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Butterfly Blitz in Prospect

Bird On! News
13th August 1996

They are not birds but most people interested in birds are also interest in butterflies and moths - especially migrants. Britain is due for an exceptional explosion of butterflies and moths.

In early June we experienced an enormous invasion of Painted Lady butterflies and Silver-Y moths. There were more involved than in any invasion for 30 years. It was also very exceptional for it happen as early as the first few days of June. Invasions usually happen in late July or August and are made up of butterflies and moths bred in France.

This year we are poised for an extra huge invasion of homegrown butterflies and moths resulting from millions and millions of eggs laid in southern England early in June. These eggs hatched, the caterpillars thrived in the good weather and they have pupated soon to emerge as adults. The Painted Ladies have used thistles as their food plant. Dr Martin Warren of the charity Butterfly Conservation said that in Dorset he usually has to look very hard on the thistles to find any Painted Lady caterpillars. This year every thistle is covered in them and he is looking forward to an explosion of beautiful butterflies in the next few days. They will, inevitable, fly North over the whole of Britain and try to rear another brood.

The Silver-Y Moths take their name from a Y-shaped silver mark on the forewing of quite a big brown and furry moth. They fly by day as well as night. They are sometimes pests in field crops in Southern Europe. This year, for the first time in living memory, they have invaded crops in this country. The crop is spring-sown oil-seed rape and the moths escaped spraying because there were so few pollen beetles around in spring. Some crops along the South Coast have been devastated and there are countless millions of pupae just about to hatch. They too will make their way North like the Painted Ladies.

Roy Taylor of the Royal Society for the Protection of Birds was working on the local song birds near Chichester. He could not understand what was happening as clouds of Starling and other birds like thrushes, warblers and Yellowhammers were piling into the rape fields. In earlier years they had shown no interest so he went into the crop and found an extraordinary phenomenon. The birds were feasting on the pale silk cocoons containing the Silver-Y pupae. There were thousands of Starling but so many pupae are in the fields that lots will escape and there will be an amazing hatch very soon.

The butterflies and moths are very attracted to some garden plants. Buddleia bushes, in bloom, will be covered with them and so too will the pink sedum and the big yellow flowers of the Evening Primrose. Fine and windless days will be the best time to see the Painted Ladies who will be joined by the other local butterflies. The evening will see most activity from the Silver-Y moths.

If the weather stays warm and these lepidoptera will survive for several weeks. There is also likely to be an invasion from the Continent of further Painted Ladies and Silver-Ys but they will also be joined by all sorts of other species. Red Admirals will probably figure prominently and there may be clouds of whites as well. The real excitement will be if there is an invasion of Clouded Yellows - this happened memorably in 1947. That year was also fantastic for the Hummingbird Hawkmoth invasion. These moths are day fliers and very noticeable. Already migrants like Deaths Head Hawkmoth have been spotted too. If the weather stays fine to the end of August and early September may see a big return migration Southwards of surviving butterflies and moths.

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