A White Invasion Everyone must have noticed the exceptional number
of white butterflies this summer. Those who fear for the ruin of their cabbages by the greedy progeny may gratefully remember that these are the only kind that do any harm to anyone. They are not numerous on the scale described some years ago by Miss Turner, who likened their migrating swarms in Norfolk to a dense snow-storm ; but they are as constant a spectacle in the garden as the annual flowers. They have a great gift of survival ; but how they serve their race by mass-migration in autumn is still a query that has found no answer. Any informa- tion on the migration of any butterfly will be welcomed by Dr. Williams, of Rothamsted, Herts. In my garden the chief sufferer from caterpillar greed has been the groundsel. Every other plant has been gnawed to a skeleton by the yellow-banded grub that particularly affects this weed.
It is odd that the morning after the above was written I read an account of the hordes of white butterflies that had landed on the South Coast. It was suggested that the lack of food in Northern France was the cause. It may be so ; but the more usual line of migration is across the North Sea, not the Channel.
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