alternative definition added over 7 years ago by Istvan Miko
A longitudinal ridge or pair of ridges on the frons between (and sometimes partly covering) the toruli.
Reference: Goulet, H., and J. T. Huber. 1993. Hymenoptera of the World: An Identification Guide to Families. Research Branch, Agriculture Canada Publication 1894/E., Ottawa, ON 668 pp.
Cross reference: None provided.