INTERESTING INSECTS

By N A Martin (2017)

Titoki moth

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.

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.

Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), upper side of moth. Creator: Tim Holmes. © Plant & Food Research. [Image: 2EG9]

Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), underside of moth. Creator: Tim Holmes. © Plant & Food Research. [Image: 2EGA]

Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), underside of moth. Creator: Tim Holmes. © Plant & Food Research. [Image: 2EGB]

Egg shell and leaf mine of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFH]

Caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFZ]

Leaves of titoki, Alectryon excelsus (Sapindaceae) with feeding damage and edges rolled by caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFW]

Leaflet of titoki, Alectryon excelsus (Sapindaceae) with edges pulled together by a cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EG6]

Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFI]

Caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), exposed in cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFR]

Close up of edge of cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EG4]

Close up of outer layer of cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EG5]

Dorsal side of pupa of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), exposed in cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFQ]

Dorsal side of pupa of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), exposed in cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFP]

Pupa of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), in cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFD]

Pupal case of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), half out of cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EG0]

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.

Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), upper side of moth. Creator: Tim Holmes. © Plant & Food Research. [Image: 2EG9]

Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFI]

Dorsal side of pupa of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), exposed in cocoon on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFP]

Green caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFY]

Leaf mine made by young caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), in leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFG]

Leaves of titoki, Alectryon excelsus (Sapindaceae) with feeding damage and edges rolled by caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFT]

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.

Parasitoids.

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).

Parasitic wasp (Hymenoptera) cocoon in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFK]

Parasitic wasp (Hymenoptera) in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFN]

Parasitic wasp (Hymenoptera) cocoon in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae), note the exit holes for the adult wasp in both cocoons. Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFL]

Parasitic wasp (Hymenoptera) cocoon exposed in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), note the exit hole for the adult wasp. Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFM]

Dorsal (upper side) of adult parasitic wasp (Hymenoptera) of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EGR]

Ventral (underside) of adult parasitic wasp (Hymenoptera) of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2EFS]

Cocoon of basket-cocoon wasp, Meteorus pulchricornis (Hymenoptera: Braconidae) suspended by a thread from cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae), note the dead caterpillar in the cocoon. © All rights reserved. [Image: 2EEU]

Cocoon of basket-cocoon wasp, Meteorus pulchricornis (Hymenoptera: Braconidae) suspended by a thread from cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), on underside of leaf of titoki, Alectryon excelsus (Sapindaceae). © All rights reserved. [Image: 2EEV]

Adult basket-cocoon wasp, Meteorus pulchricornis (Hymenoptera: Braconidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2ER3]

Underside of adult basket-cocoon wasp, Meteorus pulchricornis (Hymenoptera: Braconidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2ER2]

Cocoon of parasitoid wasp, Dolichogenidea sp. (Hymenoptera: Braconidae) in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EEN]

Cocoon of parasitoid wasp, Dolichogenidea sp. (Hymenoptera: Braconidae) exposed in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EEP]

Dead adult parasitoid wasp, Dolichogenidea sp. (Hymenoptera: Braconidae) of caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EEQ]

Dead adult parasitoid wasp, Dolichogenidea sp. (Hymenoptera: Braconidae) of caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EER]

Brown cocoon of parasitoid wasp, Mesochorus sp. (Hymenoptera: Ichneumonidae), a hyperparasitoid of parasitised caterpillars in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EET]

Dead adult parasitoid wasp, Mesochorus sp. (Hymenoptera: Ichneumonidae), a hyperparasitoid of parasitised caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EES]

Dead adult parasitoid wasp, Pediobius bruchicida (Hymenoptera: Eulophidae), a hyperparasitoid of parasitised caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EEW]

Dead adult parasitoid wasp, Pediobius bruchicida (Hymenoptera: Eulophidae), a hyperparasitoid of parasitised caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EEY]

Pupa of a wasp that is a parasitoid of small caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EGC]

Pupa of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae) exposed in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). © All rights reserved. [Image: 2EF7]

Pupa of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae). © All rights reserved. [Image: 2EF8]

Pupa of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae) exposed in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), note the exit hole of the fly. © All rights reserved. [Image: 2EF5]

Upper side of adult of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae). © All rights reserved. [Image: 2EFA]

Underside of adult of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae). © All rights reserved. [Image: 2EF9]

Adult of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae). © All rights reserved. [Image: 2EFC]

Pupa of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae) exposed in cocoon of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), note the exit hole of the fly. © All rights reserved. [Image: 2EF6]

Adult of Australian leafroller tachinid, Trigonospila brevifacies (Diptera: Tachinidae). © All rights reserved. [Image: 2EFB]

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.

Leaf mine made by young caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), in leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFF]

Leaf mine made by young caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), in leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFE]

Leaf mine made by young caterpillar of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae), in leaf of titoki, Alectryon excelsus (Sapindaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFV]

Leaves of titoki, Alectryon excelsus (Sapindaceae) with feeding damage and edges rolled by caterpillars of Titoki moth, Vanicela disjunctella (Lepidoptera: Roeslerstammiidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2EFW]

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.