Q: What conditions have to exist in a world to explain giant insects? — EXCELLENT
Q: What would the world be like if it were ruled by giant insects? — TOO BROAD
On the one hand, you could argue that the present question follows the "what conditions have to exist..." form and is thus on-topic. On the other hand, it feels very open-ended; the number of (credible) answers that explain giant-insect overlords should be much smaller than the number of answers brainstorming about government collapse.
Is the government-collapse question ok? Too broad? And, more generally, where is the line between the focused, answerable, "what conditions cause..." questions that we want and the "help me brainstorm my plot" questions that are better-suited for a writing group?