Saturday, May 5, 2012
What happens when a raindrop, travelling at terminal velocity, hits a butterfly .....?
I've never seen an insect actually hit by a raindrop but I did once read an eyewitness account (of dubious reliability) of such a collision with a bumblebee in flight, which supposedly killed the bee. It came to mind yesterday as a dark rain cloud slid over the sun while I was photographing this newly-minted female orange tip butterfly visiting bluebells.
Almost immediately the butterfly folded its wings as completely as possible, assumed a vertical position on a bluebell infloresence and even aligned its antennae tightly in line with its body axis - all of which presented the smallest possible target for a falling raindrop. I wonder if this instinctive behaviour is triggered by the sudden drop in light level and temperature that's characteristic of an approaching shower on a spring day? Many insects crawl away under leaves during rain showers but orange tips always seem to roost in the open. I've often found dew-covered specimens early in the morning.
As soon as the sudden and very heavy shower had passed I went out to take a look and found the butterfly unharmed..... hard to believe that it hadn't been knocked off its perch by the downpour!