Major Institutions and Authorities (Europe)
Atlas Hymenoptera The website of University Mons (Belgium).
Chrysis.net. The best site for those with an interest in Chrysididae 
Faszination Wildbienen. The website of Paul Westrich (In German)
HymIS. Hymenoptera Information System (in German)
www.hymenovaria.nl. The Hymenoptera section of the Dutch Entomologists Union (NEV)
Wildbienen Kataster. The website of The Stuttgart Entomological Union