Papilio montrouzieri, a blue swallowtail butterfly known locally as "papillon bleu" is, along with the kagu, the "margouillat” (a little gecko) and the striped jersey snake, one of New Caledonia's best-known iconic emblems.
The butterfly typically has a wingspan of about 10 cm and the upperside of the wings are an iridescent electric blue, so it is not easy to miss when fluttering about in search of nectar or a mating partner.
Papilio montrouzieri is widespread both on the Main Island and the Loyalty Islands, and its preferred site for metamorphosis is the Hard Aspen (Acronychia laevis), a tree belonging to the Rutaceae family and commonly found in areas of mining scrub, dry forest and subtropical forest up to 600 metres.
After mating, the female lays her eggs on the leaves of the Hard Aspen tree. Six to seven days later, the hatching larvae will begin to consume their own eggs. The larvae continue to eat leaves greedily for twenty-five days, during which time they grow to their full length and weight. They then produce silk thread to fasten themselves to a branch and turn into a pupa, also known as a chrysalis, identical in shape and colour to the leaves of the Hard Aspen. Thus protected from predators, the larva inside the pupa metamorphoses, over a period of eighteen to twenty days, into an imago, a newly emerged butterfly with moist and crumpled wings.
The wings of the Papilio montrouzieri butterfly, brilliant blue when spread and brown when folded, serve to attract other members of the species for mating and also provide excellent camouflage when the butterfly is at rest.