Color pattern formation on the wing of the butterfly Pieris rapae. 1. Cautery induced alteration of scale color and delay of arrangement formation.

Experimental approaches to color pattern formation of lepidopteran insects have been made exclusively by analyzing pattern alterations in adult wings induced by operations. We microcauterized the presumptive black region of the dorsal forewing of the butterfly Pieris rapae and analyzed not only the resultant color pattern in the adult wing but also the cell behavior in the pupal wing epidermis around the injury. Cautery induced color alterations were as follows: (i) cautery up to 49.5 h after pupation resulted in white regions appearing within the black region while later cauteries induced larger white regions; (ii) cautery between 50 and 59.5 h resulted in the white regions induced by the cauteries being dramatically decreased; (iii) cautery after 60 h resulted in white regions that had almost disappeared. The examination of the cell behavior in the pupal wing epidermis after cauteries showed that the row formation of scale precursor cells was delayed. This delayed area varied with the time of cautery, in the same manner as that in the induced white area in the adult wing ((i)-(iii) above). The relationship between scale color alteration and the developmental delay of the scale row formation is discussed.