Family Lycaenidae (often called gossamer-wing butterflies) includes four groups: blues, coppers, hairstreaks and harvesters. There are only about 100 species in North America. These small butterflies hold their wings over their back when at rest. In most species, the males have greatly reduced forelegs not unlike the brushfoots, but the females have all six legs well-developed. Caterpillars of many hairstreaks and blues possess honeydew glands. Ants milk these caterpillars and in return, protect them from predators. The compact chrysalises are usually found in ground litter.

Gossamer wing coloring comes from two different types of scales: gray, brown and orange scales are pigmented, while blue, green, purple and copper colors derive from the selective light-refracting properties of the scales. The two blues pictured here are very common butterflies here in DuPage County near Chicago; the hairstreaks are fairly rare.