Albinism and Melanism.—Albinos, white or light-colored forms, are quite common among butterflies, principally among the females. On the other hand, melanism, or a tendency to the production of dark or even black forms, reveals itself. Melanism is rather more common in the case of the male sex than in the female sex. The collector and student will always endeavor, if possible, to preserve these curious aberrations, as they are called. We do not yet entirely understand what are the causes which are at work to produce these changes in the color, and all such aberrant specimens have interest for the scientific man.
Monstrosities.—Curious malformations, producing monstrosities, sometimes occur among insects, as in other animals, and such malformed specimens should likewise be preserved when found. One form of malformation which is not altogether uncommon consists in an apparent confusion of sexes in specimens, the wings of a male insect being attached to the body of a female, or half of an insect being male and half female.
Mimicry.—One of the most singular and interesting facts in the animal kingdom is what has been styled mimicry. Certain colors and forms are possessed by animals which adapt them to their surroundings in such wise that they are in a greater or less degree secured from observation and attack. Or they possess forms and colors which cause them to approximate in appearance other creatures, which for some reason are feared or disliked by animals which might prey upon them, and in consequence of this resemblance enjoy partial or entire immunity. Some butterflies, for instance, resemble dried leaves, and as they are seated upon the twigs of trees they wholly elude the eye. This illustrates the first form of mimicry. Other butterflies so closely approximate in form and color species which birds and other insects will not attack, because of the disagreeable juices which their bodies contain, that they are shunned by their natural enemies, in spite of the fact that they belong to groups of insects which are ordinarily greedily devoured by birds and other animals. A good illustration of this fact is found in the case of the Disippus Butterfly, which belongs to a group which is not specially protected, but is often the prey of insect-eating creatures. This butterfly has assumed almost the exact color and markings of the milkweed butterfly, Anosia plexippus, which is distasteful to birds, and hence enjoys peculiar freedom from the attacks of enemies. Because this adaptation of one form to another evidently serves the purpose of defense this phenomenon has been called "protective mimicry." The reader who is curious to know more about the subject will do well to consult the writings of Mr. Alfred Russel Wallace and Mr. Darwin, who have written at length upon mimicry among butterflies. There is here a field of most interesting inquiry for the student.
The Distribution of Butterflies.—Butterflies are found everywhere that plant life suited to the nourishment of the caterpillars is found. There are some species which are arctic and are found in the brief summer of the cold North and upon the lofty summits of high mountains which have an arctic climate. Most of them are, however, children of the sun, and chiefly abound in the temperate and tropical regions of the earth. While the number of species which are found in the tropics vastly exceeds the number of species found in the temperate zone, it is apparently true that the number of specimens of certain species is far more numerous in temperate regions than in the tropics. Very rarely in tropical countries are great assemblages of butterflies to be seen, such as may be found in the summer months in the United States, swarming around damp places, or hovering over the fields of blooming clover or weeds. In the whole vast region extending from the Rio Grande of Texas to the arctic circle it is doubtful whether more than seven hundred species of butterflies are found. On the continent of Europe there are only about four hundred and fifty species. The number of species of butterflies and the number of species of birds in the United States are very nearly the same.
CHAPTER II
THE CAPTURE, PREPARATION, AND PRESERVATION OF SPECIMENS
"What hand would crush the silken-wingèd fly, The youngest of inconstant April's minions, Because it cannot climb the purest sky, Where the swan sings, amid the sun's dominions? Not thine."
Shelley.