But should you examine these buds with care, you will find a number of small caterpillars, the larva of the beautiful Azure Butterfly, called _Lycæna pseudargiolus_, feeding thereon. During its younger stages it is white, and so near the color of these buds that it is well protected, and very difficult to find. Later on, it may be white or greenish, and often diversified with a few black or brown patches, irregularly diffused over the surface. When mature the larva is one-half of an inch in length, and, like all Lycænid larvæ, is onisciform, or shaped like the little pill-bug, so common under stones and logs. The head is very small, and is placed on the end of a long, green neck, which at the junction is of the thickness of the head, but gradually enlarges, and seems to be fixed at the hinder part of the second segment, the latter being hollowed out so as to form for it a sheath. In the final larval stages this segment is elevated, transversely compressed, and inclines forward, thereby shielding the head as the larva moves about. When quiescent the neck and head are wholly retracted, and as the former, when fully extended, is very much longer than the depth of the second segment, it must possess considerable elasticity. The larva feeds on the heart of the bud, and to reach this cuts away the surface on one side till an opening is made sufficiently large to admit its head; and as it feeds the second segment is firmly pressed against the bud so as to permit the utmost elongation of the neck. Thus it is enabled to eat out the contents of the bud, and only desists when there remains but the empty shell. When so engaged the anterior segments are curved up and the others rest upon the stalk of the plant, but very small larvæ repose wholly in the bud. Not a single instance has been observed where an open flower has been attacked, but the destruction of buds is very extensive. But now comes the most remarkable part of the larval history of Pseudargiolus. The whole upper part of the larva is covered with small, glassy, star-shaped processes, scarcely raised above the surrounding surface, from the centre of which spring short, filamentous bodies, bristling with feathery-looking tentacles, which the caterpillar has the power of protruding at will. It throws them out like the tentacles of Papilio or the horns of snails. More singular still is an opening upon the eleventh segment, placed transversely and surrounded by a raised cushion, about which the granulations that cover the body of the caterpillar are particularly dense. From the middle of this opening, which is shaped like a button-hole, issues, at the caterpillar’s will, a sort of transparent, hemispherical vesicle, from which is emitted a good-sized drop of fluid, which the animal is capable of reproducing when absorbed. [Illustration: PSEUDARGIOLUS BUTTERFLY. Larva Feeding on Bud of Black Snakeroot, and Guarded by Ants.]