Peppered moths
During the day our garden is alive with insects. The brambles, rampant once again despite my attempts to eradicate them, have their flowers covered with bumblebees and hoverflies with an occasional butterfly.
The same is true of the cotoneasters which, like the brambles, seem intent on spreading and taking over but with their tiny pink flowers irresistibly attractive to the bees.
Once darkness falls, the night shift takes over but, with the clear skies and dropping night time temperatures of the recent heat wave, conditions for night flying insects have not been ideal. Moths prefer cloudy, damp nights and I have been struck by the small numbers attracted to lighted windows while my moth trap, with its ultraviolet strip lights, has not attracted more than ten species on any recent night.
I do like to catch the big, spectacular moths and, among those I have caught in the last few weeks, two have stood out, poplar hawk moths with three inch wing spans and peppered moths, smaller at two inches, white, lined and speckled with black (pictured is a male with feathered antennae used to detect the scent of females at a distance). Against green vegetation they stand out but on the lichen covered tree trunks and boughs where they rest during the day they are almost invisible against their background.
Peppered moths are famous for the speed with which they adapted to the soot and air pollution of the 19th century industrial revolution which killed off lichen and turned trees and walls black.
There is a black form, caused by a genetic mutation, and under normal circumstances these stand out against pale backgrounds making them more likely to be eaten by birds and therefore less likely to breed.
However, during the Industrial Revolution, this form came into its own when it was the pale form that became obvious to predators. The first black peppered moth was recorded in Manchester in 1848 but within 50 years 98% of those in the city were black. With controls to reduce air pollution the trend has been reversed so that most peppered moths are again pale, natural selection in action.
Unfortunately, the ability of the moth to adapt has not extended to the loss of habitat and the increased use of pesticides ravaging the insect populations in the wider countryside and in urban gardens. The peppered moth population has fallen by two thirds in the last thirty years. In many parts of the country, including Wharfedale, where wild flowers and their attendant insects have been eliminated by intensive farming, gardens may be the last refuges for the insect life on which plant pollination and the rest of the animal food chain depends.
Denis O’Connor
