SEXING TRUE CRABS
Adult true crabs can be easily sexed by looking at their undersides, specifically their abdomen a.k.a. the "apron". Typically, mature females have a very broad, convex abdomen, whilst in males this is narrow (see images below). However, note that an immature female has a triangular-shaped abdomen (still differing from the male), whereas a mature female's is usually clearly convex.