I hadn’t actually seen one of these until only a couple of months ago. Not their adult, flying form anyway. But when you see this beautiful vamp spread its wings it truly is something to behold. Seeing it Unfold its seemingly blood-stained black cape to reveal a bold red lining beneath. This moth is fashion goals!
And they’re no slouch in the form I know them best as, their caterpillars, either. The caterpillar of the cinnabar moth is a relatively large and wonderfully tiger-striped orange-and-black tubes that feed exclusively off of ragwort.
This, incidentally, is one of the reasons for their colour. I’m sure you’re aware that often brightly coloured creatures – the black-and-yellow of wasps, the various shades of reds, blues and yellows of poison dart frogs, those octopuses with iridescent blue rings – are ‘warning signs’. It’s something we’re often taught very young. The technical term for this is aposematism, the use of bold colours or striking patterns to act as a warning sign to potential predators that you’re not worth the risk. Effectively the naturally evolved form of the expression “come and ‘ave a go if you think you’re ‘ard enough!”
In the case of the cinnabar moth they get their noxiousness from the ragwort they eat. Ragwort (also known quite humorously as ‘stinking willie’) is a common plant native to the UK. If you’ve ever seen tall bushes of yellow-orange flowers on a medium-to-tall thin stem, likely that’s ragwort. These plants contain a cocktail of chemicals called ‘alkaloids’ that can have some nasty effects if ingested by the wrong creatures – sometimes including people. For the caterpillars of cinnabar moths, however, they gift them the protection of toxicity to many predators. Even where they are not actually harmful they can have a bitter taste or basically be unpalatable to predators, discouraging predation.
The adult form retains this unpalatable trait, so the moths are also undesirable to predators! It’s very clever.
Now I wouldn’t be doing my job as a wasp advocate if I didn’t mention something here. You see cinnabar moths lay loads of bloody eggs – batches of around 40-50 are not uncommon, they may lay a few batches – You’re looking 300 eggs. That’s a lot of potential caterpillars.
And there is basically not a single insect that doesn’t have a wasp that hunts or parasitises it! This is especially true of lepidopterans – moths and butterflies. So if you ever happen upon a clutch of caterpillars I do strongly urge you to watch them for a while and keep an eye out for wasps nearby. I saw it recently with a nest of small tortoiseshell caterpillars. But the most amazing spot was in some ragwort in an alley behind a housing estate.
There I saw a whole bunch of cinnabar moth caterpillars and thought “Hmm, I’ll watch these!” and got to see this!
A parasitoid wasp sticking an egg into its caterpillar host! Amazing! As someone hugely into predator-prey interactions and wasps this was a blessing to see.
You may think it cruel. You may in your existing prejudice of wasps think this is mean, that it is horrible that this wasp is doing such a thing to this beautiful caterpillar that turns into a beautiful moth but – as mentioned – they lay hundreds of eggs! They can’t all live and if they do they have been known, when low on food, to cannibalise!
Predators help regulate prey numbers. Wasps aren’t just doing this for cinnabar moths, they’re doing it to the white butterflies that eat your cabbages, the flies that give you E. coli and the aphids making your flowers less vibrant. Wasps are our friends when it comes to maintaining healthy ecosystems, Let them do their thing without prejudice and they are of huge benefit to us and the wider natural world. They are ensuring that there’s some ragwort left for the next generation of cinnabar moths!
There, I got back on subject! I do love wasps, though.
These moths are quite large and conspicuous, are well distributed across the UK and are known to fly during the day – So they are a pretty easy spot despite them taking so long for me to find! Further north, in the north of England and Scotland, they seem to be restricted to the coast. And if you want to see the caterpillars just keep an eye out for ragwort around July-through-September.
I would recommend trying to spot one. Moths are often not as kindly regarded as their butterfly brethren. Considered plainer, less beautiful and being associated with night, darkness, sometimes even withcraft, devilry or death. But they can be beautiful, intricately patterned, with cute faces and funny little habits and behaviours.
Get out there and enjoy some moths!
If you wish to get more involved or learn my about insects and invertebrates here are some links to The Royal Entomological Society and Insect Week resources.
Royal Entomological Society Website
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Insect Week Website
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Or you can read some of my other articles about insects and invertebrates below.
My Top Five UK Insects I’ve Seen: Introduction
An introduction to my top five insects, and a short look at why we need to see our insects differently.
Top Five Insects #5 – The Tawny Mining Bee (Andrena fulva)
Under-appreciated spring bee with a female who has incredible fox-red fur.
Top Five Insects #4 – The Rose Chafer (Cetonia aurata)
An otherworldly jewel of a beetle.
Top Five Insects #2 – The Thick-Legged Flower Beetle (Oedemera nobilis)
A charming iridescent green flower beetle, some of whom have thick thighs!
Top Five Insects #1 – The Ruby-Tailed Wasps (Chrysis sp. or Family Chrysididae)
Stunning little jewels that can teach us much about the diversity of wasps and insects.
Top Ten Hated (But Misunderstood) Animals – #1 – Wasps
A look at wasps in all their diverse beauty and glory and why they are important to us. A long-read.
The Wasp Tragedy – How Can We Help?
A few tips on how you can encourage wasps and other insect and invertebrate biodiversity in your home or garden.
Insects: The Savage Eden Before Your Eyes
A more in-depth look at my journey as I developed a relationship with insects and their role in our ecosystems.
Grown-Ups Guides: Hedge-Hunting for Bugs!
A short guide on how a total novice can get started appreciating the tiny wildlife in the undergrowth (safely)! Aimed at adults.
Human Bias and Animal Myth in Conservation
Not insect-specific but hugely relevant. Adapted from a twitter thread looking at how humans form ideas and relationships with the natural world.
We Lack Discipline 
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