A midsummer’s butterfly ballet
Reveals a fascinating world of wildlife that we often overlook.
Triangles of tin foil on the breeze, the butterflies flash and flare, the silver wash that gives them their name catching both the eye and sun. This is not a random tumbling flight: it has a pattern, driven by a purpose. It is a midsummer’s aerial ballet, a dance of seduction and intoxicating perfume.
Among the largest British butterflies, silver-washed fritillaries are spectacular even on their own, while perched relatively still on a favourite bramble bloom. But to see a pair of them at their sexual peak, going through the moves of securing a future generation, is something to behold.
Sadly, this sight is today confined to southern England, in wildflower-rich woodland rides at the height of summer. To be more specific, your best chance is from around noon until 3pm: females tend to be more active in the morning and males in the afternoon, with a period of overlap between the two.
The male fritillaries patrol with a zig-zag flight very different to their usual frivolous flutterings when seeking the sugars to fuel their lust. If you see this, keep watching. When a male approaches a virgin, ripe female, he casts tight circles about her. Should she be up for it, she leads him on a merry dance. What now unfolds clearly has form, though it’s often difficult to work out as the human eye sometimes struggles to keep up. But in a good view, you’ll witness an elaborate courtship.
The female butterfly flies straight, dragging the male’s ardour along on an invisible plume of scent particles; pheromones that she drips from glands at the tip of her abdomen. His response is to follow close, almost tailgating her irresistible odour. Next he engages in a loopthe-loop flight, flying under and above her straight trajectory. Slow the action down and you would see him close his wings and stoop, an act that allows him to catch up, briefly overtake by a length, then rudely rise up in front of her, barging into her path and causing her to stall.
In that apparent clumsy, bumpy interjection the male turns almost upside-down, with the female’s antennae purposely close to his androconia, or sex brands. Compare the surface of his wings with hers and the p attern is clearly different. He h has four stripes per forewing, w where she has none. These are his h androconia.
Zoom in and you’re now en ntering a hidden world of microscopic m function and at tomic smell. For the markings ar re more than just the regular p igmented scales found on the re est of the wing – they are raised an nd textured, like small brushes. Their T job is to provide a large su urface area to disseminate p erfume made by pouches at th he scales’ base. The heavy scent molecules m are wafted in her face. Seduced by smell The T looping courtship is re epeated again and again, h him showering her with the p erfume of his intent, until she ei ither declines his offer and fl lies off, or settles – in which ca ase there follows a more in ntimate ritual. There is more fl lapping and fanning, as well as s a face-to-face bow where he tr raps her between his forewings an nd forces her antennae, the or rgans by which these insects p erceive pheromones, onto his an ndroconial organs. A lengthy mating m of a couple of hours en nsues, a time worthy of the in nvestment of the dance.