Breeding bag moths in captivity
LAST week, two different kinds of bag moths — the large common bag moth and the rarer faggot moth — were brought to the museum. These belong to the family Psychidae, in which the caterpillars construct bags of silk, leaves, bark, twigs, moss, or lichen. Adult females are usually wingless and spend their entire lives within the bags, even laying eggs and dying there, whereas the males are fully winged moths. Fortyseven of the 51 described species in New Zealand are endemic.
Faggot moths (Orophora
unicolor) occur at higher altitudes in Otago (e.g., Rock and Pillar Range) on matagouri, tauhinu, and beneath stones. The common bag moth (Liothula omnivora) is found on many different shrubs in Dunedin gardens, where the larvae eat leaves. They are easy to keep on a manuka twig in water, but note that they wander. A high proportion of common bag moths are attacked by parasitic wasps and flies. The small Australian lichen bag moth Cebysa leucotelus appeared on North Island houses in the 1980s.
Less well known are New Zealand’s miniature bag moths. Their tiny cases are often less than 8mm long — the case of one species does not exceed 4mm when fully grown. There are at least 30 species of these, and several remain undescribed. Curved case moths (genus
Grypotheca) occur in native leaf litter throughout New Zealand, and are abundant on Leith Saddle and Mt Cargill.
Other kinds of small bag moths often abound on tree trunks and posts. These caterpillars, in their tiny bags, hide in crevices during dry weather, but spread out after rain to feed on the green singlecelled algae that flourish on wet posts, boards and tree trunks.
Yet other tiny bag moths occur on white crustose lichens growing on bark and rocks. Four species of the latter occur on lichencovered rocks on the coastal cliffs between
Lawyers Head and Cape Saunders (genera Scoriodyta, Mallobathra,
Reductoderces, and Rhathamictis occur on Otago Peninsula).
To rear miniature licheneating bag moths, break off fragments of lichencovered rock or bark and place them in a lunchbox or similar container. Place the bagmoth larvae on the lichen and remember to put one or two drops of water on the lichen every four days or so. The bag moths will die if this is not done. Adult moths of most species appear in spring and summer, but those of one tiny bag moth present on a lichen on Otago Peninsula emerge in July. Several other kinds of insects also feed exclusively on lichens, and the secret to breeding them in captivity is to keep the lichen moist.