alternative definition added over 14 years ago by Istvan Miko
The paired posterior labral retractors arise on the frons laterally to the anterior retractors and insert on the tormae, the latter sometimes having a dorsal spine at the point of insertion.
Reference: Vilhelmsen, L. 1996. The preoral cavity of lower Hymenoptera (Insecta): comparative morphology and phylogenetic significance. Zoologica Scripta 25:143-170.
Cross reference:
None provided.