During a walk in my local wildlife garden we noticed the first Cinnabar Moth (
Tyria jacobaeae) caterpillars of the year, and an adult also flew by. The caterpillars clustered at the flower heads of Ragwort (
Senecio jacobaea), which they prefer as food, and had defoliated the plants quite a bit. Many had already left in search for greener pastures and were around the ground or wandering over other plants. Cinnabar Moth caterpillars have a strong tendency to cluster together, an antipredator behaviour.
This behaviour , however, gradually dissapears as the larvae grow so that fully grown fifth instar larvae are actually agressive to each other and tend to be found spaced out in the plants.
Adults emerge in late spring from overwintering pupae and after mating, female lay eggs in the basal leaves of ragworts. Larvae hatch in about two weeks and their development takes about one month, after this, they pupate on the ground and remain in diapause until the following spring.
This moth is often active by day and therefore easy to spot due to its contrasting coloration, but they are most active at dawn and dusk. When they fly, their pink hindwings are quite apparent and they can be taken for some exotic bright pink butterfly. The bright colours of the moth and particularly, the striking yellow and black stripy pattern of the larvae are a warning sign of their distastefulness to vertebrate predators, a phenomenon called aposematism. The larvae ingests and stores in its tissues toxic alkaloids from the foodplant and the adult also synthesizes additional toxins itself. Surprisingly, many invertebrate predators feed on eggs and caterpillars of this moth.
Given that Ragwort is a toxic plant for horses and has been introduced in several countries where it has become an invasive weed, a lot of effort has been directed to study the ecology of the Cinnabar Moth as a way of controlling Ragwort.
More information
J.P. Dempster (1982). The Ecology of the Cinnabar Moth, Tyria jacobaeae L. (Lepidoptera: Arctiidae) Advances in Ecological Research, 12, 1-36 DOI: 10.1016/S0065-2504(08)60076-8
This is a great blog entry! I think cinnabar caterpillars and moths are such interesting little creatures. I found your blog on Google when searching for information about cinnabar caterpillars for my blog entry about them. I added a link to your blog at the end of it. (Here it is in case you want to take a peek: http://pnwnature.blogspot.com/2010/08/good-bye-to-dear-cinnamon-our-cinnabar.html )
ReplyDeleteThank you Jay! I am glad it was informative. I have never tried to keep them, but I think after reading your post you guys probably got a large caterpillar ready to pupate. I would try and find small ones next year to show the kids how much they eat and how fast they grow.
ReplyDeleteI've found some caterpillars from ragwort that has been pulled and is ready for burning. Now how do I help them survive so they can eat more ragwort - a breeeding program would be good.
ReplyDeleteWe're overrun with ragwort now, and there are very few caterpillars. I remember there being loads of caterpillars and them stripping whole plants of ragwort.
i found some of these caterpillars on some ragwort by the beach, i took them home and i am now waiting for them to pupae. they also eat common groundsel but they prefer ragwort. its a shame they take a year to evolve but its worth it when youve got a ragwort infestation!
ReplyDeleteWe have found some of these caterpillars and I'm wanting to keep them to show my children see how they change. We found 3, and I would like to know some more info on how I can help them grow n keep them. Please can you help as it would be lovely for the kids see them grow n change
ReplyDeleteCheers, steph
I'm infested all year every year in my garden. Anybody who wants them come take them gladly :P x
ReplyDeleteThis creature is destroying my Sandal wood tree leaves. What should i do? Is it dangerous to tree growth ?
ReplyDeleteHi. We keep finding the same looking catepilcater in our home. Any ideas why they going in? We have no idea where they coming from as we don't have big garden or loads of plants arroun. I never seen them in the garden before. Any ideas whtthats happening and how to stop them from going in?
ReplyDeleteHi, we have loads of these beauties in our garden. My son has started collecting them in jam jars, some of which have turned into chrysalises. Will the hatch this year or are they now waiting for the next spring?
ReplyDeleteThey will emerge in spring... Leave them outdoors, they need to feel the winter..
ReplyDeleteGreat, thanks.
DeleteWhy does the cinnabar catipillar only eat ragwort? Will, age 5.
ReplyDeleteHi Will, That is a really good question! The cinnabar has adapted to make the best of this food plant, and it benefits also from using the plant's toxic chemicals to defend themselves from predation from birds. Their yellow and black patterns advertise their toxicity to the birds. Young birds might attack the caterpillar only out find out that they don't taste very nice. That particular caterpillar may die from the attack, but its brothers and sisters will survive, as birds are unlikely to forget the caterpillar colour pattern. Many toxic insects have a black and yellow or black and red pattern, which has evolved for the same reason.
ReplyDeleteHi. I am from Pretoria in South Africa. These worms have infected my prickly pear trees. After a while the tree collapses and die. For me it is a pest and I tree ti get rid of them. Regards. Jannie le Roux. Tel +27833266283
ReplyDelete"Unknown said...
ReplyDeleteHi. I am from Pretoria in South Africa. These worms have infected my prickly pear trees. After a while the tree collapses and die. For me it is a pest and I tree ti get rid of them. Regards. Jannie le Roux. Tel +27833266283
15 April 2020 at 09:44"
You're confusing the Cinnabar moth caterpillar (Tyria jacobaeae) with the Cactus moth caterpillar (Cactoblastis cactorum). The Cinnabar moth is not found in South Africa.
It’s crazy how long they take to hatch from their pupae! We are waiting for two cinnabar moth pupae to hatch at our house! We have named them Speedy and Titch because one of them is small and the other is fast! ;-)
ReplyDeleteI used to cut Ragwort down in my garden until I saw those lovely caterpillars and read up on them … now I just let nature do it’s thing
ReplyDelete