subimago
/ˌsʌbɪˈmeɪɡəʊ/ /ˌsʌbɪˈmɑːɡəʊ/Entomology
noun
The penultimate or subadult stage in the development of a mayfly, prior to the final moult but capable of flight.
Origin
Mid 19th century. From sub- + imago, after German Subimago (H. Burmeister, 1838 or earlier). Compare French subimago.