As with previous years, in 2009 people submitted Garden Moths Count results from
gardens all across the UK, and this year for the first time someone took part in
the Shetland Islands. What is more, the moth recorded there was a Silver Y, showing
just how far this migrant species can spread! Every spring and summer large numbers
of Silver Y moths migrate to Britain from Southern Europe, and even North Africa.
Once here they breed and their offspring add to the numbers moving northwards, though
new migrants also continue to arrive from southerly latitudes well into the autumn.
It is unlikely that any Silver Y moths or caterpillars survive the British winter,
and each year a fresh wave of migrants start the new population.
One of the moths we particularly focused on in this year of Darwin’s bicentenary
was the Peppered Moth, the famous example of natural selection. The survey results
provide a nice demonstration of the effect of air quality on the survival of the
two colour forms. Overall the pale speckled form greatly outnumbers the dark (melanic)
form, which were only 8% of the Peppered Moth sightings. In the 19th and earlier
20th centuries the melanic form had become far more common in towns and cities,
because it was better camouflaged on soot-blackened tree trunks, while the paler
form was still abundant in the countryside where tree trunks were clean and covered
in pale lichens. In more recent decades, legislation to reduce sooty air pollution
in urban areas has resulted in cleaner tree trunks on which the paler speckled form
is better camouflaged and so can survive in greater numbers, even in towns. It is
interesting to see on the map that not only is the melanic form less common now,
but the few that were found were mostly in urban gardens.
This year we also added the gorgeous Scarlet Tiger to the target list. This moth
seems to have been expanding its range, probably due to climate change, and we wanted
to see how far it had spread. The results were impressive. Compared to the last
published map of the Scarlet Tiger’s range (in 1983), the moth has become much more
widespread in its West Country heartland, with many additional sightings across
Dorset, Somerset and Gloucestershire. It has also become more common in the Home
Counties, especially around Oxford and has been rediscovered along the Sussex coast.
The sighting from the Lleyn Peninsular in North Wales is also exciting and shows
the northward spread of this beautiful moth in Wales.
To see the map for each species (and spot your own garden!) click on the moth’s
photo below.
(All records shown are as submitted by Garden Moths Count participants and have
not been subject to verification by Butterfly Conservation or County Moth Recorders.)