Peppercorn scale - Epelidochiton piperis
By N A Martin (2017 revised 2018)
Classification
Insecta
Hemiptera
Coccoidea
Coccidae
Epelidochiton piperis (Maskell, 1882)
Common names
Peppercorn scale
Synonyms
Ctenochiton piperis Maskell 1882
Biostatus and distribution
This distinctive endemic scale insect is found on the underside of leaves of its tree and shrub host plants. It lives in lowland forests and on urban trees in northern North Island and northern South Island.
Conservation status: Not endangered, often abundant even on urban trees in Auckland.
Life stages and annual cycle
Peppercorn scale insects have several overlapping generations per year in Auckland. The life history in the South Island is not known. Unlike most other adult female New Zealand Coccidae, adult female Peppercorn scale insects are not entirely sessile and can walk off the underside of the leaves (their preferred feeding site) when disturbed. It is thought that this is an adaptation for moving to new feeding sites, particularly after overwintering on older leaves.
The bodies of adult females and female and male nymphs are covered by a test, glassy wax plates, secreted by the upper surface of the insect’s body. On the underside of the body are three pairs of legs and a pair of antennae. There is also a short rostrum which houses the stylets that are used for feeding. When a nymph is fully grown it moults, shedding its old skin, but it stays beneath its test. It may walk to a new site where it settles down to feed, grow and enlarge the test.
The first instar nymphs of males and females are identical. The first instar nymphs, often called crawlers, are the main dispersal stage of Peppercorn scale. When it is fully grown, it moults, changes its skin, but keeping the test. The second instar nymph is also a feeding stage. The males and females can be distinguished. The male nymphs develop a more elongate, glassy test. When the male has finished feeding it may move to a new site where it secretes a wax base that firmly attaches it to the plant surface. Under the test the male nymph moults into a propupa, a non-feeding stage with short wing buds. Later the propupa moults into a pupa which has larger wing buds. When the adult male has fully formed, the pupal skin is shed. It has one pair of wings and emerges backwards from beneath the test, wingtips first, by means of the upwardly flexing plate on the posterior end of the test. It is a non-feeding stage and only lives for a few days while it finds and mates with a female.
Females have three nymphal instars (stages). They all feed and the only difference between them is size. The young adult female is the size of the fully grown third instar nymph and grows to about 2-3 times that size. The young adult is rather flat and round with a glossy test of wax plates. It becomes more convex when mature. The body of the young female is light green but gradually becomes dark grey. It can be seen through the glassy wax plates. Each wax plate is convex, composed of layers of wax, uppermost layers at centre of each plate is the smallest and narrowest (secreted when insect was small); most basal layers of each plate are the broadest, filling plate area (and secreted most recently). The mature female has a central brood chamber into which eggs are laid and in which the nymphs hatch before leaving.
Feeding
Adult females and juvenile scales 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 nymphs and adult females retain legs and can walk, though the adult female and the second and third instar (stage) nymphs are much less likely to walk than the first instar which is commonly called a crawler. It is the main stage for dispersal. Most crawlers walk to a place on the leaf or another leaf on the stem or branch. Some crawlers disperse to other plants; 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. Adult males have legs and wings. They can walk over a leaf in search of females with which to mate. They can also fly to nearby colonies, and may be carried further by wind.
Recognition
The mature female Peppercorn scale are distinctive; almost circular, convex and darkly pigmented. In slightly younger females the dark pigment is only in the centre of each wax plate.
Male scales are similar in appearance to those of other species of soft scale insects (Coccidae) and are found in colonies with females. Younger female scales are not as round, flatter and shiny.
Natural enemies
Three kinds of natural enemy have been found associated with Peppercorn scale insects, fungal pathogens, two wasp parasitoids and predators.
Pathogens
At least three fungal pathogens have been seen on Peppercorn scale insects. The brown fungus, Tompetchia webberi may infect and kill all or most of the scale insects on the underside of a leaf. It is associated with Coccidae. Two white fungi have been found infesting Peppercorn scale insects. They are awaiting identifiaction.
Parasitoids
At least two species of wasp parasitoids have been reared from Peppercorn scale insects. The only named wasp parasitoid, Aphobetus nanai (Pteromalidae) has mainly been reared from Coocidae.
The female parasitoids lay an egg in a scale insect. The larva lives in or on the body of the scale insect. When the with wasp larva is fully grown it kills the scale insect and pupates under the scale cover. The adult wasp chews a hole in the scale cover though which it emerged.
Predators
Larvae of an unknown lacewing and three ladybirds have been found associated with Peppercorn scale insects. The lacewing and one of the ladybirds, Serangium maculigerum, were probably feeding on the first instar (stage) nymphs of the scale insect. The other ladybirds may also feed on larger scale insects.
Scientific Name | Common Name | Classification | Enemy Type | Reliability Index | Biostatus |
---|---|---|---|---|---|
Aphobetus nana (Boucek, 1988) | (Wasp) | Hymenoptera: Pteromalidae | parasitoid | 10 | endemic |
Tompetchia webberi (H.S. Fawc.) Subram. | Ascomycota | pathogen | 9 | indigenous, non-endemic | |
Halmus chalybeus (Boisduval, 1835) | Steelblue ladybird (Beetle) | Coleoptera: Coccinellidae | predator | 10 | adventive |
Neuroptera sp. | Lacewing (Lacewing) | Neuroptera: | predator | 5 | unknown |
Rhyzobius sp. | (Beetle) | Coleoptera: Coccinellidae | predator | 7 | unknown |
Serangium maculigerum Blackburn, 1892 | Citrus whitefly ladybird (Beetle) | Coleoptera: Coccinellidae | predator | 10 | adventive |
Host plants
Peppercorn scale insects are found on the underside of leaves of trees and shrubs. Some species of tree regularly have many scale insects on their leaves while other have only ever have a few. All known hat plants are indigenous to New Zealand except Lawson's cypress, Chamaecyparis lawsoniana (Cupressaceae). The infested Lawson’s cyrpus tree was growing under old native trees which were the likely source of the scale insects.
Feeding and honeydew
Like other Hemiptera, Peppercorn 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 Peppercorn scale 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.
Common Name(s) | Scientific Name | Family | Reliability Index | Biostatus |
---|---|---|---|---|
New Zealand ash, Tapitapi, Tītoki, Tītongi, Tokitoki, Tongitongi, Topitopi | Alectryon excelsus Gaertn. | Sapindaceae | 10 | endemic |
Wineberry, Mako, Makomako | Aristotelia serrata (J.R.Forst. & G.Forst.) W.R.B.Oliver | Elaeocarpaceae | 10 | endemic |
Tawa, Tawa rautangi | Beilschmiedia tawa (A.Cunn.) Benth. & Hook.f. ex Kirk | Lauraceae | 10 | endemic |
Lawson's cypress, Port Oreford cedar, lawson cypress, Lawsoniana | Chamaecyparis lawsoniana (A.Murray) Parl. | Cupressaceae | 10 | naturalised |
Mexican orange blossom | Choisya ternata Kunth | Rutaceae | 10 | cultivated |
Coprosma acutifolia Hook.f. | Rubiaceae | 10 | endemic | |
Large seeded coprosma, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū | Coprosma macrocarpa Cheeseman | Rubiaceae | 10 | endemic |
Glossy karamu, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū | Coprosma robusta Raoul | Rubiaceae | 10 | endemic |
Karaka nut, Karaka, Kōpī | Corynocarpus laevigatus J.R.Forst. & G.Forst. | Corynocarpaceae | 10 | endemic |
New Zealand mahogany, Kohe, Kohekohe, Koheriki, Kohepi (flowers), Kohepu (flowers), Māota (flowers) | Dysoxylum spectabile (G.Forst.) Hook.f. | Meliaceae | 10 | endemic |
Pigeonwood, Kaiwhir, Kaiwhiria, Kōporokaiwhiri, Pōporokaiwhiri, Pōporokaiwhiria, Porokaiwhiri, Porokaiwhiria, Poroporokaiwhiria | Hedycarya arborea J.R.Forst. & G.Forst. | Monimiaceae | 10 | endemic |
Lacebark, Hohere, Hoihere, Houhere, Houhi, Houhi ongaonga, Houī, Ongaonga, Whauahi, Wheuhi | Hoheria populnea A.Cunn | Malvaceae | 10 | endemic |
Norfolk island hibiscus, Pyramid tree, Whitewood | Lagunaria pattersonii (Andrews) G.Don | Malvaceae | 10 | naturalised |
Pukatea, Puketea | Laurelia novae-zelandiae A. Cunn. | Atherospermataceae | 10 | endemic |
Māhoe | Melicytus sp. | Violaceae | 7 | unknown |
Aka, Rātā | Metrosideros sp. | Myrtaceae | 7 | unknown |
Pepper tree, Kawa, Kawakawa | Piper excelsum G.Forst. | Piperaceae | 10 | endemic |
Lemonwood, Kīhihi, Tarata | Pittosporum eugenioides A.Cunn. | Pittosporaceae | 10 | endemic |
Seven-finger, Kohi, Kotētē, Patate, Patatē, Patē, Patētē | Schefflera digitata J.R.Forst. & G.Forst. | Araliaceae | 10 | endemic |
New Zealand oak, Kauere, Pūriri | Vitex lucens Kirk | Labiatae | 10 | endemic |
Honeydew feeding
Peppercorn scale insects have sucking mouth parts. The stylets are inserted 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. Honeydew lands on leaves and plants below. When a lot of honeydew is excreted, black sooty mould fungi grow on the sticky leaves.
Some insects such as bees and wasps feed on honeydew, but none have been recorded feeding on Peppercorn scale honeydew.
Information sources
Hodgson CJ, Henderson RC. 2000. Coccidae (Insecta: Hemiptera: Coccoidea). Fauna of New Zealand. 41: 1-264.
Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/
Acknowledgements
The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.
Other images
Update history
1 August 2018, NA Martin. Photos on 2 host plants added.