This section is from the book "The Gardener's Monthly And Horticulturist V22", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Psyche for January contains a highly interesting paper by W. H. Edwards on the effect of cold on insects. The chrysalids of Papilio ajax were frozen in a temperature of about 32°, and kept in the ice for many days. The ones exposed but fifteen minutes emerged on the forty-third day after exposure, while those exposed nineteen hours did not appear till the ninety-sixth day, and the proportions were just about the same in the cases between the fifteen minutes and the nineteen hours; concluding, Mr. Edwards says: " That the effect of cold is not simply to precipitate the emerging of the winter form, making the butterfly which would naturally leave its chrysalis in the succeeding spring to emerge in the season in which it fed as a caterpillar, is evident from the fact that the shape is always that of the summer form, while the markings are of the winter form. Those chrysalids which go over the winter, on the other hand, do not have the summer form, but the winter, and the markings agreeing thereto, just as in examples in nature.
On these the cold has produced no effect whatever".