|Image by Waugsberg in Wikipedia|
He also determined that the three least painful locations to be the skull, middle toe tip, and upper arm (all scoring a 2.3 out of possible 10). The three most painful locations were the nostril, upper lip, and penis shaft (9.0, 8.7, and 7.3, respectively). Pain was rated on a 1–10 scale relative to an internal standard, the forearm.
The complete list of body locations in rank order can be found here.
Of course, this study was conducted on only one subject (the author) and as such, conclusions may not be entirely valid if done on a larger group of people.
However, I'm not sure how many people would volunteer for this kind of study and it is doubtful IRB would approve of any proposed study that would deliberately sting volunteers to various parts of the body including the genitals.
This may be a "one-of-a-kind" study.
Honey bee sting pain index by body location. PeerJ 2:e338 http://dx.doi.org/10.7717/peerj.338