Answer: 1) Exclamation point; 2) Period; 3) Question mark.
Step-by-step explanation: The first sentence consists only of the word "wow," so it is an obvious case of exclamation. "It must be a Hercules beetle" is a statement expressing an inference, so it should end with a period, and in the last sentence, the form "Did you know" clearly belongs to a question, so the question mark must be at the end.