7 APRIL 1939, Page 18

The Way of a Butterfly A curiosity of migration, in

the kingdom not of birds, but of butterflies, has been recorded in the West Indies. Hosts of butterflies—one was estimated at zo,000—have been watched on purposeful journeys between the islands and the main land of the Americas. One observer on the sea saw a battalion flying past in a precise direction, but at one point they checked, wavered, turned a sharp angle, and after crossing a short space, resumed their original direction. After a pause another body of the same species of butterfly was seen to perform exactly the same manoeuvre at the very same place. They, too, checked, turned the sharp angle, and, so far as could be judged, turned to the original point of the compass at much the same place. No one has yet found any sort of explanation either of such an odd similarity of tactics or of the general purpose of butterfly and moth migration. A very great deal has been discovered of recent years about the over- seas migrations of butterfly and moth ; and a singularly surprising story is unfolded in the reports (from lightships, light- houses and other sources) that are being pooled in the offices of an eminent entomologist at Rothamsted. But the multi- plication of facts has not so far, I think, even suggested a plausible explanation of the habit. It would seem in many cases to endanger rather than promote the preservation of the race, as ensured by the chrysalis, the egg and the hibernation.