Silver Studded Blue, one of our rarest butterflies.
I recently posted some photos here and here of what I thought were Common Blue butterflies at Puttenham Common. Whilst editing the latest batch of pictures, I noticed a distinct sparkle of silver-blue iridescence on the spots on the wing undersides. This is the major distinguishing feature between the Common Blue (sadly not nearly as common as they used to be) and the rare Silver Studded Blue (Plebejus argus). There’s a good explanation of the differences here.
Silver Studded Blues are one of our rarest British butterflies, presumably due in large part to their favourite habitat of lowland heath becoming increasingly scarce. They have a fascinating symbiotic relationship with two species of black ants (usually with Lasius niger and – less commonly – on limestone with L. alienus). The young caterpillars emit a scent that attracts the ants, prompting them to tend to it and protect it from predators. When the final instar pupates, the ants carry the caterpillar into their nest and nurture it.
As is usually the case in nature, the reasons for this are not altruistic. The ants benefit from the relationship too; the caterpillars secrete a sugary, nectar-like substance from specially adapted glands, which the ants feed on. Even the pupal stage is able to do this, ensuring continuing care at their most vulnerable time. The ants take the late instar caterpillars or pupae into their nest chambers to tend to them, even protecting the newly emerged butterflies, who are covered in tasty droplets to give their guardians a final reward. There’s some interesting research here if you fancy learning a bit more about them.
Nature never ceases to amaze and enthrall me. Not only fascinating, but incredibly beautiful – these butterflies don’t fly far from their emergence sites, hence the clouds of bright blue fluttering above the heather. Just gorgeous. The shots of the pair on my hand are because my interfering cocker spaniel came racing back to me and disturbed them from the stem on which I was photographing them. They fluttered down onto the grass at the base of the heather, but the female was clearly not happy with this as she kept determinedly trying to crawl up higher, dragging the male behind her. I put my finger there and she crawled onto it; a few photos and I returned them to the stem that they’d been previously sitting on.