The fly narrating this informative picture book is full of enthusiasm, not to mention knowledge, eager to convince a class studying butterflies that flies are just as worthy a subject. “Here’s how the story goes: My 500 brothers and sisters and I started out as eggs. Our mom tucked us into a warm, smelly bed of dog doo.” The fly’s impromptu lecture (it came in through the window during a science class) is followed by a Q-and-A session, with the fly dispelling misinformation about its species. Bridget Heos’s funny, factual narrative (well, except for the talking fly) is perfectly matched by Jennifer Plecas’s clean-lined, cartoonlike illustrations. (Ages 6–9)