INTERESTING INSECTS

By N A Martin (2018)

Collyer's tetranychid mite

This endemic spidermite was described and named in 1967. It is mainly found on a small selection of small trees and shrubs. It is on plants in city gardens and parks as well as native ecosystems.

Conservation status: Widespread, not threatened.

Life stages of Tetranychus mites. Creator: Crop & Food Research. © based on figure 21 in Crop & Food Research Broadsheet 112. [Image: 2HRR]

These mites are very small and live in colonies on the underside of young leaves. Adult female mites are about 0.42 mm long and about 0.33 mm wide. Adult males are slightly smaller and have a pointed end to their abdomen. The summer breeding adult females are a deep red or carmine. All active stages may have a darker area on each side of the abdomen. The four pairs of legs are whitish or tinted orange. Adult female mites lay pale brown spherical eggs on the underside of leaves, often by the midrib. The larva that hatches from an egg looks like a tiny adult, but only has three pairs of legs and lacks the reddish colour and has dark spots on the abdomen. The mite larva moults (changes skin) into a nymph which has four pairs of legs like the adult. The first nymphal stage moults into a second nymph. Both nymphal stages are red coloured. The last juvenile stage moults into an adult mite. Adult males mate with newly emerged adult females. The species overwinters as dormant female mites hiding away from the plant leaves.

Feeding

The mites have pointed mouth parts that puncture the surface cells of leaves. They suck out the contents of the cells. The black areas in the abdomen are part of their gut where the plant cell contents are digested.

Walking and web spinning

The mite uses its legs for walking. As they walk they produce a web from their abdomen which is attached to the leaf surface. When a dense colony forms the surface of the leaf becomes covered by webbing.

Dispersal to new leaves and new plants

When a dense colony develops or a plant leaf is no longer suitable, mites may walk to another leaf on the same branch or a nearby branch. Spidermites are also dispersed by wind. Mated female mites will climb to the top of the plant produce a strand of silk and stand waiting for a gust of wind to take them away. The mites form new colonies on the underside leaves. New colonies are often formed where there is some shelter, such as a hollow in the leaf or by the midrib.

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQY]

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae): note the pale area on the leaf where the mites have been feeding. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQX]

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RR0]

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae): note the white moulted larval skins (bottom left). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQZ]

Hatched and unhatched eggs of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQV]

Unhatched eggs and nymphs of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the white moulted skins of the larvae. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQN]

Eggs and mites of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the small larvae with two spots (top right). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQR]

Eggs and mites of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQS]

Eggs and mites of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the small larvae with two spots. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQT]

Eggs and mites of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the small larvae with two spots (top right). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQU]

This mite requires special procedures and taxonomic knowledge to identify specimens. However, where it is the only species of spidermite known to live on a host plant, it can be identified by its distinctive damage to leaves and the red colour of the mites. Also if two species are known to live on a host plant and the breeding adult females have a different body colour, the colonies can be identified.

On one plant, Mahoe, Melicytus ramiflorus, two species of spidermites have been found living on the leaves. The summer breeding females of Collyer's tetranychid mites are red, whereas those of the banana mite, Tetranychus lambi Pritchard & Baker, 1955, are green.

Two species of Tetranychus are known to live on another native plant, North Island broom, Carmichaelia australis. Unfortunately, the appearance of living Tetranychus eyrewellensis Manson, 1967 has not been described, so live colonies of the two species cannot be distinguished and the mites examined by a taxonomist.

Where only one species of spider mite known on a host plant, its presence can be recognised by its presence in colonies of the mites on its host plants and the pale areas on the leaves caused by mite feeding.

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQY]

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RR0]

Underside of a leaf of Coastal Coprosma Coprosma repens (Rubiaceae) with yellowing due to feeding by a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RR5]

Leaf of Coastal Coprosma Coprosma repens (Rubiaceae) with yellowing due to feeding by a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RR4]

Predators

At least three kinds of predators have been found associated with Collyer's tetranychid mites. These are ladybirds, predatory mites and predatory fly larvae. It is likely that they are also fed on by adults and nymphs of predatory sucking bugs (Hemiptera).

The name of only one of the two predatory mites is known. Phytoseiulus persimilis (Acari: Mesostigmata: Phytoseiidae). This predatory mite comes from Southern Europe and was imported into New Zealand to assist control of two-spotted mite, Tetranychus urticae (Acari: Tetranychidae), a pest of greenhouse and outdoor crops. Adult female Phytoseiulus persimilis are bright red and larger than flax spidermites. They lay larger oval red eggs. It’s larvae, nymphs and adult males are also red.

Several species of spidermite feeding ladybirds, Stethorus (Coleoptera: Coccinellidae), are present in New Zealand. The name of those that eat Collyer’s tetranychid mites are not yet known. The adults are tiny and black. Oval eggs, white, tan or reddish are laid in mite colonies. The larvae may be white, white with dark spots or dark grey. The pupae are black.

Some fly larvae in the family Cecidomyiidae are known predators of spider mites. Larvae of an unknown species were found feeding on Collyer's tetranychid mites.

Red fly larvae of a predatory cecidomyiid (Diptera: Cecidomyiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). © All rights reserved. [Image: 2RQ2]

Red fly larva of a predatory cecidomyiid (Diptera: Cecidomyiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). © All rights reserved. [Image: 2RQ1]

Red fly larva of a predatory cecidomyiid (Diptera: Cecidomyiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). © All rights reserved. [Image: 2RQ3]

Nymph of a predatory phytosiid mite (Acari: Phytoseiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). © All rights reserved. [Image: 2RQ4]

A large predatory phytosiid mite (Acari: Phytoseiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). © All rights reserved. [Image: 2RQ5]

A large predatory phytosiid mite (Acari: Phytoseiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). © All rights reserved. [Image: 2RQ6]

A large predatory phytosiid mite (Acari: Phytoseiidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coastal Coprosma, Coprosma repens (Rubiaceae). © All rights reserved. [Image: 2RQ7]

An adult Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQ8]

Side view of an adult Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the setae (hairs) covering the ladybird. Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQ9]

A pale larva of a Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). © All rights reserved. [Image: 2RQC]

Pupae and one mature brown larva of a Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2RQD]

Pupa of a Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2RQA]

Side view of a pupa of a Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Minna Personen. © Plant & Food Research. [Image: 2RQB]

Pupal skins of a Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2RQF]

Pupal skin and just emerged adult of a Spidermite ladybird, Stethorus sp. (Coleoptera: Coccinellidae) in a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2RQE]

Collyer's tetranychid mites are found on the underside of leaves of host plants that are mainly shrubs and trees. The mites have pointed mouth parts that puncture the surface cells of flax leaves. They suck the contents of the cells. Feeding removes the green cell contents. The presence of old and active mite colonies can be recognised by the pale yellow colour of the leaf in and around mite colonies. The mites also cover the surface of the leaf with silk webbing.

Underside of a leaf of Putaputawētā, Carpodetus serratus (Rousseaceae) with a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQI]

Underside of a leaf of Ngaio, Myoporum laetum (Scrophulariaceae) with a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae): note the eggs by the midrib. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQM]

Leaf of Coprosma macrocarpa subsp. minor (Rubiaceae) with yellowing due to a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQJ]

Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside of a leaf of Coprosma macrocarpa subsp. minor (Rubiaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQK]

Leaf of Coprosma macrocarpa subsp. minor (Rubiaceae) with yellowing due to a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQL]

Underside of a leaf of Coastal Coprosma Coprosma repens (Rubiaceae) with yellowing due feeding by a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RR1]

Leaf of Coastal Coprosma Coprosma repens (Rubiaceae) with yellowing due to feeding by a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae) on the underside. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RR3]

Underside of a leaf of Coastal Coprosma Coprosma repens (Rubiaceae) with yellowing due feeding by a colony of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQW]

Underside of leaves of Mahoe, Melicytus ramiflorus (Violaceae) with yellowing and pale areas due to feeding by Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQH]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with yellowing due to a colonies of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2RQG]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with pale areas due to a colonies of Collyer's tetranychid mites, Tetranychus collyerae (Acari: Tetranychidae): note that the pale areas are in hollows. Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2RR6]

Occasionally large colonies of Collyer's tetranychid mite develop on the underside of leaves of host plants in native ecosystems as well as plants in modified environments such as gardens and parks. These colonies do not appear to weaken plants. Predatory mites, tiny ladybirds and larvae of predatory flies will control populations.

Dr Elsie Collyer was a British scientist who studied mites in England and New Zealand. She was a pioneer in the development of biological control and integrated pest management (IPM). Her career began at the East Malling Research Station in England where she studied the effects of pesticides on the natural enemies of pests in apple orchards, most notably the effect of DDT killing Typhlodromus pyri and other predators of European red mite. She became an international authority in this area of practical science. Her research paved the way for ‘Integrated Mite Control’ in New Zealand and other countries. These early studies also initiated her lifelong interest in mites and biological control.

A National Research Fellowship, 1959-1961, brought Elsie to New Zealand. She was based in Auckland with Plant Diseases and Fruit Research Divisions of DSIR. She made the first studies of ‘Integrated Control’ in New Zealand apple orchards. As a result of their success, she returned to New Zealand in 1964 when she joined Entomology Division of DSIR in Nelson. She was the science leader of the ‘Integrated Pest Control’ programme being developed by the three DSIR Divisions but decided to resign and remain in Nelson when Entomology Division transferred its headquarters to Auckland in 1973. She continued to contribute to the research programme under contract and integrated pest control eventually developed into the IPM programme for apple orchards we see in use today.

Elsie also continued her interest in the taxonomy of mites and made important contributions in several families including Acaridae, Tenuipalpidae, Tuckerellidae and Phytoseiidae. Elsie had a great sense of humour. For example, she liked her drink, so when she needed a name for a species of Phytoseiidae, she was delighted to be able to name it after the person who had collected it; hence, Amblyseius martini (Collyer, 1982).

After she married, Dr Elsie Ashley continued to use her maiden name for her scientific publications.

Manson DCM. 1967. The spider mite family Tetranychidae in New Zealand. II The genus Tetranychus. Acarologia. 9: 581-597.

Manson DCM. 1967. The spider mite family Tetranychidae in New Zealand. IV Two new species of Tetranychus and a revised key to the genus. New Zealand Journal of Science. 10: 1083-1091.

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

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 and information about Dr Elsie Collyer after whom the mite is named.