Horned beech scale - Solenophora fagi

By N A Martin (2019)

Caption:

Classification

Phylum

Arthropoda

Class

Insecta

Order

Hemiptera

Superfamily

Coccoidea

Family

Cerococcidae

Scientific name

Solenophora fagi Maskell, 1890

Common names

Horned beech scale, Beech false pit scale

Synonyms

Solenoccocus fagi (Maskell, 1890),

Cerococcus fagi (Maskell, 1890)

Biostatus and distribution

The distinctive endemic Horned beech scale insects live on twigs and thin branches on Southern beech (Nothofagaceae) trees. They have been found on four of the five New Zealand species. They were first found in the 1880’s by Maskell and given their common name by David Miller in 1922. They live in both the North and South Islands.

Conservation status: Not endangered, probably widespread on its host trees.

Life stages and annual cycle

Lifecycle of a soft scale, Coccidae (Hemiptera). The male propupae and pupa live under the male second instar cover. In this example there are three nymphal stages before the adult female. Creator: Nicholas A. Martin. © Diagram adapted from Figure 2 in Hodgson C.J. and Henderson R.C. 2000. Fauna of New Zealand. 41. [Image: 2MT3]

The Horned beech scale may have more than one generation per year. Maskell’s 1890 drawing of the scale insects on a branch of beech shows young scale insects as well as mature females and male cocoons. I found young and mature females in May. The insects live on twigs and young branches of Southern beech trees.

The cover of the adult female is limpet like when seen from the side. At the top is the moulted skin of the previous nymph. It is dark and rather shiny. The main part of the scale cover is brown with very fine concentric horizontal ridges and 4 white radiating lines. When viewed from the side older females have a short curved ‘spout’ at their hind end. This contains the anus and it is thought to make it easier for the adult male to fertilise the female. After fertilization, the female lays eggs under the scale cover and her body shrinks as it is converted into eggs.

After the first instar nymphs, crawlers, hatch from their eggs, they leave the female scale cover. They are about 0.6 mm long. They have three pairs of legs and a pair of antennae and walk to another young branch or twig on the tree and start to feed. The first instar nymph crawls to where the adult female or adult male will develop. When they have reached full size, they moult into the next nymphal stage. There may be two or three female nymphal stages. The last nymphal stage has no functional legs. After moulting it is covered with a loose yellow cottony secretion. When fully grown it moults into the adult female.

After the second instar male nymph is fully grown, it covers itself with a cylindrical yellowish sac of a closely felted secretion about 1.6 mm long. In side this sac, it moults into a non-feeding propupa that in turn moults into a red pupa, about 1 mm long, that has wing buds. It is presumed that the pupa moults into an adult winged male that also has functional legs. In many other scale insects, the males can mate with females in their own colony, but can also go to females in other colonies.

Feeding

Adult females and the nymphs 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 nymphs have legs and can walk. They are often called crawlers. All the other nymphal stages and adult females have no functional legs. The first instar nymph is the main stage for dispersal. Most crawlers walk to a place on a twig or another branch. Some crawlers disperse to other trees; 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 stem in search of females with which to mate. They can also fly to nearby colonies, and may be carried further by wind.

Two adult female Horned beech scales, Solenophora fagi (Hemiptera: Cerococcidae) on a twig of a Black beech tree, Fuscospora solandri (Nothofagaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 31TL]

Side view of an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae) on a twig of a Black beech tree, Fuscospora solandri (Nothofagaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 31TK]

Top view of an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae) on a twig of a Black beech tree, Fuscospora solandri (Nothofagaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 31TM]

Side view of an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae) on a twig of a Black beech tree, Fuscospora solandri (Nothofagaceae): note the ‘spout’ at its hind end. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 31TP]

Drawings of Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae), including mature females, a male cocoon, and many scale insects on a branch of a beech tree. Creator: Maskell WM. © Drawings from Plate V in Maskell WM. 1890: Further notes on Coccidae with descriptions of new species from Australia, Fiji and New Zealand. Transactions and Proceedings of the New Zealand Institute, 22:133-156. [Image: 31TT]

Photograph of a microscope slide of an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae). Creator: Nicholas A. Martin. © Landcare Research. [Image: 31TS]

Photograph of a microscope slide of the hind end of an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae). Creator: Nicholas A. Martin. © Landcare Research. [Image: 31TR]

Recognition

The young and mature adult female Horned beech scale have a distinctive appearance and are only found on the twigs and thin branches of Southern beech (Nothofagaceae) trees. The young adult female is limpet shaped. It is dark coloured with several white lines running from the edge to the central dark cap. The mature adult female stands higher and viewed from the side has short curved ‘spout’ at its hind end.

The larger Glassy beech scale, Crystallotesta neofagi (Hemiptera: Coccidae) may also be found on the same branches of a tree. Their scale cover is made up of transparent wax plates.

A twig of a Black beech tree, Fuscospora solandri (Nothofagaceae) with on the right an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae) and on the left, an adult female Glassy beech scale, Crystallotesta neofagi (Hemiptera: Coccidae): note the wax plates forming the scale cover. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 31TN]

Natural enemies

No natural enemies of the Horned beech scale are known. They may be eaten by predatory insects and birds.

Host plants

Horned beech scale insects live on twigs and thin branches on Southern beech (Nothofagaceae) trees. They have been found on four of the five species. It remains to be found on red beech, Fuscospora fusca.

Feeding and honeydew

Like other Hemiptera, Horned beech 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 Horned beech 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.

Table: Host plants of the Horned beech scale, *Solenophora fagi* (Hemiptera: Cerococcidae) from Plant-SyNZ database (22 May 2019). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)	Scientific Name	Family	Reliability Index	Biostatus
Mountain beech, Tawhai rauriki	Fuscospora cliffortioides (Hook.f.) Heenan & Smissen	Nothofagaceae	10	endemic
Black beech, Tawhai rauriki	Fuscospora solandri (Hook.f.) Heenan & Smissen	Nothofagaceae	10	endemic
Hard beech, Hutu, Hututawai, Tawhai raunui	Fuscospora truncata (Colenso) Heenan & Smissen	Nothofagaceae	10	endemic
Silver beech, Tawai, Tawhai	Lophozonia menziesii (Hook.f.) Heenan & Smissen	Nothofagaceae	10	endemic

Information sources

Maskell WM. 1890: Further notes on Coccidae with descriptions of new species from Australia, Fiji and New Zealand. Transactions and Proceedings of the New Zealand Institute, 22:133-156.

Miller, D. 1925 Forest and timber insects in New Zealand. Bulletin of the New Zealand State Forest Service (Wellington) 2: 1-76.

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.

Landcare Research New Zealand Limited (Landcare Research) for permission to use photographs.

Other images

Photograph of a microscope slide of an adult female Horned beech scale, Solenophora fagi (Hemiptera: Cerococcidae). Creator: Nicholas A. Martin. © Landcare Research. [Image: 31TQ]

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