Okay so I might not get any answers to this question, but I’m gonna ask just to see if anyone knows. I was wondering, is there any reliable way to differentiate Menemerus fulvus from Menemerus brachygnathus? (Japan is the place I was identifying them) Or is it best to leave it at genus level? They seem to be very similar and I can’t tell the difference! If it’s impossible, to visually tell the difference, I would like to know so I could go back and fix my IDs I made for M. fulvus. (I didn’t know about the existence of M. brachygnathus)
Not a spider expert but this might be helpful:
From this paper, it appears that females are morphologically identical. They do not state how males differ, but by carefully comparing their descriptions of the males, perhaps you can spot distinguishing characters. Spider taxonomy tend to emphasize genitalia in separating species even if other morphological differences are present.
Thank you both for your help! I suppose that confirms my suspicions. I’ll go back and change the females ID’s to genus level, and carefully review the males to see if I can spot any differences.