Fig. 4. Confocal images of whole mounts of epiproctodeal glands immunostained at various times in the molting cycle of fourth-instar larvae, showing a cycle of depletion and subsequent recovery of myoinhibitory peptide (MIP)-like immunoreactivity in the neurohemal system. (A) Moderate staining of the neurohemal system on day 0. (B) Intense immunostaining by the onset of spiracular apolysis. (C) The immunostaining is almost unchanged at approximately 4 h before head-capsule slippage. (D) A pronounced decline in immunostaining is seen by the onset of headcapsule slippage. (E) Most of the immunostaining of the neurohemal system is lost by 5 h after headcapsule slippage but the cell bodies are now well stained (arrow). (F) There is a moderate increase in staining of the neurohemal system by approximately 10 h after head-capsule slippage. (G) The immunostaining continues to increase at the crochet-tanning stage. (H) At the airhead stage, immunostaining of the neurohemal system is comparable with that of the gland of the fourthinstar larva at day 0. (I) An enlargement of a portion of the neurohemal system from C, showing partly vacuous varicosities (arrows). Scale bars, 250 µm (A–H) and 10 µm (I).