Each summer, public health officials in California make the rounds to "sentinel chickens" in semi-secret locations all over the state. These ordinary chickens just puttering around in their coops have an important job—without them, we'd be more clueless about where West Nile virus is.
Spiders have been a plague on the earth ever since they marched their eight feet out of hell. In some areas, spiders have been known to cocoon entire trees. And it turns out there's a benefit to their efforts.
Put this one in the "We'd feel bad about it if they were mammals" files. With dengue fever infections on the rise and two fifths of the world's population at risk, scientists devise a scent trap that kills pregnant mosquitos.