pseudimago
/ˌs(j)uːdɪˈmeɪɡəʊ/ /ˌs(j)uːdɪˈmɑːɡəʊ/(also pseudo-imago) Chiefly Entomology. Now rare
noun
A form or stage that resembles the adult but is not a true adult; especially the subimago of a mayfly.
Origin
Mid 19th century. From pseudo- + imago.