Butterflies and moths play several important ecological roles:
- Adults pollinate many plants whose flowers attract them with sugar-rich nectar.
- Larvae browse certain parts of plants, including seeds and flowers, influencing the plants’ shape.
- Many predators and parasitoids eat them.
Where do they live?
For an ecosystem to sustain a butterfly or moth species, it must provide the exact requirements for all stages of its life history (egg, larva, pupa and adult). Butterflies and moths live and breed in diverse habitats, including salt marshes, mangroves, sand dunes, lowland forest, wetlands, grasslands and mountain zones. Rock surfaces and bare ground are critical – they are home to the lichen eaten by the larvae, and offer adults places to bask in the sun.
Where species are plentiful
Butterflies and moths abound in most habitats. The particular mix of species depends on the season, time of day, and other plants and animals at the site. Any given locality may have 400 to 750 species. Some fly at night and some fly during the day. Different species emerge as adults at different times of the year. The summer’s warmth brings out the highest numbers, although some moths are only on the wing in late autumn or early winter.
It is a myth that moths are solely nocturnal. Some fly at dusk, while others – particularly adult case moths of the Psychidae family – are active at dawn. Diurnal (day-flying) moths include those in the crambid, larentiine, glyphipterigid, elachistid and choreutid groups.
In New Zealand the richness of species increases from north to south, and is surprisingly high in the mountains of the South Island. This is the opposite to the normal pattern, where the number of species increases towards the equator and tropical regions. New Zealand’s distribution has been shaped by the country’s geological history. In the past 5 million years ice ages and mountain-building have created many open habitats, which are the most favourable environments for butterflies and moths.
Few species are widespread. Forested areas have a relatively uniform moth fauna. In farmland and suburban areas, native and introduced butterflies and moths live together.
Some native species such as the porina moth (genus Wiseana) have adapted so well to lawns and pasture that they have become pests. Long-established exotic arrivals such as several species of clothes moth destroy carpets, stored dry products and clothing. Introduced species continue to arrive, but few become significant pests.
Some recent arrivals have become agents of biological control, selectively attacking weeds such as broom, wild parsnip or hemlock. Some species have been deliberately released to control troublesome plants. The gorse seed-pod moth (Cydia succedana) has been successfully established on gorse.
Recording species numbers
Special light traps can be used to attract and sample nocturnal moths. Their attraction is in fact confusion, but the method is effective – more than 100 species can be recorded in a night. Open-country day-flying species can be sampled by netting and sweeping.