How can you tell? The way I try to tell with P. imperator is by looking at the shape of the body. To me, gravid emps have a shape that looks like a squash, with the carapace being the thinning end(neck)of the squash shape. Premolt and mature fat emps seem to be more shaped like a football, of course immatures have a light telson. I took pics but didn't upload, they're really bad pics. I have an emp that I think will have babies any day now, squash shaped. A lot of people are bored with emps, I think mostly because they are so available, but scorplings from this female are important to me because they will be from both 6 inch male and female imperator parents. I plan to take them to maturity to check out the size, easy enough, low maintenance. Anybody notice this with their other species? But what if you have a gravid AND fat emp lol?