The only error I’m aware of in the Handbook is as follows:
Medon: In Fig. 164 on page 117 of the RES Handbook, the aedeagus labelled “M. piceus” is actually M. pocofer. There is no illustration of the aedeagus of M. piceus. As far as I can tell, all the others are correctly labelled and the corresponding text descriptions of aedeagi are correct.
If anyone knows of other additions or corrections to the Handbook, please leave a comment and I will add them to this page.