Male vs. female

Some species of butterflies are known for sexual dimorphism. The different appearance of male and female individuals are most commonly visible on the adult butterflies. However, since the chrysalis of some butterflies turns transparent before the adult hatches, the differences can become visible already.

During winter 2015/2016 I kept chrysalises from the Large White (Pieris brassicae) and the Orange Tip (Anthocharis cardamines). Both species have sexual dimorphism, especially the Orange Tip where the orange color is only present on the male’s wings. In case of the Large White the black dots are only present on the female’s wings.

I managed to get some photos from chrysalises of both sexes prior to hatching. Here’s how easy the gender can be identified (once the pupa turns transparent). The photos of the adult Orange Tips are from the wild but added as a further reference to show the difference between female and male.

Migrant mastering winter

People say the Large white (Pieris brassicae) can’t normally survive the cold winters in Finland. Commonly, the butterflies migrate north in late summer and potentially breed after arrival. Nevertheless, in late 2015 I managed to find masses of caterpillars and took exactly 27 of them home for raising. In late spring 2016, every single one hatched.

I kept about half of the overwintering chrysalises in the fridge. The rest spent the entire winter on a balcony in the shadow, exposed to temperatures as cold as -25 degrees Celsius. The chrysalises from the fridge were also placed on the balcony in spring to get them hatch at the same time when the conditions are right.

My first surprise was that the caterpillars did not have parasites at all. The second surprise, of course, was to see the adult butterflies hatching. This are great results, proving the species can handle the conditions in the North and is able to overwinter locally.

Species check at the farm

Today, I wanted to take a different approach searching for caterpillars and butterflies. Instead of searching for a particular species I selected a small location. I then spent about an hour at that location, the Haltiala farm in Helsinki, trying to spot as many species as possible.

No rare species today, but it was a good day and it was great to see that the ordinary butterfly species do very well at the moment. What I found was young caterpillars of the Elephant hawk-moth (Deilephila elpenor), lots of caterpillars of the Red admiral (Vanessa atalanta), caterpillars of the Small tortoiseshell (Aglais urticae) in almost all instars, Large whites (Pieris brassicae) that most likely migrated to Finland recently and of course, European peacocks (Aglais io).

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.