Country diary: the ‘lady of the house’ has been left to her fate
Wenlock Edge, Shropshire: This battered scarlet tiger moth has seen off predators and survived injury, but its defence strategies are failing T he moth looks moth-eaten. Its magpie white splashes on iridescent black forewings and its scarlet hindwings are distressed. It flutters erratically, unable to lift off from wet grass. Coaxed on to a leaf and transferred to the safety of a hedge, it soon struggles back to the same spot on the ground, as if awaiting its doom. Linnaeus named the scarlet tiger moth Callimorpha dominula , the lady of the house. This lady looks as if something terrible has happened to her and she is abandoned to her fate a long way from home. Scarlet tiger moths are usually flyers of marshy places, fens, riverbanks and coastal wetlands, but they are sometimes found in gardens and along ditches. Their principal larval foodplant is comfrey and the caterpillars also feed on nettle, hemp agrimony and meadowsweet. They fly by day and by night, and maybe this ability and widening choice of habitats and food plants is helping them adapt to climate change and extend their range northwards from south-west England and Wales. It has certainly been suitably damp for them recently, but the adult moth only lasts a fortnight and, reaching the end of its flying period, is exhausted. This ones wing damage may have been caused by birds or bats, and its sophisticated defence strategies are failing. The distinctive colours of tiger moths are aposematic, a warning to predators of toxicity; the hairy white and yellow caterpillars contain neurotoxins (best to leave them alone). However, warning colours do not work in the dark and so these moths have developed an acoustic signal of alarm snaps that advertise their unpalatability and a biosonar jamming system that disrupts bats ultrasound. Scarlet tiger moths can also be yellow, and the variability of colours and patterns in their populations has led to decades of research about whether evolution occurs principally through natural selection or from a neutral process called genetic drift fluctuations in gene variants passed on by lucky individuals rather than healthier, better individuals. Perhaps, despite being battered, this burlesque lady of the house is luckier than other scarlet tigers; maybe surviving this long against predators and the pervading weirdness is a sign of being better, but it feels like the tragedy of heroism.