Fig. 5. Confocal images showing 5 µm optical sections through epiproctodeal gland cells. The images were made at various times in the molting cycle of fourth-instar larvae, and the changes in immunostaining indicate a period of active synthesis of the myoinhibitory peptide (MIP)-like peptide early in the molting cycle. At day 1 (A) and day 2 (B), the gland cells contain very little MIP-immunoreactive (MIP-IR) material. (C) At the onset of spiracular apolysis, distinct MIP-like immunoreactivity appears in the cytoplasm. (D) At the onset and (E) 5 h after head-capsule slippage, the MIP-like immunoreactivity is intense. (F) At 10 h after head-capsule slippage and (G) at the crochet-tanning stage, the MIP-like immunoreactivity of the cytoplasm has diminished. (H) At the airhead stage, the MIP-IR is weak and resembles that of the gland cells at the start of the fourth instar (A). Scale bar, 50 µm.