Ante-alar sinus: Odonata; a grooved area extending transversely immediately in front of the base of each front wing.
"Explanation of Terms Used in Entomology" by John. B. Smith
The transverse (lateral), superior sagittal (longitudinal), and cavernous sinuses are those most frequently damaged.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition." by Alexander Miles
As the ducts of Cuvier come from each side the sinus spreads out to meet them and becomes transversely elongated.
"Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2" by Various