The metamorphosis is complete, the contrast between the caterpillar or larva of the moth and the butterfly and the adult form being very great. The caterpillar has the three pairs of jointed legs typical of insects; these are found near the head (Fig. [141]). It has also from three to five pairs of fleshy unjointed prolegs, one pair of which is always on the last segment. How many pairs of prolegs has the silkworm caterpillar? (Fig. [143].) The measuring worm, or looper? (Fig. [136].) The pupa has a thin shell. Can you see external signs of the antennæ, wings, and legs in this stage? (Fig. [143].) The pupa is concealed by protective coloration and is sometimes inclosed in a silken cocoon which was spun by the caterpillar before the last moult. Hairy caterpillars are uncomfortable for birds to eat. The naked and brightly marked ones (examples of warning coloration) often contain an acrid and distasteful fluid. The injuries from lepidoptera are done in the caterpillar stage. The codling moth (Fig. [141]) destroys apples to the estimated value of $6,000,000 annually. The clothes moth (Fig. [171]) is a household pest. The tent caterpillar denudes trees of their leaves. The only useful caterpillar is the silkworm (Fig. [143]). In Italy and Japan many of the country dwellings have silk rooms where thousands of these caterpillars are fed and tended by women and children. Why is the cabbage butterfly so called? Why can it not eat cabbage? Why does sealing clothes in a paper bag prevent the ravages of the clothes moth?
Flight of Lepidoptera.—Which appears to use more exertion to keep afloat, a bird or a butterfly? Explain why. Of all flying insects which would more probably be found highest up mountains? How does the butterfly suddenly change direction of flight? Does it usually fly in a straight or a zigzag course? Advantage of this? Bright colours are protective, as lepidoptera are in greatest danger when at rest on flowers. Are the brightest colours on upper or under side of wings of butterfly? Why? (Think of the colours in a flower.) Why is it better for moths to hold their wings flat out when at rest? Where are moths during the day? How can you test whether the colour of the wings is given by the scales?
State how moths and butterflies differ in respect to: body, wings, feelers, habits.
Insects and Flowers.—Perhaps we are indebted to insects for the bright colours and sweet honey of flowers. Flowers need insects to carry their pollen to other flowers, as cross-fertilization produces the best seeds. The insects need the nectar of the flowers for food, and the bright colours and sweet odours are the advertisements of the flowers to attract insects. Flowers of brightest hues are the ones that receive the visits of insects. Moths, butterflies, and bees carry most pollen (see Beginners’ Botany, Chap. VI).
Comparative Study.—Make a table like this, occupying entire page of notebook, leaving no margins, and fill in accurately:—
| Grasshopper | Butterfly | Fly pp. [92], [93] | Dragon Fly p. [93] | Beetle pp. [90], [91] | Bee pp. [88], [89] | |
| Number and kind of wings | ||||||
| Description of legs | ||||||
| Antennæ (length, shape, joints) | ||||||
| Biting or sucking mouth parts | ||||||
| Complete or incomplete metamorphosis. |
Fig. 141.—Codling Moth, from egg to adult. (See Farmers’ Bulletin, p. 95.)
Fig. 142.—Cabbage Butterfly, male and female, larva and pupa.