Beautiful pest – The Large White

Some butterflies are not only seen as beautiful creatures. While the caterpillars of most species enjoy plants growing in the wild others have a preference for cultivated plants. The Large White (Pieris brassicae) is often referred to as being a pest, causing severe damage in cultures and gardens.

Usually, the Large White is kept in balance by natural parasites, especially the White Butterfly Parasite (Cotesia glomerata). I recall raising caterpillars as a small boy when usually most of them died due to these wasps. That was in Switzerland, where the species is common. It took a while to sight adult butterflies up north in Finland. Pretty soon after seeing them fly I also humbled into caterpillars, lots of them.

I grabbed a hand full of caterpillars home for raising. It will be nice to get them over winter by keeping the chrysalises in the fridge. Normally, the Large White is known as a migrating species in Scandinavia. Most winters are too harsh for the butterfly to survive, and it takes until late summer again for the next generation to arrive from South.

An interesting observation while raising the caterpillars this time was that none of them were affected by parasites. All 27 caterpillars made it to pupae, and they’re now hibernating in the artificial, mild winter of our fridge. It felt like the butterfly’s enemy, the White Butterfly Parasite, didn’t make it at all to Finland that year.

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