Which family is known for skimmers?

The family known for skimmers is Libellulidae. Members of this family are often recognized for their distinctive flying behavior, as they are known to skim the surface of water in search of prey, primarily other insects. This behavior is characteristic of many dragonfly species within Libellulidae. The skimmers exhibit a variety of colors and forms, but they typically have wide, flattened bodies and large, often prominent eyes, which aid in their hunting strategies.

In contrast, the other families listed have different characteristics and behaviors. Leuctridae includes stoneflies that are primarily aquatic and are known for their two-winged adults rather than skimming behavior. The Nemouridae family also comprises stoneflies but focuses more on a life cycle involving flowing freshwater habitats without the skimming behavior characteristic of Libellulidae. Pteronarcyidae includes the giant stoneflies, which are also not associated with skimming but rather with larger and often slower-moving aquatic environments.

Thus, Libellulidae stands out for its members' unique skimming behavior, making it the correct answer.