Last week, I witnessed a wondrous and slightly horrifying spectacle of nature.
I was admiring a swallowtail, Britain’s largest native butterfly, as it jinked over a waterway on the Norfolk Broads. Suddenly, an emperor dragonfly cruised in and grabbed the butterfly. There was a mid-air tussle for five seconds, before the iridescent blue dragonfly dropped into the reed bed with its prize.
I cautiously parted the reeds to see what happened next. The dragonfly had vanished with its meal, leaving one quarter of pristine swallowtail wing.
Of course, like every insect, butterflies are food, just as the emperor makes a decent meal for the dashing hobbies that hunt them over the Broads.
There may be relatively few butterfly species compared with moths because day-flying is a hazardous evolutionary decision. Many butterflies have eye-spots that deter predators such as birds or lure them into attacking the outer edges of the butterfly’s wings, which the insect can do without.
Seeing this swallowtail devoured made me wonder why every individual is not immediately grabbed by the many big dragonflies that share their airspace. Was this individual unlucky or naive? It was freshly emerged, so probably the latter. But clearly a swallowtail’s apparently carefree jinking flight is a – mostly successful – dodge to survive in a hostile world.