Ray Colliers Wildlife in the North – Butterflies (Part 2)

Large White ButterflyLast week’s “Wildlife in the North”  painted a dismal picture of butterflies in the Highlands during  this last summer.  Then in the last week of September there was a sudden flurry of butterflies in gardens in and around Inverness and elsewhere  as if going a sense of optimism for butterflies in 2014.   The main butterflies were the red admirals and peacocks and one afternoon I counted eight red admirals on the Sedums and Buddleias. Worryingly there were no small tortoiseshells   which may indicate that the mysterious, marked decline of this once very common butterfly is still very much cause for concern.   Two other butterflies were also present,  the speckled wood and the large white.  The speckled wood would have been offspring from a second brood and this is a butterfly that is now spreading  annually to new parts of the north.

The large white, which many people regard as one  of the dreaded so called “cabbage whites”, is a large and  fascinating   butterfly in its own right.   As for its size,  the photograph I took of a Buddleia on the last day of September shows a red admiral and large white.  This indicates that the red admiral, often regarded as one of the largest of the UK butterflies, is just about the same size as the large white.   Many large whites are resident in the UK all the year round and hibernating chrysalises have regularly been found as far north as Orkney.    However, what is often not realised is that the large white is a very successful migrant to us from northern Europe and  further north.  We may realise that  there are well known migrants such as small tortoiseshells,  red admirals, painted ladies and even the much rarer clouded yellows.  The large white can match their exploits and in many cases surpass them. Some years the migrant large whites  run not into thousand but sometimes even millions.  There are sighting of vast numbers alighting on ships and even on the sea.  One spectacular migration I was lucky enough to see was off the  east coast.  As the large whites came ashore, obviously tired, the gulls were waiting  for them and snapping them up. When the migration was over the shoreline was white with the discarded wings of the butterflies.

Whilst this may be the fascinating side of the large white there is no doubt that it can cause quiet serious damage to Brassicas, including cabbages, kale and Brussels sprouts.  The caterpillars can wreak havoc and left alone they can clear a large area of garden very quickly.   This is why it so often called the “cabbage white” and dreaded by gardener and farmer alike.  However, one of the quirks of the large white is that it has a defence mechanism against predators such as birds.  Whilst to birds and small mammals the clusters of caterpillars  may seem attractive there is a hidden menace.    Whilst feeding on the leaves of various plants the caterpillars accumulate poisonous oils that will deter most predators.

The problem is that when  we think of large whites and  their effect on the cabbages we often include the  small and green-veined whites.   The small white does indeed feed on cabbages but their numbers are smaller  and they rarely achieve the same sort of damage as the large white.  In the case of the green-veined  white, the caterpillars do not feed on cabbages and therefore should  not be included in the “cabbage whites”.

Tags: