Distinction of Liriomyza sativae larvae
Larval instars of Liriomyza sativae (EPPO A1 list) can be distinguished by the length of their mouth hooks or cephalopharyngeal skeleton.
First instars also have a morphological different mouth hook than later instars.
Sources
Petitt, F.L. (1990) Distinguishing larval instars of the vegetable leafminer Liriomyza sativae (Diptera: Agromyzidae).
Florida Entomologist 73, 280-286