I remember LBreeze asking me about the gender of my hermit crabs. I got curious and so a few weeks ago after the crabs' weekly bath, I finally turned them over and checked.
A female hermit crab has gonopores or 2 holes on their 3rd set of legs as shown below. The males have no holes underneath. It's hard to get the crabs to show you their underbelly, but I've found that they are more willing to do so after taking a bath.
I was surprised to dicover the genders of my crabs, after all I have named most of them already. Anyhoo, their names stay regardless of their sex.
Gigantor - male
Hercules - male
Georgey - male
Mortimer - male
Cornelia - male
1 unnamed crab - male
Maximus - female
Purple Pincher - female
1 unnamed crab - female
The males outnumber the females in my tank!
I can't say if the males are more aggressive than the females or vise versa. Their personalities vary, sometimes Max bullies all the smaller crabs, and other times Gigantor is the timid one.