We meet with analogous facts in butterflies. Thus _Lycaena agestis_ not only presents seasonal variations, (A) and (B); but while (A) and (B) are respectively the winter and summer forms in Germany, (B) and (C) are the corresponding forms in Italy. Therefore, (B) is in Germany the summer form, and in Italy the winter form--the German winter form (A) being absent in Italy, while the Italian summer form (C) is absent in Germany. Probably these facts are due to differences of temperature in the two countries, for experiments have shown that when pupae of sundry species of moths and butterflies are exposed to different degrees of temperature, the most wonderful changes of colour may result in the insects which emerge. The remarkable experiments of Dorfmeister and Weismann in relation to this subject are well known. More recently Mr. Merrifield has added to their facts, and concludes that the action of cold upon the pupae--and also, apparently, upon the larvae--has a tendency to produce dark hues in the perfect insect[110]. [110] _Trans. Entom. Soc._ 1889, part i. p. 79 _et seq._ But, passing now from such facts of climatic variations over wide areas to similar facts within small areas, in an important _Memoir on the Cave Fauna of North America_, published a few years ago by the American Academy of Sciences, it is stated:-- "As regards change of colour, we do not recall an exception to the general rule that all cave animals are either colourless or nearly white, or, as in the case of Arachnida and Insects, much paler than their out-of-door relatives."