Lorraine Williamson
In Spain, we often hear about the dangers of the pine processionary caterpillar. But another species deserves attention this spring—the Festoon caterpillar.
I usually spot just one or two each year. However, earlier this week, I saw six in a single day. It’s prompted me to look deeper into what this striking creature is and whether it poses a threat. The answer? Potentially, yes.
What is the Festoon caterpillar?
The Festoon caterpillar is the larval stage of the Festoon moth (Zerynthia rumina), found mostly in southern Europe. With its patterned body and spiky appearance, it’s easy to mistake it for something harmless or even pretty. But appearances can be deceptive.
Like many brightly coloured caterpillars, the Festoon uses its looks as a warning. Its spines can cause skin irritation or allergic reactions. Though not as dangerous as the processionary, it can still be harmful—especially for pets or children who might pick one up.
Are they poisonous?
Festoon caterpillars feed on Aristolochia plants, which contain toxins. These toxins remain in the caterpillar’s body as a defence. While they don’t actively sting or bite, contact with their hairs can cause rashes or itching. In rare cases, more severe reactions can occur.
Dogs may suffer if they lick or eat one. The toxins may irritate their mouth, leading to drooling or swelling.
Can they be avoided?
Yes. Unlike processionary caterpillars, which move in long, noticeable lines, Festoon caterpillars are usually solitary. Look for them on low plants and in gardens, especially where Aristolochia species grow. Removing these plants can help reduce their presence.
You don’t need to use chemicals. Instead, wear gloves when gardening and discourage pets from sniffing unknown insects.
Should you be worried?
There’s no need for alarm, but awareness is important. The growing number I’ve personally seen suggests that conditions this year favour their spread. Perhaps it’s the mild winter or a shift in local flora. Either way, keep an eye out.
It’s also worth sharing your own sightings. Awareness can go a long way, especially in pet-owner groups or neighbourhood forums.
The Festoon caterpillar in Spain may not be widely known, but its numbers seem to be increasing. While not deadly, it is toxic and should be treated with caution. By knowing what to look for and keeping your pets safe, you can enjoy your time outdoors with fewer surprises.