hypostomial

[…] typically there is a transverse row of nine conical teeth in which the outside pair and the middle tooth are prominent, but mature larvae of Simulium neavei group have 13 hypostomial teeth of about equal size, and in Gymnopais the teeth are flat and chisel-like in association with loss of cephalic fans and the needs to scrape food from the substrate instead of filtering it from the current.

2012, R.P. Lane, Medical Insects and Arachnids, page 245