This image is an example of situational irony. The colonel was saying how women will always panic in times of a crisis and how men will maintain their control and calmness. When the snake enters the room the woman did not panic at all. The situation of the story was contradicting what the colonel believes.
This image is an example of dramatic imagery. The reader knows that there is a cobra in the room, but the young girl and the colonel don't know.
The theme of this story is your gender has no impact on how courageous you are. This theme is showed when Mrs. Wynnes was calm when the snake slithered over her foot.