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Kanuka giant scale - Coelostomidia wairoensis

By N A Martin (2018)

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Click to collapse Classification Info






Coelostomidia wairoensis (Maskell, 1884)

Click to collapse Synonyms Info

Caelostoma wairoensis Maskell, 1884

Coelostoma wairoensis Maskell, 1887

Click to collapse Taxonomic notes Info

Since Clare Morales revision of New Zealand Margarodidae in 1991, there has been a revision of the family classification of the genera found in New Zealand. In fact, recent publications by Chris Hodgson and others, show that there are likely to be more changes to the Family classification of the Coccoidea, the superfamily that includes all scale insects. The change that concerns this factsheet is that the genus Coelostomidia is now placed in the family Coelostomidiidae which also contains another native genus, Ulracoelostoma.

Click to collapse Biostatus and distribution Info

This endemic scale insect lives on stems of native several trees and shrubs. It is particularly common Kanuka, Kunzea species (Myrtaceae). It is present in native habitats and in parks. It is present in the North and South Islands.

Conservation status: A native species found mainly in native ecosystems on native trees and shrubs in the North & South Islands.

Click to collapse Life stages and annual cycle Info

The Kanuka giant scale has a distinct annual cycle. It overwinters as mated adult females. In the spring they lay eggs in their test (scale cover). In late spring the eggs hatch and the mobile first instar (stage) nymphs leave the female test and settle on a plant stem to feed. The second instar in non-mobile. In February the next male stage is a mobile non-feeding prepupa that moves from the feeding stems. They often gather in large numbers on the tree trunk or branches and form white cocoons in which they pupate. In May, the adult males emerge and search out and mate with the adult females. The females have a third non-mobile nymphal stage.

The adult females are found on stems of host plants. They are surrounded by a wax test (scale cover). It is brown and may be blackened by sooty moulds. At the anal end white wax may protrude. If the adult female has stayed in the test of the nymph, the remains of the wax tube used for excreting honeydew may still be present. Many of the following details come from Clare Morales 1991 paper on the Margarodidae. The adult female is about 6 mm long and 3 mm wide. It has eyes, a pair of antennae and three pairs of legs and is able to walk to a new site on which to form its test. Adult females of other New Zealand species of Coelostomidia walk to new egg laying sites, but the Kanuka giant scale appears to do so infrequently. When the female is ready to lay eggs it turns round in its test so that its head is by the exit for the anal filament. It lays up to 110 eggs. The female may die in the test, the shrivelled body partly blocking the exit. The eggs almost 1 mm long, bright pink and dusted with white wax. The crawlers, first instar, nymphs hatch in the test and leave through the anal filament aperture.

The first instar nymphs are about 0.8 mm long, bright pink, have well developed antennae and three pairs of legs. They walk to a place to settle and feed, usually a crevice in a previous seasons shoot or less often a new seasons shoot. They become covered in white fluffy wax which later becomes a pale brown, rather papery test. They also develop a long wax tube through which they excrete the sugary waste, honeydew. When fully grown the first instar nymph moults into the second instar. This differs from the first instar nymph, by having reduced, non-functional antennae and legs. The test expands to accommodate the larger insect. The female third instar nymph is similar, but larger. All the nymphal instars can feed. On the underside of the head is a rostrum that contains the stylets used for feeding. When the third instar nymph has reached full size, it moults into the non-feeding, but mobile adult female. Mating occurs while the female is in the nymphal test, with the female’s abdomen protruding from the test during mating.

The male has only two feeding stages, the first and second instar nymphs that are identical to those of the female. When the male second instar nymph is fully grown, it moults into the non-feeding prepupa. They push themselves out of the anal filament aperture and rupture the side of the test. They are 4 mm long and brick red. They have fully developed antennae and three pairs of legs and very small wing buds. Between February and April, they can be seen crawling on trunks and branches of host plant trees and adjacent trees and shrubs. They settle in large numbers on trunks and branches, where they make white cocoons about 5 mm long in which they pupate. The prepupa takes about a month to pupate, and spends another month as a pupa. The immobile pupa has large wing buds and is also brick red. The adult male has one pair of well-developed wings, antennae, legs and compound eyes. The body is dark pinkish purple with clear purplish wings. They search for females with whom to mate. Mating occurs in May and June. The male may fly to other trees in its search for scale colonies.


Nymphs of Kanuka giant scale have sucking mouthparts. Specially shaped long rods called stylets are used for feeding. Until used for feeding the tips of the stylets held in the short sheath-like rostrum. When it wishes to feed, the scale insect moves the tip of the rostrum onto the surface of the plant. The stylets are then gradually pushed into the plant. The stylets form two tubes, one down which saliva is pumped into plant cells and the second tube through which it sucks the contents of the plant cells. The insect inserts its stylets into the phloem, the plant vessels for transmitting sap from the leaves to other parts of the plant. The sap has a high volume of water and sugars, more than the insect needs. It excretes the excess water and sugar, which is called honeydew.

Walking, flying and dispersal

The first instar nymph (crawler), the male prepupa and adult males and females have legs large enough for walking. The first instar, which is commonly called a crawler, is the main stage for dispersal. Most crawlers walk to a place on the plant stem on which they are born and settle there to feed. Some crawlers disperse to other stems and branches. Some to other trees or shrubs; most long distance dispersal is by air. It is not known if crawlers of this species go to high points of the plant and stand up to catch the wind. Fully grown females walk from their feeding site to another part of the stem, but may not always do so. The male prepupa walks from the feeding stems to another part of the tree or even a nearby tree on which to make its cocoon for the pupa. Adult males have wings as well as legs. They can walk over leaves and stems in search of females with which to mate. They can also fly to other parts of the tree or nearby colonies, and may be carried further by wind.

Click to collapse Recognition Info

Giant scale insects (Coelostomidiidae) require specialist skills for their identification. The Kanuka giant scale is the only species of the family known on seven of the nine known host plants. On these plants, Kunzea species, Metrosideros species, Olearia furfuracea, Ozothamnus leptophyllus and Pinus radiata, this scale insect can readily be recognised the presence of long wax tubes for excreting honeydew and when populations are high, by the presence of male cocoons on the trunks of the trees. The presence of much black sooty mould is an indication that the Kanuka giant scale is present, but other scale insects also secrete honeydew and induce sooty moulds.

Click to collapse Natural enemies Info

No Pathogens or parasitoids of the Kanuka giant scale are known.


Three predators have been reported. One is a caterpillar that feeds on the eggs and young scales. The larvae of a fly also feed on the scale eggs. A parakeet has been observed breaking open the tests (scale covers) and feeding on the contents.

Table: Predators of Kanuka giant scale, Coelostomidia wairoensis (Hemiptera: Coelostomidiidae), from Plant-SyNZ database (25 February 2018). The reliability index shows the quality of evidence for the host association (0-10, 10=high quality).
Scientific NameCommon NameClassificationEnemy TypeReliability IndexBiostatus
Cecidomyiidae sp. 'predators' (Fly)Diptera: Cecidomyiidaepredator5unknown
Cyanoramphus auriceps (Kuhl, 1820)Yellow-crowned parakeet (Bird)Psittaciformes: Psittaculidaeomnivore9endemic
Stathmopoda coracodes Meyrick, 1923 (Moth or Butterfly)Lepidoptera: Stathmopodidaepredator10endemic

Click to collapse Host plants Info

Kanuka giant scale is found mainly on native plants in the families, Myrtaceae, Compositae and Podocarpaceae. It has been found on once on an adventive species, Pinus radiata.

It is often abundant on Kanuka, Kunzea species. Plants in the genus have recently been revised and it is not now known which of the newly described species are hosts of the Kanuka giant scale.

Feeding and honeydew

Like other Hemiptera, the nymphs of Kanuka giant scale insects have sucking mouth parts. The long stylets, special shaped rods, are held in a short rostrum on the underside of the body. When the insect wishes to feed the stylets are then gradually pushed into the plant. The inner pair of stylets, form two tubes, one through which saliva is injected into the plant and a second through which plants juices are sucked up into the insect. The Kanuka giant scale nymph inserts its stylets into the phloem, the plant vessels for transmitting sap from the leaves to other parts of the plant. The sap has a high volume of water and sugars, more than the insect needs. It excretes the excess water and sugar, which is called honeydew. Sooty moulds may grow on the honeydew.

Table: Host plants of the Kanuka giant scale, Coelostomidia wairoensis (Hemiptera: Coelostomidiidae) from Plant-SyNZ database (25 February 2018). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)Scientific NameFamilyReliability IndexBiostatus
Red pine, Amoko, Puaka, RimuDacrydium cupressinum Sol. ex G.Forst.Podocarpaceae10endemic
White tea tree, Kānuka, Kōpuka, Manuea, Mānuka, Mānuka-rauriki, Mārū, Rauiri, RauwiriKunzea ericoides s.l. (A.Rich.) Joy Thomps.Myrtaceae9indigenous, non-endemic
Red tea tree, Tea tree, Kahikātoa, Kātoa, Mānuka, Pata, Rauiri, RauwiriLeptospermum scoparium J.R.Forst. & G.Forst.Myrtaceae10indigenous, non-endemic
New Zealand Christmas tree, Hutukawa, Kahika, Pohutukawa, Pōhutukawa, RātāMetrosideros excelsa Sol. ex Gaertn.Myrtaceae10endemic
Scarlet rata, Vine rata, Aka, Akakura, akatawhitawhi, Akatawhiwhi, Amaru, Kahika, Kāhikahika, Rātā, RātāpikiMetrosideros fulgens Sol. ex Gaertn.Myrtaceae10endemic
Akepiro, Kūmara-kai-torouka, Tanguru, Wharangi-piroOlearia furfuracea (A.Rich.) Hook.f.Compositae9endemic
Cottonwood, TauhinuOzothamnus leptophyllus (G.Forst.) Breitw. & J.M.WardCompositae9endemic
Monterey pine, Radiata pinePinus radiata D. DonPinaceae10naturalised
Brown pine, Miro, ToromiroPrumnopitys ferruginea (D.Don) de Laub.Podocarpaceae10endemic

Click to collapse Honeydew feeding Info

The Kanuka giant scale produces a lot of honeydew which is excreted through a long wax tube. Two species of wasps, Vespula species (Hymenoptera: Vespidae) have been recorded feeding on honeydew. Ants are also associated with the honeydew and I also believe honey bees are. It might be one source of Manuka honey.

It has been suggested that nectar feeding birds may also feed on the scale insect honeydew.

Click to collapse Information sources Info

Gardener-Gee R, Beggs JR. 2009. Distribution and abundance of endemic coelostomidiid scale insects (Hemiptera: Coelostomidiidae) in Auckland forests, New Zealand. New Zealand Journal of Ecology. 33 (2): 138-146.

Hodgson C, Foldi I. 2006. A review of the Margarodidae sensu Morrison (Hemiptera: Coccoidea) and some related taxa based on the morphology of adult males. Zootaxa 1263: 1-250.

Hodgson CJ, Hardy NB. 2013. The phylogeny of the superfamily Coccoidea (Hemiptera: Sternorrhyncha) based on the morphology of extant and extinct macropterous males. Systematic Entomology 38: 794-804.

Morales CF. 1991. Margarodidae (Insecta: Hemiptera). Fauna of New Zealand. 21: 1-123.

Plant-SyNZ: Invertebrate herbivore-host plant association database.

Click to collapse Acknowledgements Info

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

Click to collapse Other images Info

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