Why does the author begin the essay with a comparison between night moths and day moths?

The speaker opens the essay with a comparison between moths that appear at night and those that appear during the day, noting that the latter "do not excite that pleasant sense of dark autumn nights and ivy-blossoms which the commonest yellow-underwing asleep in the shadow of the curtain never fails to rouse in us" (1). This opening sets up the subject of the essay, the day moth, along with the speaker's surprise over how it seemed "content with life" (1). This instance is the first of many in which the speaker will be surprised by the moth she observes. Furthermore, this particular comparison between the two types of moths suggests that these small insects can arouse emotion in people. The speaker will prove this idea throughout the essay as she questions how to...