Mid 19th century; earliest use found in Proceedings of the Academy of Natural Sciences of Philadelphia. From sub- + scientific Latin imagin-, imagoimago + -al, after subimago; compare slightly later imaginal.
Definition of subimaginal in US English:
subimaginal
adjective
Entomology
Belonging to or characteristic of the subimago.
Origin
Mid 19th century; earliest use found in Proceedings of the Academy of Natural Sciences of Philadelphia. From sub- + scientific Latin imagin-, imago imago + -al, after subimago; compare slightly later imaginal.