Her previous trips were to Australia, Colorado, and Hawaii, so she probably wasn't expecting quite so many insects. (It's a bit of a shock, even in modern times, once you get even slightly out of the city)
And yes, "creature" was a way of saying "person" back in the 1800s-ish that has since fallen out of use. Jane Austen uses it pretty often in her works, notably in Pride and Prejudice when Elizabeth gets engaged to Mr. Darcy and says of herself, "I am the happiest creature in the world."