ABSTRACT.Pupation site preference and body orientation of potato tuber moth larvae,Phthorimaea operculellaZeller (Geleehiidae), were examined in the laboratory. The larvae preferred a dry, enclosed, dark place as their pupation site. Dryness was the strongest of the three categories of stimulus; the second was stimuli evoking thigmotaxis; the third was darkness. Having selected a pupation site, a larva oriented its head to the open side of the site. If two or more openings were present, final orientation was influenced by light and gravity. These preferences and orientation habits enhance pupal protection, and the ultimate successful exit of the adult pupation crevices.