The sector of the subgenal suture between the postcoila and the posterior tentorial pit. In mosquito larvae, faint or undeveloped from the postcoila to near the point where the lateralia approach the anterolateral comer of the submentum, then distinct for at least a short distance posteriorly forming the border between the lateralia and the submentum; sometimes traceable to the posterior tentorial pit; often faint or absent posteriorly.
Larvae: hypostomal suture