Phytomyza clematadi Watt, 1923
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.
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.
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.
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.
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.
There are no reports of predators of the flies, but it is likely that they are preyed upon by birds, spiders and predatory insects.
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.
|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|
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.
|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|
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.
The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.
1 December 2018. NA Martin. Changed symbol used for apostrophes.