The second axillary in Hymenoptera

The wing base of basal hymenopterans (Insecta) have never been properly described perhaps due to the difficulties of its visualization and understanding the 3D relationships between wing base components. Novel 3D visualization techniques such as microCT and Confocal Laser Scanning Microscopy (CLSM) allow us to provide easily digestible morphological data. The wing base of four basal Hymenoptera and 10 apocritan species have been imaged with CLSM and dissected under a stereomicroscope. The second axillary is composed of two sclerites (on on the dorsal wing membrane and one on the ventral in Macroxyela , Xyela and Athalia whereas it is represented by a single sclerite traversing the wing in other Hymenoptera. Consequences related to this observation as well are drawn and future directions in Hymenoptera wing base studies are provided.