pupal / pupil are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
pupal: (adjective) of the insects in the chrysalis (cocoon) or post larval stage.
pupil: (noun) the contractile aperture in the center of the iris of the eye; resembles a large black dot.
pupal: NA
pupil: p·y·UW·p·ah·l
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)