INTERESTING INSECTS

By N A Martin (2015, revised 2018)

Karamu leafminer

Parectopa zorionella Hudson, 1918

This moth belongs to the subfamily Phyllocnistinae, and is not related to true Acrocercops, which belong to another subfamily. Hence the apostrophes around the genus name.

This endemic moth forms leaf mines in its endemic host plants, large-leaved species of Coprosma, and is found in the North Island and South Island. It appears to be restricted to native ecosystems, even occurring in small reserves of native ecosystems in urban areas.

Conservation status: Widespread, not threatened.

Leaf mines with caterpillars can be found every month of the year. There are 3 or 4 generations a year in warmer regions of New Zealand (e.g. Auckland),and fewer generations in colder areas.

Adult moths are long and narrow at rest and about 5-6 mm long. The moth holds its wings roof-like over its body. The dark wings have bluish reflections and small white marks forming three narrow bands. It is presumed that the adult male and female moth are attracted to each other and mate. The female moth then lays eggs.

Caterpillars and leaf mines

Eggs are laid singly on the underside of leaves and have a shiny shell. The caterpillar hatches from an egg and tunnels directly into the leaf forming a narrow mine just under the epidermis (skin) of the underside of the leaf. After some distance the caterpillar tunnels through the leaf and forms a mine under the epidermis on the upper side of the leaf. The mine is initially narrow and serpentine, but as the caterpillar grows the mine gradually widens and may form a large blotch. As it gets bigger, the caterpillar moults (changes skin). When fully grown the caterpillar is about 6-7 mm long. The caterpillar is white with a flat brown head that has protruding jaws in front. It uses the jaws to bite off pieces of internal leaf tissue at the edges of the leaf mine. The caterpillar feeds mainly on the sap (juices) from the plant cells, ingesting very little solid tissues. The mine contains the black frass (insect faeces). The legless caterpillar has prominent segments of the body that help it move through its mine.

Cocoon and pupa

When the caterpillar is fully grown, it makes a thin, silk-lined chamber in the leaf mine. The location of the cocoon often shows on the outside as a raised area on the upper surface of the leaf. The caterpillar moults into a pupa, which is white at first and then turns brown. Shortly before moth emergence, the colour of the wings and legs can be seen. At the apex of the head is a sharp spike. This is used by the moth to break through the cocoon and skin of the leaf. When the moth is ready to emerge, the pupa wriggles forwards, makes a hole in the leaf surface, and forces most of itself out of the leaf. At the rear end of the pupa are two hooks (see drawing). The hooks grip the silk cocoon and hold the pupal skin while the moth pulls itself out.

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Dorsal view of karamu leafminer, 'Acrocercops' zorionella, (Lepidoptera: Gracillariidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15XK]

Ventral view of karamu leafminer, 'Acrocercops' zorionella, (Lepidoptera: Gracillariidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15XH]

Photograph of a pinned moth of karamu leafminer, 'Acrocercops' zorionella, (Lepidoptera: Gracillariidae). Creator: M.N. Watt. © Transactions and Proceedings of the New Zealand Institute 1920 (1919) 52: 439–466, Plate XXX, fig. 2. [Image: 15XY]

Egg shell and leaf mine of the karamu leafminer, 'Acrocercops' zorionella, (Lepidoptera: Gracillariidae), on a leaf of Coprosma arborea (Rubiaceae), the shiny egg shell is by the midrib of the leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15XV]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), on a leaf of Coprosma arborea (Rubiaceae), the mine starts on the underside of the leaf and the caterpillar then tunnels through the leaf to form the rest of the mine. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15XW]

Karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), larva feeding in a leaf of Coprosma robusta (Rubiaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15WZ]

Karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), larva feeding in a leaf of Coprosma robusta (Rubiaceae), note the jaws biting the internal tissue of the leaf. Creator: Tim Holmes. © Plant & Food Research. [Image: 15WY]

Karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), larva exposed by removing part of the top of the leaf mine in a leaf of Coprosma robusta (Rubiaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15X2]

Karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), larva removed from its mine in a leaf of Coprosma robusta (Rubiaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15X1]

Karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), larva exposed by removing part of the top of the leaf mine in a leaf of Coprosma robusta (Rubiaceae), the larva appears to have just moulted, the old head capsule is visible. Creator: Tim Holmes. © Plant & Food Research. [Image: 15X4]

Leaf mine in a leaf of Coprosma robusta (Rubiaceae) made by the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), the fold in the leaf surface indicates the presence of a cocoon in the mine. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15XU]

Pupa of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in mine in a leaf of Coprosma robusta (Rubiaceae), note the two hooks at the rear end of the pupa. Creator: Tim Holmes. © Plant & Food Research. [Image: 19EV]

Pupa of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a silken cocoon made in the mine in a leaf of Coprosma robusta (Rubiaceae), note the spike on the head that is used to break through the cocoon and leaf mine. Creator: Martin Heffer. © Plant & Food Research. [Image: 15XD]

Pupa of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a silken cocoon made in the mine in a leaf of Coprosma robusta (Rubiaceae), note the spike on the head that is used to break through the cocoon and leaf mine. Creator: Martin Heffer. © Plant & Food Research. [Image: 15XC]

Pupal skin of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), protruding through a hole in the leaf mine in Coprosma robusta (Rubiaceae), note the sharp spike on the apex of the head that is used to break through the cocoon and leaf skin. Creator: Martin Heffer. © Plant & Food Research. [Image: 15XE]

Pupa of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae). Creator: M.N. Watt. © Transactions and Proceedings of the New Zealand Institute 1920 (1919) 52: 439–466, figs 4–6. [Image: 15XZ]

Moths of this leafminer are similar in appearance to other moths in the genus that are also leafminers. The moths can be distinguished by the bluish reflections from the shiny forewings and the rather few silvery markings. The white markings in the Pseudopanax miners (i.e. 'Acrocercops' species) are more extensive and scattered.

This is the only moth that makes long serpentine mines in large leaved Coprosma species. The caterpillars of the karamu shoot borer, Tanaoctena dubia Philpott, 1931 (Lepidoptera: Yponomeutidae), make small mines in fleshy leaves of some species of Coprosma. While a weevil, Notinus cordipennis (Broun, 1915) (Coleoptera: Curculionidae) makes a blotch mine in small-leaved Coprosma species such as Coprosma foetidissima, a species that is also host to the coprosma leaf mining moth.

The presence of the moth in a habitat can be recognised by the presence of its leaf mine.

Dorsal view of karamu leafminer, 'Acrocercops' zorionella, (Lepidoptera: Gracillariidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15XI]

Karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae). Creator: DSIR Photographers. © Landcare Research. [Image: 29LM]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma macrocarpa (Rubiaceae), the crease in the mine is the site of the cocoon. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15YI]

Leaf mines of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma grandifolia (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WN]

Leaf mines of the karamu shoot borer, Tanaoctena dubia (Lepidoptera: Yponomeutidae), in leaves of Coprosma robusta (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WH]

Predators

No predators of this moth have been reported. However, birds and spiders are likely to prey on the moths.

Parasitoids

At least two kinds of tiny wasps (Hymenoptera) parasitize larvae of the karamu leafminer. In the summer, caterpillars are killed by a single larva of one of the wasp species. Before pupation this wasp larva builds columns of black faeces on either side of itself, so that the pupa has some protection from crushing. In the winter and spring leaf mines can be found with several white larvae or black pupae of a second wasp parasitoid. This wasp species may kill the caterpillar or the pupa.

Two leaf mines of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a leaf of Coprosma robusta (Rubiaceae), each mine contains one parasitoid (Hymenoptera) with columns of black faeces on either side and the remains of the caterpillar. Creator: Martin Heffer. © Plant & Food Research. [Image: 15XF]

White parasitoid larvae (Hymenoptera) exposed by removing the outer skin of a leaf mine of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a leaf of Coprosma robusta (Rubiaceae), note head capsule of the dead caterpillar. Creator: Martin Heffer. © Plant & Food Research. [Image: 15X7]

Black parasitoid pupae (Hymenoptera) exposed by removing the outer skin of a leaf mine of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a leaf of Coprosma robusta (Rubiaceae), note head capsule of the dead caterpillar. Creator: Martin Heffer. © Plant & Food Research. [Image: 15X6]

Exit holes made by parasitoids (Hymenoptera) in a leaf mine of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a leaf of Coprosma robusta (Rubiaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15X9]

A cocoon of a karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), dissected to show the dead pupa and empty pupal skins of a parasitic wasp (centre of image). Creator: Tim Holmes. © Plant & Food Research. [Image: 15XA]

Adult parasitoid (Hymenoptera) of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), top side of wasp that has several larvae in caterpillar. Creator: Tim Holmes. © Plant & Food Research. [Image: 15XM]

Adult parasitoid (Hymenoptera) of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), top side of wasp that has several larvae in caterpillar. Creator: Tim Holmes. © Plant & Food Research. [Image: 15XR]

Adult parasitoid (Hymenoptera) of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), top side of wasp that has several larvae in caterpillar. Creator: Tim Holmes. © Plant & Food Research. [Image: 15XP]

Side view of adult parasitoid (Hymenoptera) of karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae); this wasp species has several larvae in caterpillar. Creator: Tim Holmes. © Plant & Food Research. [Image: 15XS]

The karamu leafminer forms leaf mines in species of Coprosma (Rubiaceae), with large and medium sized leaves. Mines are more commonly found in very young plants and saplings of broad leaved Coprosma species growing alongside forest tracks.

The caterpillars feed on the internal tissues of the leaf. They tunnel through making mines that are visible from the upper side of the leaf.

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma tenuifolia (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WR]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma tenuifolia (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WS]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma rotundifolia (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WX]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma arborea (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15XG]

Leaf mines of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in leaves of Coprosma lucida (Rubiaceae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 15XX]

Leaf mines of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma grandifolia (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WN]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma grandifolia (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15WP]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma macrocarpa (Rubiaceae), the crease in the mine is the site of the cocoon. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15YI]

Underside of leaf of Coprosma macrocarpa (Rubiaceae) with the start of a leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 15YJ]

Leaf mines of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in a leaf of Coprosma macrocarpa (Rubiaceae). Creator: Minna Personen. © Plant & Food Research. [Image: 1ITP]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), in Coprosma foetidissima (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 29LK]

Leaf mine of the karamu leafminer, ‘Acrocercops’ zorionella, (Lepidoptera: Gracillariidae), on a leaf of Coprosma areolate (Rubiaceae), the mine starts on the underside of the leaf (right) and the caterpillar then tunnels through the leaf to form the rest of the mine (left). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2KK1]

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.

Watt MN 1920 (1919). The leaf mining insects of New Zealand. Transactions and Proceedings of the New Zealand Institute 52: 439-466.

Robert Hoare for information about this moth.

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

1 July 2018. NA Martin. Remove Coprosma repens as host plant and photo of leaf mine.

1 August 2017. NA Martin. Host plant table updated and photo of another host plant added.