Many students of American butterflies have occasionally mentioned the fact that certain species seem to give off a distinct scent which has frequently been spoken of as a pleasing fragrance, suggesting sandalwood or some other aromatic odor. The general subject as exemplified by butterflies of other lands has been studied for many years by Fritz Mueller; and certain English entomologists have paid considerable attention to it. A translation of the Mueller publications and an excellent summary of our present knowledge of the subject is published in Dr. Longstaff's book on butterfly hunting. The odors given off by butterflies are divided into two principal kinds, namely: first, those which are repulsive to the senses of man, and evidently for the purpose of protecting the butterflies from birds and other vertebrate enemies--these are found in both sexes; second, those which are evidently for the purpose of sexual attraction and confined to the male butterflies--these scents are usually attractive to the senses of man. [Illustration: Androconia from wings of male butterflies] The aromatic scents of the second group are generally produced by means of certain scales or hairs of many curious forms, which are scattered over the surface of the wings or are placed within certain special pockets, generally near the borders of the wings. These scales or hairs are called androconia. Some of them much magnified are represented in the picture above. Our knowledge of the scents given off by American butterflies is very fragmentary, and it is highly desirable that many more observations should be made upon the subject. If collectors generally would make careful notes, both in the field and upon the freshly killed butterflies at home, we ought soon to be able greatly to extend our knowledge. By holding the butterfly with a pair of forceps, one can often determine whether the fragrance is emitted. It is often helpful also to brush the hairs or tufts where the androconia are attached, using a small, dry camel's hair brush for the purpose. BUTTERFLY MIGRATIONS