Acheron's a juvenile, about 4" diagonally, not sure if they're too young to sex yet but I figured I'd post the underside as they're chilling out on the side of the enclosure right now and it's a great time to get some shots. I compiled some of the clearer shots into this pic, including a palp pic.
@kaolincash It's different from species to species. In all cases, though, the field of epiandrous fusillae has shorter and more dense setae than the rest. You can see it extremely well in the lower right pic: a more orange-ey, oval shaped field directly above the furrow.
In A. seemanni it's relatively large, in other species it can be smaller, in can be oval, a half circle, a dot, or a triangle, darker or lighter or whatever. Find a spot above the epigastric furrow that is different from the rest of the setae.
@boina Could you do me a favour and annotate the picture I posted? I've been trying to search online but I can't find anything I can correctly parse.
Don't worry if that's too much of a hassle for you, or if you don't have an image editor, so do you know anyone else I can ask about this stuff who can take me aside and give me all the right details in a way I can understand?
At any rate, thanks everyone for your responses here - I've now ordered a female seemanni so hopefully I'll be able to sell some slings once Acheron