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. Meet the silver-washed fritillary
What is a silver-washed fritillary?
The silver washed fritillary is one of Britain's largest butterflies, and one of the most beautiful
How big is the silver-washed fritillary?
Its wingspan is a pretty impressive 72-76mm
Why are they named silver-washed?
Its their silver streaks on their underside that give them their name
Where do silver-washed fritillaries live?
Sadly, the sight of them today is confined to southern England, in wildflower-rich woodland rides at the height of summer.
When is the best time to see them?
your best chance of seeing them 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.
What do silver-washed fritillaries eat?
They are particularly partial to feed on bramble and flowers in sunny glades, while their caterpillars love violets, particularly common dog-violet.
How do silver washed fritillary mate and reproduce?
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.
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 loop-the-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 pattern is clearly different. He has four stripes per forewing, where she has none. These are his androconia.
Zoom in and you’re now entering a hidden world of microscopic function and atomic smell. For the markings are more than just the regular pigmented scales found on the rest of the wing – they are raised and textured, like small brushes. Their job is to provide a large surface area to disseminate perfume made by pouches at the scales’ base. The heavy scent molecules are wafted in her face.
The looping courtship is repeated again and again, him showering her with the perfume of his intent, until she either declines his offer and flies off, or settles – in which case there follows a more intimate ritual. There is more flapping and fanning, as well as a face-to-face bow where he traps her between his forewings and forces her antennae, the organs by which these insects perceive pheromones, onto his androconial organs. A lengthy mating of a couple of hours ensues, a time worthy of the investment of the dance.
Main image: Silver-washed fritillary © Getty Images
