Niuean Blue (Nacaduba niueensis)
This species, which is strictly restricted to the island of Niue, is actually known since 1979, when the first specimen, a female, was collected. The specimen was recognized as something new, but was not described, since only the type specimen was available.
It was, however, only described in 2012. 
The male is more or less completely blackish brown coloured on the upper side, and bears on its wings some very few glossy blue scales, giving the wings a somewhat glimmering appearance.
The caterpillars feed on the leaves of toi (Alphitonia zizyphoides (Solander) A. Gray).
This is the only endemic day-flying lepidopteran species of Niue.
 Jacqueline Y. Miller; Lee D. Miller: The Butterflies of the Tonga Islands and Niue, Cook Islands, with the descriptions of two new subspecies. Bishop Museum Occasional Papers 34: 1-24. 1993
 Brian Patrick; Hamish Patrick: Butterflies of the South Pacific. Otago University Press 2012
 R. B. Lachlan: A new species of Nacaduba Moore (Lepidoptera: Lycaenidae) from Niue, southwestern Pacific Ocean. Australian entomologist, 39(2): 49-54. 2012