cinnabar Moth larvae also eat other plants in the Senencio plant family, including groundsels, dusty miller, and butterweeds, but the tansy ragwort is its favorite food.

Life Cycle of the Cinnabar Moth

Cinnabar Moth pupa. Click on image for larger view.

Adults moths emerge in late spring from overwintering pupae.

The Cinnabar Moth is brightly colored, day-flying moth. Their crimson hindwings are bordered with dusky black and their dark grey forewings have a red streak towards the front margin and two red spots on the outer edges

The female moth lays her eggs under the leaves at the base of the ragwort plant. Larvae hatch in about two weeks.

Their development takes about one month, after this, they pupate on the ground and remain in diapause (physicologically enforced dormancy) until the following spring.

View a Cinnabar Moth Video

Click image for larger view.

Tansy Biological Control – Cinnabar Caterpillar

Read More Online

ARKive – Cinnabar Moth
Land Care Research – Cinnabar Moth

Washington State Noxious Weed Control Board
Pacific Northwest Weed Control Handbook
Gardening in Western Washington

Buy a Great Resource Book at Amazon.com

Kimberly Mason is a freelance writer and photojournalist. She is the founder of The (Almost) Daily News website, enjoys using her Nikon to take pot shots at all things with wings and strives to learn something new every day. You can find her on Facebook, call her with questions or outdoors news tips at 360-269-5017, or email her at kim@almostdailynews.com.


  1. This is great news! We are always on the look out for tansy in the horse pastures. Hand digging and pulling, then bagging and putting in the garbage. It’s nice to know there is something out there that will eat it! Great pictures and article, again!

    • As I was writing this article it occurred to me that I must be seeing the Cinnabar Moth in my own back yard because there is a FOOD source here. Yikes! Then I thought, “I don’t have livestock, no worries.” But wait, I do! I have deer and elk to worry about.

      And you left a great reminder in your comment, Denise, we can’t just throw this weed into our compost pile. We have to bag it and put it in the garbage. Thank you for the reminder!

  2. I saw one in Kirkland, WA. I posted it to my fb page and a friend posted your link. I’m native to the Seattle area and have never seen one. So amazing. I thought the moth was a leaf floating in the wind at first. Was taken aback when I realized that it was a butterfly or moth. Just so gorgeous. Took photos.

  3. There no longer seems to be a priority on controlling Tansy in the PNW. Oregon State University used to distribute Cinnabar Moths, but is. I longer doing so.

  4. From England.
    The female arrived by herself about 6 weeks ago, in early June – she laid her eggs, and promptly died.
    Just a fortnight later, the eggs hatched, and the caterpillars were rapidly devouring one Ragwort plant, almost 4 foot tall. They finished this off in about 5 days. I thought, will I now have to move them to the next weed? Not on your life! These little fellows were off aggressively prospecting for more plants, many metres away from the first Ragwort, and were actively colonising and eradicating still more of the weeds, before they had a chance to go to seed. All the Ragwort has now been utterly destroyed, in my back at least.
    These creatures are a Godsend – I almost felt sorry for the Ragwort – but then…

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