It is a well known fact that the flight of moths and some other insects is affected by barometric pressure, but it is not well known how this phenomenon affects other insect activity. In a study of the ecology of insects in vegetable gardens at Brandon, Man., in 1948, the relationship of barometric pressure to insect activity was recorded.

It was noted in the field that the imported cabbageworm adults behaved differently under varying weather conditions. During warm, clear days they did little but move about freely and feed, but on days that were overcast, particularly preceding rain, they became active about the plants and appeared to be engaged mainly in egg laying.