Design

 The poem begins with a simple setup—the first three lines introduce us to the main characters. We have a big white spider on a white flower, poised to eat a white moth. The speaker sees this bizarre little albino meeting as some weird witches' brew, as all three are brought together for some awful reason.
That observation leads the speaker to a series of questions: Why is this flower white, when it is usually blue? What brought the spider to that particular flower? What made the moth decide to flutter by right then?
Frost concludes that if it were "design" that brought these three together, it must be some pretty dark design. In other words, it's not a comforting thought to think that God went out of his way just to make sure this moth got eaten. But that's the crucial "if" of the last line: if design does govern these small things. (What if—gulp—there's no design at all, and everything in life is just totally random occurrences?) The reader is left with just as many questions as Frost. This short poem takes a simple little thought and pushes us all the way to questioning the very nature of creation and life as we know it.