The subfamily Theclinae is a group of butterflies, often referred to as hairstreaks, with some species instead known as elfins or by other names. The group is part of the family Lycaenidae, the "gossamer-winged butterflies". There are many tropical species as well as a number found in the Americas. Tropical hairstreaks often have iridescent blue coloration above, caused by reflected light from the structure of the wing scales rather than by pigment. Hairstreaks from North America are commonly brown above. Few Theclinae are migratory. Members of this group are described as 'thecline'.