GREAT SEX DIFFERENCES

THISTLE BUTTERFLY

Another group of butterflies which are nobly represented in North America are the Fritillaries, belonging to the genera Argynnis and Brenthis. A group of these insects is shown in one of the plates. The reader will observe how great a difference there is between the males and the females, especially of Argynnis Diana. When the sexes thus differ they are said to be “sexually dimorphic.” There are other kinds of dimorphism. When butterflies have several broods it has been observed that those of the spring brood differ in form and markings from those of the summer brood, and again from those which come forth in the fall of the year. Such species are said to be “seasonally dimorphic.” In the tropics we recognize what are known as “dry season forms” and “rainy season forms,” which are often very unlike each other. Sexual dimorphism is not so pronounced in all species of the genus Argynnis as it is in A. Diana. The Fritillaries have their metropolis in North America, but are also well represented in Asia, Europe, and to some degree in Africa and in South America. In the latter continent the species occur among the cool Andean regions and in the far south, in Patagonia. It is a curious fact that on the flanks of Mounts Kenia and Kilimanjaro, in Africa, separated by thousands of miles from their congeners, there are species of this group of butterflies. How did they get there? The geologist maybe can answer.

THE COMMA

America is rich in species belonging to the family of the Hesperiidæ or “Skippers.” They are well named, as anyone who has watched them skipping and gamboling among the flowers can testify. They seem to be in some respects intermediate between the other butterflies and the moths.

An adequate account of the breeding of butterflies and of the methods of preserving them for study and display would require another article. I will then, at this time, simply refer the curious to the books already written about these things, and, if any of The Mentor readers are tempted to find the secret of eternal youth, by becoming entomologists, they will discover that every library of any size has in it today copies of the books they need to guide them. That was not the case forty years ago.

NETTLE TORTOISE SHELL