Several species, chiefly those in the genera Melanagromyza and Napomyza, are internal stem borers, feeding within the pith of the stem, whilst a few are also known to feed within the roots, such as Melanagromyza fabae Spencer, 1973. The images below show a puparium of Melanagromyza lappae (Loew, 1850) inside the stem of greater burdock (Arctium lappa) and a puparium of Napomyza hirticornis (Hendel, 1932) inside a Centaurea stem, with the larva’s feeding channel in the pith clear to see.

Split stem of greater burdock (Arctium lappa) showing Melanagromyza lappae (Loew, 1850) puparium and feeding channels © Barry P. Warrington

Puparium of Napomyza hirticornis (Hendel, 1932) within knapweed stem © Barry P. Warrington