Sequins are a popular way to bring ethereal pizzazz to an outfit. But back before synthetic bling was mass produced in every shade of fabulous, the source of such dazzle could be ethically dubious but more iridescent still. For Victorian fashionistas a statement collar or cape might have been adorned with the wingcases of thousands of tansy beetles.
These days, the entire British population of Chrysolina graminis could probably all fit on one dazzling atrocity of a garment. Of these precious few beetles, almost all now live on the flood meadows of the river Ouse, either side of York.
There are large clumps of tansy (Tanacetum vulgare) here, its compact flowers looking like bunches of gold buttons. When crushed, the plant’s foliage is so bitterly aromatic it makes a serviceable insect repellent. To tansy beetles, though, this is the scent of home.
It takes my eyes a while to adjust to the matrix of feathery leaves and reddish stems, but there’s no mistaking a tansy beetle when it clambers into view. It is the size of my little fingernail, bulbous and goblin green with auroras of cherry bronze and gold glowing along its curved flanks.
Mid-August marks a generational changing of the guard. This year’s parents have all but died off, and early in July their odd brown grubs, slug-like in colour and form, retreated into the mud to undergo a stunning transformation. They are emerging now as flawless adults.
Photograph: Alamy
These summer individuals can fly but rarely do so, and their pedestrian trundle and cheerily waving antennae make an enchantingly easy watch. Close up, you can see the carapace is delicately pitted. The pit pattern distinguishes this gem from the more common but less spectacularly colourful mint leaf beetle, Chrysolina herbacea.
Come autumn they’ll be gone, self-interred in the Ouse ooze, to wait out winter shortages of food and excesses of water while their wings resorb and reproductive organs develop.
This flood-prone stretch of river seems an unlikely home for such a sedentary creature. But saturated ground might just be a blessing, by creating a challenging spot for moles and other predators likely to target the beetles during their underground metamorphosis.
