Leather-leaf spore-eater - Calicotis crucifera
By N A Martin (2010, revised 2016)
Biostatus and Distribution
This endemic moth is found throughout New Zealand where the caterpillar feeds on spores of its endemic host plant, leather-leaf fern, Pyrrosia eleagnifolia. The moth is present in cities and native ecosystems.
Conservation status: Widespread, not threatened.
Life Stages and Annual Cycle
Several sizes of caterpillars and pupae are present in spring. Moths have been found from October to May, indicating that the moth may breed all year round.
Adult moths have slim grey wings with darker specks and long hairy posterior margins. They also have a distinctive hairy hind pair of legs that are held out from the body usually at right angles forming a cross-shape, hence the name ‘crucifera’.
Eggs are assumed to be laid on the fertile fronds of its host plant, presumably near the sporangia. Tiny caterpillars hatch from the eggs and may be found in silk-lined burrows around the fringe of sporangia. The caterpillars feed on the fern spores. As the caterpillar grows, it moults (changes its skin). The caterpillar reaches 6 mm long. Older caterpillars make long silk-lined tunnels through the stellate hairs covering the underside of the fern frond. These silk galleries link the sporangia and are covered with the stellate hairs and remains of sporangia. The caterpillar may move to other fertile fronds.
When the caterpillar is fully grown, it makes a silk-lined chamber coated with debris on the underside of the frond and moults into a pupa. After a few weeks, a moth emerges from the pupa. It finds a place to rest while the wings expand and the wings and the cuticle of the body harden.
There are many kinds of thin grey moths, but the leather-leaf spore-eater can be recognised by its hairy hind legs that are held out at right angles to its body.
The leather-leaf spore-eater is the only caterpillar that feeds on spores of leather-leaf ferns, so its presence can be recognised by the results of its feeding and the silk-lined galleries on the undersides of fertile fronds.
No natural enemies of this moth are currently known. Birds and spiders are likely to prey on the adult moths. There are also likely to be parasitoids of the caterpillars.
The leather-leaf spore-eater, Calicotis crucifera, has only one host plant, the leather-leaf fern, Pyrrosia eleagnifolia (Bory) Hovenkamp (Polypodiaceae).
The caterpillars feed on the fern spores. They make silk-lined tunnels covered by stellate hairs of the fern and spores. Their feeding reduces the number of viable spores released by the fern, although this does not appear to limit the spread of the fern and its ability to colonize new sites.
Crowe A 2004. Life-size guide to New Zealand ferns. Albany, Auckland, New Zealand, Penguin Group (NZ). 32 p.
Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.
Robert Hoare for information about the moth.
The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.
19 May 2016. NA Martin. Recognition: photo of moth added. Other images of caterpillar damage added.