There's a snake on my foot and I'm not screaming.
This is situational irony because the colonel says that women panic whenever they see something they don't like, but the women has a cobra on her foot and she is staying calm.
This is dramatic irony because the reader knows that there is a cobra under the table, but the guest do not. Only the maid, the colonel, and Mrs. Wynnes knows that there is a cobra under the table.
The theme is that your gender doesn't matter how courageous you are. In the story, it is shown by how a little girl and a colonel arguing over whether women freak out over everything. The colonel was wrong about what he said because when a cobra came in the room, nobody freaked out because he told everyone to play a game, but Mrs. Wynnes was the one who really stayed calm because the cobra was on her foot.