The silver Y moth

It isn’t often that a moth makes it onto the local, let alone international, news but on the July 10 at football’s Euro 2016 final a “plague of moths descended” on Paris and one landed on the face of the injured Cristiano Ronaldo. This was enough to send the media world into a frenzy with a wide range of inaccurate comments and sensationalist headlines.

The moth in question was the ‘silver Y moth’, Autographa gamma. Its characteristic trade-mark is the metallic, silver Y-shaped mark on each wing. The background colour of this moth is variable from pale marble through to quite dark brown, in rare examples almost black. Even the size is quite variable, its forewing length varying from 13 to 21 mm.

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The silver Y and migration

The size and colour of the silver Y moth depend to some degree on where the creature lived as a larva. This is a migrant species, it is generally unable to survive in the UK over winter. Instead it migrates here from North Africa and southern Europe each spring. The silver Y is a strong flyer, regularly recorded in Iceland and Greenland as well as Scandinavia. The early summer migrants to the UK are mostly of the pale form.

Those moths which make it to the UK in spring might remain here to breed and in some years two generations of silver Y moths can be born here. The moths born in cooler climates, such as in the UK, tend to be darker in colour.

Their pattern of migration doesn’t end in summer. In the autumn the silver Y moths born in the UK head south to find warmer weather in the countries where their parents or grandparents were born. This migratory pattern is far from accidental, it is thought that individual moths can tell north from south and are even able to assess the wind direction before choosing suitable conditions in which to achieve their intended migration.

Every few years a mass movement of silver Y moths occurs with maybe a quarter of a billion of them arriving in the UK. These moths can quadruple in number over the summer to create a southerly autumnal migration of about a billion moths.

Silver Y moths in the UK

Clearly, because of the way in which they migrate, silver Y moths are always going to be commoner in the southern half of Britain with coastal areas having the lion’s share but they can be found across the length and breadth of the country.

Their larval food plants include bedstraw, clover, nettle, peas and beans so in years when there is a lot of them they can be regarded as an agricultural pest. Their search for nectar takes them into a wide range of habitats including gardens and they can be seen in the UK from May to September when they begin their reverse migration.

Observing silver Ys

I sometimes set a moth trap in my garden. This consists of a very bright light (mercury vapour) and a box with sides sloping down into a narrow entrance. Moths are attracted to the light and some slip down into the box finding it difficult to get out again. Within the box I put open egg boxes so they have somewhere to hide and rest until the morning when I can inspect my catch. The moths are not harmed by this process and it provides a fascinating insight into the nocturnal activity in the garden. Visit Butterfly Conservation for their guide to building or buying moth traps.

On many occasions I have caught silver Y moths in my trap because they are attracted to bright lights and this is where it all went wrong in Paris for the Euro 2016 finals. For some reason officials decided to leave the stadium lights through the night before the final took place. This acted like a giant moth trap, attracting moths in from miles around.

Looking on the bright side, if you will excuse the pun, it was good that the final was staged in July and not September when there could be four times as many of these silver stars!

Find out about the different moths you might see in your garden