Beautiful but deadly

Beautiful but deadly

Marbled white by Wendy Carter

Discover the delights and hidden depths of this beautiful butterfly

As I was chatting to neighbours over our hedge yesterday, a marbled white flew past. I was delighted - the distinctive chequerboard pattern marked out one of my favourite butterflies.

I'm lucky enough that the garden backs onto a field. Although the field is frequently cut for silage or leased as a horse paddock, the edges are usually left unmown and long grass abounds - perfect for these butterflies. A brief sighting of a marbled white last year was put down to a passing individual looking for new habitat but to see one again this year was wonderful. 

The first time I saw a marbled white, I was hooked. It was lazily fluttering through a shrubbery next to a meadow.  I followed it for a short while, hoping to catch a photograph; a passer-by told me that I was wasting my time – marbled whites never settle.  I marvelled at the name.  I’d never even heard of it let alone ever seen one before.  I persevered and waited for it to finally settle on a flower long enough for me to snap a couple of pictures.

Marbled white butterfly (white and grey checked/marbled pattern) sitting with open wings on a grass stem by Wendy Carter

Marbled white by Wendy Carter

These delicate and captivating flutters are butterflies of grasslands.  Perhaps you're already aware that some butterfly and moth caterpillars can be rather fussy eaters? Marbled white caterpillars will happily munch away on a range of common grasses such as cock’s-foot, fescue and Yorkshire fog.  Maybe this is why the females drop their eggs onto the ground as they flick through the grass rather than carefully choosing somewhere to lay them.  Whatever the reason, when the larvae hatch they clamber into clumps of grass and chomp their way to pupation.  The adult butterflies emerge from the middle of June and are on the wing into August so now is a perfect time to catch sight of one.   

Sadly, England has lost around 97% of it wildflower-rich meadows but right here in Worcestershire we have about 20% of those that remain. As well as marbled whites, the flowers and grasses that grow here support all sorts of insects and the birds and mammals that prey on them. Meandering in meadows is a tricky business because there are so many delicate plants that can be trampled by our feet so to have marbled whites cling on in places like the field at the bottom of my garden is great news. Ideally, in order to spot marbled whites, you're looking for somewhere with lilac-coloured scabious, thistles and knapweed amongst long grasses - as well as meadows and grasslands, try disused railways, woodland rides and even road verges.

As I've already mentioned, marbled whites have a reputation for rarely sitting still so one of the best times to see one is in the morning when their wings are open and they’re soaking up the sun.  If you're out and about early, you'll need to 'get your eye in' - they roost about halfway down grass stems and can be surprisingly tricky to spot but once you've found one, you might well see others.

Could you believe that something so beautiful could be poisonous to birds?  Naturalist Miriam Rothschild always believed that such an eye-catching pattern must act as a warning to birds (see our aposematic video for more about this).  Shortly before her death in 2005, the development of chemical analysis proved her theory.  It appears that some caterpillars feast on grass that has been infected by ergot fungus; the toxins are stored in their bodies and the adults are subsequently dangerous enough to be left alone.