27 AUGUST 1948, Page 14


AN ingenious explanation has been put forward for the scarcity of butterflies this summer. A letter to The Times points out that we have had two seasons remarkable for the absence of wasps, and wasps are the enemies of the parasites that have destroyed the butterfly cocoons. Quite certainly the great enemy of the butterfly is not the weather but the parasite. Years ago an effort was made to introduce butterflies into the London parks ; and I went round with the chief experimenters to inspect the cocoons suspended in a glass house in Battersea Park. We found that every single one had been eaten out by parasites, and the attempt to breed an urban race of butterflies had to be given up. It is a little hard to explain why the parasites flourish in the absence of their hosts. Probably they have a number of hosts. On several occasions in Charing Cross Gardens I have noticed the number of hover flies and such, and the complete absence of bees.