Many experts in Ants, Bees, and Wasps have provided me help over the years. These include John S. Ascher, Řistein Berg, Gavin Broad, Matthias Buck, Kelsey J.R.P. Byers, Bob Carlson, James M. Carpenter, Leopoldo Castro, Ben Coulter, Libor Dvořák, Eric Eaton, Nick Fensler, Paul Hanson, Ross Hill, Kamil Holy, Victor Kolyada, William Mackay, Paul Marsh, Michael Ohl, James Pitts, Wojciech Pulawski, Claus Rasmussen, Christian Schmid-Egger, Michael Sharkey, Scott R. Shaw, Dave Smith, Gordon C. Snelling, Eckart Stolle, Camille Thirion, James C. Trager, Gergely Várkonyi, Richard Vernier, Cecilia Waichert, George Waldren, Christopher M. Wilson, Harmut Wisch, Ken Wolgemuth, Matt Yoder, and Bob Zuparko.
In developing the species pages I have mined a number of scholarly articles old and new, and these are listed in the Works Consulted page for Hymenoptera.
Above all, I want to thank my many friends and colleagues at the Bugguide.net website, who help with IDs, provide stimulating conversation about hexapods, and mutual support. Many of these are listed in the overall Acknowledgments page for the American Insects site.