FACT: Pitou is a guy.

Every ant, except the queen, is a male. Every ant has a penis and is capable of procreating with females from other species.

Pitou looks like a girl because of phagogenesis. The queen ate females and laid his egg. Pitou calls himself a male.

And also remember that real life male house cats have "feminine curves" compared to our human standards. So a cat-like male would look girly to us.