Nettles, caterpillars and butterflies

Posted: Thursday 5 June 2014
by Kate Bradbury

There’s a clump of nettles growing next to the communal shed on the allotment. I clocked it early on as somewhere to keep an eye out for caterpillars.

Caterpillars on nettles

There’s a clump of nettles growing next to the communal shed on the allotment. It’s a small patch but it gets sun for most of the day – I clocked it early on as somewhere to keep an eye out for caterpillars.

I’ve visited the nettle patch periodically over the last few weeks and found nothing, although I did see the odd small tortoiseshell fluttering by sometimes. Then I forgot all about it – I had weeding to do.

But last weekend I stopped at the nettle patch again; I wanted to harvest some leaves to make a nitrogen-rich nettle feed for my crops. But the plants were looking sickly, and they were covered in caterpillars.

The nettles had been sprayed with weedkiller (all communal areas on the allotment are). The yellowing leaves and stalks were not going to help me feed my plants, but neither would they support in excess of 100 hungry caterpillars – some of which already looked half-dead. So I did what any self-respecting wildlife-obsessed gardener would do: forgetting all about the nettle feed, I gathered up the caterpillars and took them home.

At home I have a modest nettle patch, where I deposited half the caterpillars. They're small tortoiseshells and/or peacocks, two batches of early instar larvae and another of final instar larvae. ‘Instar’ refers to the stage of the caterpillar’s growth –as they grow they shed their skin, like a snake, and each stage between moults is referred to as an instar. Most butterfly caterpillars have four or five instars before pupating. Early instar caterpillars are small, and final instar caterpillars are large and chunky – often bearing no resemblance to their former selves.

I popped the remaining caterpillars in an ice cream tub, which I’m keeping in my bedroom.

Three final instar small tortoiseshell caterpillars made it to the ice cream tub. These pupated within a day and are now suspended on sticks from my bookcase. I raised some small tortoiseshells from caterpillars last year and it took just eight days for the adults to emerge from their chrysalides – this means I could have butterflies by Tuesday. The rest are busy eating freshly harvested nettles from the local park, and have some way to go before they pupate.

Peacock and small tortoiseshell caterpillars have similar habits. On emerging from their eggs they build a communal web, which they shelter under when not feeding. As they grow they shed their skins, move to new plants and build new webs, leaving a trail of webs, shed larval skins and droppings behind.

They’re doing just that in the ice cream tub. I’ve tried to create as realistic conditions as possible – I arrange their daily meal of fresh nettles so they are standing tall, and the caterpillars spin webs on the tips and gather together inside them. I counted 44 of the gorgeous things, which is lovely now when they’re so small, but I might need to rethink their living arrangements as they mature. As they grow and become more independent I may find fresh nettle patches for them to live on, or I might split the group in two, using a second ice cream tub. I’ll also place sticks in the tub so they have something to climb up and pupate on. This is very important for butterflies – if they pupate on the ground they may have problems emerging from their chrysalis and may not develop their wings properly.

Fingers crossed, in about three weeks’ time I will have successfully reared my caterpillars from tiny babies to beautiful butterflies. Imagine waking up to finding all 44 emerging from their chrysalides at the same time? It’s the stuff of dreams. And hopefully a happy ending for lives nearly cut short by weedkiller.

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Talkback: Nettles, caterpillars and butterflies
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oldchippy 05/06/2014 at 19:38

Kate you are a romantic softie. who else would love caterpillars.

philippa smith2 05/06/2014 at 19:40

A clump of nettles in a pot so they don't spread is ideal for any wildlife friendly garden.......easy enough if you don't let them seed.........highly recommmended

gardenning granny 05/06/2014 at 19:41

the righrt ones are worth looking after - they give us the most beautiful butterflies

I have many butterfly friendly plants in the garden - just as important aas looking after the birds

maria 3 05/06/2014 at 19:52

Lovely story, well done to you!

Russell Tilling 07/06/2014 at 09:13

Re gardening grannies point about looking after butterflies (& I take it insects generally) as well as birds.
I am thinking that feeding birds all year round will encourage a larger population of birds than my - and my neighbours' - gardens will naturally support. This larger population will also impact insects and caterpillars more by feeding on them!
Therefore I'm considering reducing or stopping feeding the birds - in the summer at least - so they don't overbreed and eat all the caterpillars, etc!
I have plenty of grasses with seed as well as any in the feeders

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