Dispersal of Butterflies and other Insects

Abstract

THE letter of Mr. Robert Adkin in the issue of NATURE of September 26, on the vertical upward flight of moths from the Downs near Walmer, supplies one of the desiderata required to confirm the view indicated in Mr. Felt's article in NATURE of September 5 that the upper air-currents may play an important part in the distribution of flying insects. I have myself long expected that the dispersal of insects would ultimately attract the attention of the meteorologist, and Dr. Simpson's British Association address, which immediately precedes Mr. Felt's article, reads appositely beside Mr. Felt's appeal for the aid of convectional currents arising from heated surfaces in assisting insects to gain the upper air-strata. But in this connexion we must not forget that mountaineers have long exercised their brains over the problem of insects on high mountain tops. Whymper in particular, in his work on the equatorial Andes, dealt with this subject, and he quotes Humboldt and Bonpland as showing that insects are transported into the upper regions of the atmosphere (16,000 to 19,000 feet), and adds that the transportation of insects by ascending air-currents has occasionally been observed in operation. One such set of observations is noted by Mr. Felt when he writes, “Collectors on some of the high mountains, such as Mount Washington, have taken insects which are distinctly southern or south-western in habitat, probably carried there by the upper air-currents and dropped upon these cooler mountain tops”.