FIGURE 1.

Unsuccessful insect ecdysis accompanying melanization. Morphological changes of integuments on the 4th larval molting stage was performed (A–C). Waxlike matter that can be stained red by eosin was first produced (A and B), and cuticle was then produced in the later molting stage (C). Two hours after 18 h of IV-M (IV-M: 18 h), larval-larval ecdysis will happen. The layer of cuticle becomes thicker during the progress of the feeding stage (D). Compared with DMSO injection (E), injection of 20-E can induce the production of new cuticle (F). The arrows indicate the position of old cuticle (OC) that is eventually shed, and the arrowhead indicates new cuticle (NC) deposited on epidermal cells. Silkworms showed three types of ecdysis: larval-larval (LL; G), larval-pupal (LP; H), and pupal-adult (PA; I). Some silkworms could not shed the old cuticle, after which melanization was observed all over the body. a, normal ecdysis; b, unsuccessful ecdysis. The inset in I (a) represents a normal pupa before eclosion. C, cuticle; E, epidermis. IV-M: X h, X h after the beginning of the fourth molting stage. Scale bar, 20 μm (A–F) or 0.5 cm (G–I).