Wikipedia
Theclinae
The subfamily Theclinae is a group of butterflies, including the hairstreaks, elfins and allies, in the family Lycaenidae. 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'.