While the Black Swallowtail is not so large as some other members of the group, it is probably the best known to most people. It is found throughout many months of the year in practically all parts of North America south of Canada, and has the habit of flying freely about fields and gardens in search of flowers from which to suck its nectar food, and of plants on which to deposit its eggs. The female butterflies have a remarkable ability in selecting only members of the great family Umbelliferae for this purpose. In consequence the caterpillars are generally to be found feeding upon carrots, parsnips, parsley, and various wild species belonging to this order. (_See plates, pages 48 and 64-65._) The eggs of the Black Swallowtail are laid one in a place upon the leaves of the food plant. Each egg is a small, yellowish, smooth, and ovoid object. It may often be found by watching the butterflies as they fly low in search of umbelliferous plants, and seeing one stop for a minute or so while she lays the egg. About ten days after the egg is laid it hatches into a small black caterpillar marked in a characteristic fashion with a blotch of white in the middle of the body which is suggestive of a saddle. The caterpillar immediately begins to feed upon the green substance of the leaf, continuing thus about a week before the first moult. At this time it does not change much in appearance, still being a spiny creature blackish in color and marked by the curious white saddle. A little later it moults again, retaining its original coloring. At each moult, of course, it gets larger and feeds more freely upon the celery or other plant on which it may happen to be. When the caterpillar becomes about half grown it takes on a very different appearance from that of its early life. The skin is smooth rather than spiny, and the general colors are green, black, and yellow. The ground color of the skin is green, which is marked with black cross-bands along the middle of each body ring. On these bands there are many large dots of orange yellow, the whole coloring giving the insect a very striking appearance, especially when it is placed by itself against a plain background. When they finally become full grown in this larva state, these caterpillars are almost two inches long.