Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Lycaenidae
Genus: Zizina
Species: Z. otis
Subspecies: Z. o. labradus
Binomial name: Zizina otis ssp. labradus,
Synonym: Zizina labradus labradus
Common name: Common Blue, Pepe Ao Uri
Zizina otis ssp. labradus is probably our most common butterfly (originally windblown from Australia) It is a small butterfly (up to 23mm wingspan) with a weak, fluttering flight and so it usually flies close to ground level close to a food source. In some areas, it is considered a pest species as one trail recorded over 300 larvae per square metre on drought-prone pasture.
They lay single eggs which are laid and can hatch in a matter of days. The eggs are laid on leaves, stems, flower buds and young pods of food plants, chiefly legumes of the Fabaceae family such as beans, clover and various native species. Newly hatched larvae eat small holes from young leaves or flower buds and later feed mainly on flowers.
For more details visit: http://nzbutterfly.info/downloads/nzButterfly.info-factsheet-common-blue.pdf
They certainly like the flowers of Sedum. The next two photos are of the same butterfly.