Acalitus cottieri (Lamb, 1952)
Coprosma bud gall mite, Coprosma bud mite
Aceria cottieri Lamb, 1952
Acalitus tenuis Manson, 1970
Biostatus and distribution
This endemic gall mite is found in the North and South Islands of New Zealand on its host plants, Coprosma species (Rubiaceae). Feeding by the mites induces galls in places such as flower/fruit buds and clusters of vegetative buds. The mite appears to be scarce in the Auckland Region, but its gall are seen more frequently south of Auckland.
Conservation status: Widespread, not threatened.
Life stages and annual cycle
This gall mite is very tiny. Adult mites are about 0.108-0.168 mm long. The adult mite is like a tiny white cow's horn with two pairs of legs at the wide end of the horn. Adult female mites lay tiny spherical eggs. The larva that hatches from an egg looks like a tiny adult. The mite larva moults (changes skin) into a nymph. There is one nymphal stage that also looks like a small adult. The last juvenile stage moults into an adult mite. There are males and females.
The mite uses its legs for walking, but it can also hold on to the plant with the tip of its abdomen, which acts as a sucker.
Feeding and inducing the gall
The mites have pointed mouth parts that puncture the surface cells of young leaves and gall tissue from which they suck up the cell sap. During feeding, the mites may inject saliva into the plant. When mites feed in a bud, the plant cells in the immediate area multiply forming a hairy spongy tissue in which the mites live and breed. The buds also grow bigger forming a large gall. The gall has spaces in which the mites live and it protects the gall mites from predators and adverse weather.
Dispersal to new stems and new plants
When the plant grows new shoots, adult female mites disperse to these and their feeding induces the formation of new galls. It is presumed that mites walk from the old galls to young plant growth suitable for the initiation of new galls.
When this gall mite colonises new plants or branches, it is unlikely that mites walk all the way. It is believed that most mites are dispersed by wind. Some species of mite climb to prominent places on plants and stand waiting for a gust of wind to take them away.
This mite requires special procedures and taxonomic knowledge to identify specimens. However, its presence on a plant can be recognised by plant damage symptoms. This species of mite is the only one known to induce bud galls on Coprosma species (Rubiaceae) in New Zealand. Bud galls on other species of plant are caused by other species of mite or by insects.
No natural enemies of this mite have been recorded, but predatory mites may feed on these mites.
The Coprosma bud gall mite is found on large and small leaved Coprosma species (Rubiaceae)
Feeding by the mites induces galls in places such as flower/fruit buds and clusters of vegetative buds. The plant tissue in the buds grows larger and creates spaces between parts of the enlarged buds in which the mites live. Vegetative buds may be induced to produce a mass of leaves or stems, the latter are often called a 'witches broom'.
|Common Name(s)||Scientific Name||Family||Reliability Index||Biostatus|
|Coprosma ×cunninghamii Hook.f.||Rubiaceae||10||endemic|
|Coprosma aff. parviflora||Rubiaceae||10||endemic|
|Thin leaved coprosma, Aruhe||Coprosma areolata Cheeseman||Rubiaceae||10||endemic|
|Coprosma colensoi Hook.f.||Rubiaceae||10||endemic|
|Coprosma cuneata Hook.f.||Rubiaceae||10||endemic|
|Coprosma dumosa (Cheeseman) G.T.Jane||Rubiaceae||10||endemic|
|Yellow wood, Mikimiki||Coprosma linariifolia Hook.f.||Rubiaceae||10||endemic|
|Coprosma linariifolia x parviflora||Rubiaceae||10||endemic|
|Leafy coprosma||Coprosma parviflora Hook.f.||Rubiaceae||10||endemic|
|Miki, Mingi, Mingimingi||Coprosma propinqua A.Cunn. var. propinqua A. Cunn.||Rubiaceae||10||endemic|
|Coprosma pseudocuneata W.R.B.Oliv. ex Garn.-Jones & Elder||Rubiaceae||10||endemic|
|Twiggy Coprosma||Coprosma rhamnoides A.Cunn.||Rubiaceae||10||endemic|
|Glossy karamu, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū||Coprosma robusta Raoul||Rubiaceae||10||endemic|
|Swamp comprosma, Hukihuki||Coprosma tenuicaulis Hook.f.||Rubiaceae||10||endemic|
Eriophyid gall mites belong to the super family Eryiophyoidea. These mites have several unusual features. For example, though most mites have four pairs of legs like spiders, Eriophyoid mites have only two pairs of legs. Many of these mites can induce host plants to form galls, some of which may be very complex. Some species of these mites can transmit plant viruses that may cause plant diseases and plant death.
Manson DCM 1984. Eriophyinae (Arachnida: Acari: Eriophyoidea). Fauna of New Zealand 5: 1-123.
The New Zealand Plant & Food Research Institute Limited (Plant & Food Research) for permission to use photographs.
1 December 2018. NA Martin. Changed symbol used for apostrophes.