A new visitor to our site: The Swallowtail Butterfly

In autumn 2020, two plot holders reported discovering some amazing looking caterpillars happily munching away on plants on their plots. After a bit of research, it turned out that these caterpillars were in fact those of the Swallowtail Butterfly – one of our rarest and most spectacular butterflies, normally only found around the Norfolk Broads and in mainland Europe.

One of the caterpillars as found, feeding on a fennel plant

Giving nature a helping hand

To help his Swallowtail caterpillars reach adulthood, Stuart decided to bring the two caterpillars he saw indoors. Here he relates what he did:

“I found two Swallowtail butterfly caterpillars on some fennel on our Craven Vale allotment last October. I didn’t think they would survive the winter so decided to look after them until the Spring. Initially I put them on pieces of fennel in a white bucket as they were still feeding. The next stage was to introduce a couple of twigs to the bucket for them to attach to for when they were ready to change into a chrysalis, which they eventually did”.

Swallowtail Butterfly in crysalis form

“I then set up a home for them in a small butterfly tent in my allotment shed, to protect them from the worst of the winter. They overwintered there until May 2021 when I noticed one had changed to a darker colour. The next day it emerged as a beautiful Swallowtail butterfly. The moment I had been waiting for! – this was my very first view of a Swallowtail in the UK. The day it emerged was sunny with light winds so I felt happy releasing it.

The second chrysalis took another week to emerge and unfortunately the timing wasn’t great as the weather had taken a turn for the worse, being cold, windy and rainy. This went on for a few days and I started to worry about it surviving, as obviously it would need some form of food. The internet came to the rescue with information on force feeding. This sounds a terrible thing to do, but this was a do or die situation. So, I mixed up a solution of honey and water and put this in a shallow lid. The butterfly doesn’t know that this is food so it needs to be helped. I lightly held the butterfly with my thumb and forefinger with its wings closed, with the dish of honey mixture in front of it and gently unfurled its proboscis with a fine pointed tool, then dipped the proboscis in the fluid. To my surprise it worked, the butterfly started sucking up the liquid. For a few days I kept feeding twice a day until eventually the weather improved and I could release it. Poetically, it took off and soared up into the blue sky heading east towards the Downs until I could see it no more”.

Video showing how Stuart helped his second butterfly feed, before later releasing it back into the wild

If you have fennel on your plot, their food of choice, then keep a look out this autumn, you never know!

With big thanks to Craven Vale allotmenteer Stuart for his story and images.

Published by Nick

A plotholder on Craven Vale Allotment since 2010. I'm particularly proud of my expanding vineyard, which in a good year creates litres and litres of red and white wine! I love our site for the fabulous views over the sea and Downs, as well as the wealth of wildlife that can be found here. It really is a bit of countryside in the heart of the city. I feel very lucky to have my plot.

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