Titoki moth - Vanicela disjunctella
By N A Martin (2017)
Biostatus and Distribution
This endemic moth is found throughout New Zealand on its host plant, titoki, Alectryon excelsus (Sapindaceae). Its distinctive basket weave cocoons may be found in the fold of leaves of titoki and plants growing under titoki trees.
Conservation status: Widespread in native ecosystems, parks and street trees, not threatened.
Life Stages and Annual Cycle
There are probably two or more generations per year, though this may depend on the presence of expanding young leaves on which the caterpillars feed. The moths fly from October to April.
The moths are about 8-10 mm long with a distinctive black and white colouring on top and white underside. At rest, the black wings are folded tightly along the body. In contrast the head, thorax and legs are white. The long hairy antennae are held against the body, while the white labial palps curve in front of the head. There have been no reports of moths mating. It is assumed that the newly emerged female moth emits a pheromone (a mixture of volatile chemicals), that attracts the male moth. Male moths have feathery antennae that have a large number of sensory cells for detecting chemicals in the air.
The female moth lays single eggs on the underside of young expanding leaves of titoki. The caterpillar upon hatching from the egg chews through the egg shell into the leaf and tunnels into the leaf forming a serpentine leaf mine. Older caterpillars live on the young leaves rolling their edge to form shelters. The older caterpillars are green and have three pairs of true legs and five pairs of pseudopods (false legs). The caterpillars grow by changing skins, moulting. The older caterpillars feed by chewing large areas of young leaves. Fully grown caterpillars are about 8-10 mm long.
Cocoon and pupa. When the caterpillar is fully grown, it finds a hollow on the underside of a leaf and weaves a distinctive cocoon. The outer surface looks like woven cloth with wide spacing between both the weft and warp. Under this, is a loosely woven oval cocoon in which the caterpillar lies prior to moulting into the pupa. Cocoons may be formed on the underside of leaves of both titoki trees and plants living below titoki trees. The pupa is pale green with four pairs of small dark spots on the underside. When the moth is ready to emerge, the pupa wriggles forward through the inner cocoon and the front sticks out the basket weave structure. After moths emerge from their pupae, they crawl to a suitable place from which to hang. They expand their wings and then let them harden and dry.
Adult moths have a distinctive appearance, though they are small and cryptic. The narrow shape is formed by the black wings held tightly against the body. In contrast is the white thorax and head with the palps curved in front.
The green caterpillars are the only species of non-looper (Geometridae) caterpillars feeding on young leaves that does not web leaves together. However, it can be difficult to see on leaves. The leaf mines are also diagnostic of the species, but the most distinctive feature is the cocoon with its white basket weave. They can be found on the underside of leaves where there is a hollow. The leaf mines and the cocoons are indicative of the presence of the moth.
Predators. No predators of titoki moth adults or caterpillars have been recorded. It is likely that insect predators feed on the caterpillars as well as birds. Birds and spiders probably also catch moths.
Pathogen. No pathogens of this insect are known.
One fly and seven wasp parasitoids have been reared from titoki moth caterpillars and pupae. Two of the wasps are hyperparasitioids, that is parasitoids of parasitoids. The fly, Trigonospila brevifacies (Diptera: Tachinidae) was released into New Zealand to provide biological control for leafroller caterpillars (Tortricidae) in orchards. The basket-cocoon wasp, Meteorus pulchricornis (Hymenoptera: Braconidae) is a recent arrival in New Zealand. It parasitises small to medium sized caterpillars. Its distinctive cocoon dangles by a thread. One wasp, Proacrias n.sp. is a parasitoid of moth and fly larvae that live in leaf mines.
The two hyperparasitoids are Mesochorus sp. 1 (Ichneumonidae) and Pediobius bruchicida (Eulophidae).
|Scientific Name||Common Name||Classification||Enemy Type||Reliability Index||Biostatus|
|Diadegma sp. 1 of Ward 2016||(Wasp)||Hymenoptera: Ichneumonidae||parasitoid||7||unknown|
|Dolichogenidea sp.||(Wasp)||Hymenoptera: Braconidae||parasitoid||7||endemic|
|Mesochorus sp. 1 of Ward 2016||(Wasp)||Hymenoptera: Ichneumonidae||parasitoid||7||unknown|
|Meteorus pulchricornis (Wesmael, 1835)||Basket-cocoon wasp (Wasp)||Hymenoptera: Braconidae||parasitoid||10||adventive|
|Pediobius bruchicida (Rondani, 1872)||(Wasp)||Hymenoptera: Eulophidae||parasitoid||8||adventive|
|Proacrias n.sp. (J. Berry 2001)||(Wasp)||Hymenoptera: Eulophidae||parasitoid||7||endemic|
|Trigonospila brevifacies (Hardy, 1934||Australian leafroller tachinid (Fly)||Diptera: Tachinidae||parasitoid||10||adventive|
|Zealachertus tortriciphaga Berry, 1999||(Wasp)||Hymenoptera: Eulophidae||parasitoid||8||endemic|
The Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), caterpillars only feed on titoki Alectryon excelsus (Sapindaceae). The young caterpillars tunnel in young leaves forming serpentine mines. Older caterpillars hide in rolled edges of leaves and chew young leaves creating ragged edges.
Dugdale JS. 1975. Insects: plume moths and leaf miners. New Zealand Natural Heritage. 4 (53): 1469-1474.
Robert Hoare for information about the moth.
The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.