Butterflies and moths are members of the insect order Lepidoptera (from the Greek meaning ‘scaly wings’). Globally, Lepidoptera is the group with the most insect species associated with flowering plants. There are more than 350,000 known species, 20,000 of which are butterflies.
Like other large insect orders, the Lepidoptera group contains members with a variety of forms, behaviours and ecologies. They are grouped into about 39 superfamilies worldwide, of which 16 are represented in New Zealand. Of 120 families, 35 occur naturally in New Zealand. Two are butterflies and the rest are moths.
Moth or butterfly?
‘Moth’ and ‘butterfly’ are common names given to insects of the order Lepidoptera. There is no strong scientific basis for these terms. There is an evolutionary continuum from the most ancient moth group to the most sophisticated butterfly group. Some moths are more closely related to butterflies than to other moths.
There are some general differences between moths and butterflies. Moths usually hold their wings flat while resting, have feathery antennae, and are active at night. Butterflies tend to be more brightly coloured, have clubbed antennae, hold their wings erect while at rest, and are active by day. But there are exceptions to these generalisations. Many New Zealand moths fly during the day or at dusk. The black mountain ringlet butterfly holds its wings flat while at rest. Some New Zealand butterflies are drab, and most people would call them moths. One sure way to distinguish the two in New Zealand (this does not apply globally) is that all native butterflies have clubbed antennae.
Essentially, however, there is no consistent difference between butterflies and moths. Any superficial differences become exaggerated in a temperate country like New Zealand, where many of the larger, highly developed moth groups (which are more like butterflies) found in warmer countries are missing.
Endemic species are those that are unique to a particular area. New Zealand’s Lepidoptera order displays the world’s highest rate of endemism. The majority (92%) of species are found nowhere else. By comparison, Britain shares its Lepidoptera fauna with mainland Europe, and none of its species are endemic.
New Zealand’s butterflies and moths are distinctive for several reasons. They have:
- a high rate of endemic species and genera
- a number of ancient families, including the superfamily Mnesarchaeoidea, which is found nowhere else
- in comparison with other places worldwide, some families that are well represented, and others that are poorly represented or missing completely
- a high proportion of species whose larvae feed on detritus and leaf litter
- a large number of brightly coloured day-flying moth species, especially in alpine zones and areas of open vegetation.
New Zealand species are significantly different from Australian species.
Lepidoptera is one of the three most species-rich insect orders in New Zealand, and moths and butterflies are relatively well studied. The total number of native species is not accurately known as many new species continue to be discovered, although it is likely to exceed 2,000. Traditionally it has been accepted that New Zealand has about 20 butterfly species. Only 12 have been formally described. Recent research suggests that there may be a further 25 types of copper butterfly, along with new black mountain ringlets and other native species. If this new research proves correct, the total number of butterfly species may be about 70. Of these, 10 are tropical species that are periodically blown over from Queensland, Australia, of which two have become established. An additional four species have been introduced by humans, of which the familiar cabbage white (Pieris rapae) is the most conspicuous.
This rich biodiversity includes the large pūriri moth (Aenetus virescens), which lives in North Island forests and attains a wingspan up to 15 centimetres, and the pinhead-sized, leaf-mining moths of the family Nepticulidae, with wingspans of just 2 millimetres.
An additional 68 moths have been deliberately or accidentally introduced since European settlement, and have established wild populations.
Early entomologists including George Hudson and Alfred Philpott have left a legacy of illustrated books and articles on the country’s moths and butterflies.