When sexing any crab you can clearly see that on females the underneath "flap" is much wider and shorter and on males the "flap" is much narrower and longer. Naturally you dont have to go to such traumatic ways of sexing them as you will be able to see clearly just from looking at your crab whether it is male or female.
This page which is featured is from the book: Aqualog special, shrimps, crayfish and crabs in the freshwater aquaruim by Uwe Werner
