Clematis leafminer - Phytomyza clematadi

By N A Martin (2018)

Caption:

Classification

Phylum

Arthropoda

Class

Insecta

Order

Diptera

Family

Agromyzidae

Scientific name

Phytomyza clematadi Watt, 1923

Common names

Clematis leafminer

Biostatus and distribution

This endemic leaf mining fly is found throughout New Zealand where its host plants, native Clematis species (Ranunculaceae), are found. The fly is found in native ecosystems as well as gardens and parks. It may sometimes be found on non-native species of Clematis.

Conservation status: Widespread, not threatened.

Life stages and annual cycle

The fly appears to breed when young foliage is on the vines. Leaf mines have been found from August through to April.

Adult fly

The flies are small, about 3 mm long, similar to the size of vinegar flies, Drosophila species, that are seen around rotting fruit. The body is grey-black with pale areas. The three pairs of legs and the pair of knob-like antennae are pale brown. Like all flies, they have one pair of wings behind which are a pair of small knobs, or halteres that help the fly to balance during flight. The male has rounded black external genitalia at the end of the abdomen, while the female has a more tubular end that contains an ovipositor. The ovipositor is used to make holes in young leaves into which eggs are laid. Females of other species of this kind of leaf-mining fly also make holes with their ovipositor and feed on the leaf sap. This has not been observed for the Clematis leafminer.

Eggs and larvae

Single eggs are inserted into young leaves. The newly hatched larvae tunnel into the leaf making a mine that is visible on the upper side of the leaf. The larvae feed on the internal cells of the leaf. They have a single black jaw that is moved from side-to-side, scraping the plant cells at the head of the mine. The plant cells are ingested and the dark green faeces excreted into the mine behind it in the centre of the mine or to one side. The larva moults, or changes skin, as it gets larger. There are three larval stages (instars). A fully grown larva is about 3 mm long. The mine meanders over the leaf. It is narrow at first, gradually widening.

Pupa

When fully grown the larva makes a chamber at the end of the mine in which it pupates. The larva pupates inside its larval skin, which turns brown and hard. This structure is called a puparium. The puparium has a pair of stigma (organs for breathing) at each end of the body. The stigma at the front end of the body are pushed through the upper skin of the leaf. After several weeks, the eyes and bristles of the adult fly can be seen through the skin of the puparium.

Fly emergence

When ready to emerge, part of the head, just above the antennae, balloons out. This structure, the ptilinum, pushes the front of the pupa open. There is a line of weakness between the top and bottom halves of the first three and a half segments that splits allowing the top to be pushed through the skin of the leaf. The fly crawls out of the puparium onto the surface of the leaf. After the fly has crawled out, the ptilinum retracts into the head. The fly wings expand and the body hardens. Over the next 12 hours the fly acquires its full body colour.

It is not known how the male and females find each other for mating.

Side view of a female Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ5]

Front view of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ7]

Rear view of a male Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ9]

Underside of a female Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ6]

Underside of a male Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZA]

A leaflet of White clematis, Clematis paniculata (Ranunculaceae), with a leaf mine made by the larva of the Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZP]

Larva of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) exposed in its leaf mine. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ2]

Larva of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) exposed in its leaf mine. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ3]

Larva of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) exposed in its leaf mine: note the black jaw at the front for scraping plant tissue into its mouth. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ1]

Puparium of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) exposed in its leaf mine. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZC]

Stigma (breathing tubes) of a puparium of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) protruding through the skin (epidermis) of its leaf mine. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZD]

Top of the front of a puparium of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) breaking the skin (epidermis) of the leaf mine to enable the adult fly to leave the puparium. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZF]

A puparium of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) after the adult fly has emerged: note the front (right) of the antennae is slightly raised. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ8]

Recognition

These small flies require expert knowledge for identification. However, the presence of the species can be detected by the leaf mines. However, a second species of leaf miner fly of Clematis has been present in New Zealand since summer 1996/97 when the Old man's beard leafminer, Phytomyza vitalbae Kaltenbach, 1874, was released for the biological control of old man's beard, Clematis vitalba. While this species is mainly found on Old man's beard, it sometimes infests other species of Clematis.

Superficially, the leaf mines of the two species of fly are similar, but the Clematis leaf miner pupates in the leaf, while the larva of the Old man's beard leaf miner leaves the mine and pupates in the litter or soil.

Careful examination of a mined leaf can show if a pupa is present with its opening on the upper side of the leaf or if the mine has a larval exit slit cut on the underside of the leaf.

Leaves of White clematis, Clematis paniculata (Ranunculaceae), with leaf mines made by the larva of the Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZQ]

A leaf of clematis, Clematis sp. (Ranunculaceae), with leaf mines made by the larva of the Old man's beard leafminer Phytomyza vitalbae (Diptera: Agromyzidae): note the adult feeding punctures on one leaflet. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZS]

A leaflet of clematis, Clematis sp. (Ranunculaceae), with leaf mines made by the larvae of the Old man's beard leafminer Phytomyza vitalbae (Diptera: Agromyzidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZU]

The underside of a leaflet of clematis, Clematis sp. (Ranunculaceae), with leaf mines made by the larvae of the Old man's beard leafminer Phytomyza vitalbae (Diptera: Agromyzidae): note the two exit slits made mature larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZV]

The underside of a leaflet of clematis, Clematis sp. (Ranunculaceae), with a leaf mine and an exit slit made by a larva of the Old man's beard leafminer Phytomyza vitalbae (Diptera: Agromyzidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZX]

Natural enemies

Predators

There are no reports of predators of the flies, but it is likely that they are preyed upon by birds, spiders and predatory insects.

Parasitoids

Three species of parasitoids have been reared from the Clematis leafminer. The adult female wasp usually lays an egg in the fly larva. The wasp larva feeds on the live fly larva. Some wasp larvae, such as Opius species, kill the fly after it has pupated, while others kill the fly larva before pupation. Some of the latter group of wasp larvae pupate within the fly larval skin, while others leave the larval skin before pupating.

Three images of an adult wasp (Hymenoptera) parasitoid of Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). The image on the right shows the underside of the wasp. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZB]

Dead larva of Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) killed by a wasp (Hymenoptera) parasitoid. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZH]

Dead larva of Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) killed by a wasp (Hymenoptera) parasitoid. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZI]

Two images of a dead larva of Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) with a pupa of a wasp (Hymenoptera) parasitoid: note the dark pillars on either side of the pupa. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZJ]

Table: Natural enemies of Clematis leafminer, *Phytomyza clematadi* (Diptera: Agromyzidae), from Plant-SyNZ database (26 June 2018). The reliability index shows the quality of evidence for the host association (0-10, 10=high quality).
Scientific Name	Common Name	Classification	Enemy Type	Reliability Index	Biostatus
Chrysonotomyia sp. 'Agromyzidae' of Berry 2000	(Wasp)	Hymenoptera: Eulophidae	parasitoid	7	endemic
Noyesius testaceus Boucek, 1988	(Wasp)	Hymenoptera: Eulophidae	parasitoid	10	endemic
Opius sp. 6 of Berry 2000	(Wasp)	Hymenoptera: Braconidae	parasitoid	8	unknown

Host plants

The Clematis leafminer makes leaf mines in native and non-native species of Clematis (Ranunculaceae). The adult female fly makes small punctures in young leaves for egg-laying and possibly for feeding. The larva burrows through the leaf making mines that are visible from the upper side of the leaf. The mine gradually gets wider and makes a serpentine pattern. In a leaf infested with many larvae most of the green tissue can be removed from the leaf.

A leaf of Small white clematis, Clematis forsteri (Ranunculaceae), with a leaf mine made by the larva of the Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZN]

A leaflet of Small white clematis, Clematis forsteri (Ranunculaceae), with a leaf mine made by the larva of the Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RZL]

Table: Host plants of the Clematis leafminer, *Phytomyza clematadi* (Diptera: Agromyzidae) from Plant-SyNZ database (26 June 2018). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)	Scientific Name	Family	Reliability Index	Biostatus
	Clematis dioscoreifolia (Lev. and Vaniot) Rehd. var. robusta (Carr.) Rehd.	Ranunculaceae	6	cultivated
	Clematis foetida Raoul	Ranunculaceae	10	endemic
Small white clematis, Pikiarero, Poananga, Pōhue, Pōhuehue, Pōpōhue, Puatataua, Puataua, Puatautaua, Puawānanga, Puawhānanga	Clematis forsteri J.F.Gmel.	Ranunculaceae	8	endemic
White clematis, Pikiarero, Pohue, Popokonui-a-hura, Pūānanga, Puapua, Puatataua, Puataua, Puatauataua, Puawānanga	Clematis paniculata J.F.Gmel.	Ranunculaceae	10	endemic
Old man's beard, Travellers joy	Clematis vitalba L.	Ranunculaceae	6	naturalised

Information sources

Hill RL, Wittenberg R, Goulay AH. 2001. Biology and host range of Phytomyza vitalbae and its establishment for biological control of Clematis vitalba in New Zealand. Biocontrol Science and Technology. 11: 459-473.

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

Spencer KA 1976. The Agromyzidae of New Zealand (Insecta: Diptera). Journal of the Royal Society of New Zealand 6(2): 153-211.

Watt MN 1923. The leaf-mining insects of New Zealand: part III - species belonging to the genus Agromyza (Fallen) and Phytomyza (Fallen). Transactions and Proceedings of the New Zealand Institute 54: 465-489.

Acknowledgements

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

Other images

Two views of the stigma (breathing tubes) of a puparium of a Clematis leafminer Phytomyza clematadi (Diptera: Agromyzidae) protruding through the skin (epidermis) of its leaf mine. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RZ4]

Update history

1 December 2018. NA Martin. Changed symbol used for apostrophes.

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