CONTRIBUTIONS TO THE STUDY OF DEVELOPMENT OF THE WING-PATTERN IN LEPIDOPTERA

¹ From the Department of Zoölogy, University of California, Berkeley, California

1. Goldschmidt's observations and ideas on the problem of different velocities of development for different parts of a pattern are described. The experiments of Kühn and his school and their negative views in regard to the idea of different velocities of developmental processes are summarized.

2. New observations confirm the existence of the "relief-stage" in the pupal wing of Platysamia cecropia and Papilio ajax, as well as in Ephestia k., where it has not been previously observed.

3. It was observed that the relief-stage proceeds over the pupal wing from the proximal base to the distal margin in a wave-like fashion as is the case with the mitosis-pattern. The relief stage and the mitosispattern appear on the hind wing earlier than on the front wing.

4. No difference in growth of the scales was observed in sections through the wing during the relief-stage.

5. With the help of a chitin-reaction it could be shown that during the relief-stage the subsequent light parts of the wing were more chitinized than the subsequent dark parts.

6. A test with polarized light during the relief-stage gave no clear results.

7. With the help of artificial pigmentation (tyrosine-reaction) a complete pattern can be produced on the still unpigmented wing long before the relief-stage could be observed.

8. This tyrosine-reaction shows that a certain condition of the chitin is necessary to deposit pigment in the scales. Subsequent light parts of the wing are more chitinized at the time of pigmentation than subsequent dark parts and therefore cannot deposit any pigment. This experiment proves that the different velocities of development of the different parts of the pattern lead to the pattern of pigmentation.

9. By dissolving scales from subsequent dark and light districts in H₂SO₄ during the relief-stage and dark and light scales on the mature wing, it could be actually shown that the scales are differently chitinized at the time of pigmentation and equally chitinized on the mature wing.

10. The similarity of processes during the mitosis-period and the relief stage and their general appearance in different species of Lepidoptera allow us to correlate them. Both stages express the different velocities of developmental processes for different parts of the wing, which finally produce the pattern of pigmentation.