It is a quite commonly held misconception that the Small Redeye/Small Red-eyed Damselfly (Erythromma viridulum) sports a black dot on the side of the abdomen separated from the black spur whereas the Large Redeye/Red-eyed Damselfly (E. najas) does not show a separated black dot.
It is true that this is frequently the case but it is nowhere near infallible as these two counter-examples of each show.
