Technical Note.—The Monarch or Milkweed butterfly is distributed all over the country. It is large, and red-brown in color, and lays its eggs on milk weeds where the greenish yellow and black-banded larvæ (caterpillars) may be found feeding. The covering of scales conceals the outlines of the various external parts, but these scales may be easily removed with dissecting needle and a small brush. In brushing the scales from the head care must be taken not to break off the mouth-parts.

External structure (fig. [41]).—Note the three body-regions, head, thorax and abdomen. Is the body segmented? Note the dark color and firm character of the chitinized cuticle.

Fig. 41.—Body of the monarch butterfly, Anosia plexippus, with scales removed to show the external parts.

Note on the head the large compound eyes. Note the tumid convex clypeus which composes most of the anterior aspect of the head. Are ocelli present? Compare the antennæ with those of the locust and water-beetle. Compare also the mouth-parts and note that they differ radically from those of the locust and beetle. They are not fitted for biting, but for sucking up liquid food (the nectar of flowers). Note the absence of a movable flap-like labrum (a minute narrow stiff piece, bearing at each latera end a small group of fine brown hairs, represents the labrum), the entire absence of mandibles, and the absence of a movable flap-like labium. The labium is a fixed chitinized triangular piece forming part of the floor of the head. Note the long slender proboscis coiled up like a watch-spring. (In fresh specimens this proboscis can be uncoiled and will be found flexible. If dried or alcoholic specimens are being studied, the head of the butterfly should be removed and softened in warm water before the mouth-parts are examined.) On either side of this proboscis is a peculiar pointed process which rises from the under side of the head. These processes are the labial palpi and serve to protect the sucking proboscis. The proboscis itself is composed of the two greatly modified maxillæ. Instead of being short, jaw-like and composed of several pieces as in the locust, in the butterfly each maxilla is a slender, flexible half tube applied against its mate on the opposite side in such a way as to form a perfect tube long enough to reach into the nectaries of flowers when in use and capable of being compactly coiled up at other times. Cut across the proboscis and note the canal in the centre. Try to separate the two maxillæ which compose it.

Make a drawing of the frontal aspect of the head with the eyes and appendages.

Compare the thorax with that of the beetle and that of the locust. The prothorax is a freely movable narrow ring or collar. The mesothorax and metathorax are fused to form a large convex mass, of which fully five-sixths is mesothorax and only one-sixth metathorax. Try to distinguish the boundaries of the two segments. Note the three pairs of legs; the differences in size among them, and the differences between them and the legs of the locust and water-beetle. In one of the legs determine the coxa, trochanter, femur, tibia and tarsal segments. Note the differences between the wings of the butterfly and those of the locust and beetle. Note that the wings are membranous, but are covered with many fine scales (fig. [42]), as is, indeed, the whole body. Rub off some of these scales on a glass slide and examine; note shape, little stem or pedicel of insertion, and longitudinal striations. Examine under microscope a bit of wing from which some of the scales have been rubbed. How are the scales attached to the wing membranes? How are the scales arranged? Note that the wing is colorless where the scales have been removed. All the colors and patterns of the wings of butterflies are produced by the scales.

Make drawings of scales; of parts of denuded wings, and of bit of wing covered with scales.