INTERESTING INSECTS

By N A Martin (2019)

Toetoe felted scale

This endemic scale insect lives on leaves of native tussock grasses (Gramineae) in the genera Austroderia, Chionochloa and Rytidosperma growing in native habitats. It has been found in three places, Auckland by a West Coast Beach, near Lewis Pass and Nelson mountains in the South Island.

Conservation status: A native species found in native ecosystems on tussock grasses in the North & South Islands.

This distinctive and unusual felted scale has a naked adult female, that is it is not enclosed in a sac. The Toetoe felted scale, which lives on leaves of tussock grasses, appears to breed all year in Auckland, but probably has a main summer generation in colder areas. In this recent study, male pupae and adults have not been found.

The adult female is about 4 mm long and 1.5 mm wide. The body is surrounded by setae (hairs) that are longest at both ends of the body. There is an indentation at the end of the body where white wax from the anal aperture may be seen. The abdominal segmentation is visible. There are three pairs of legs on the underside of the body. A short pair of antennae projects forward near the centre line. There is a long fine seta at its apex. On the underside of the head a short rostrum that holds the stylets used for feeding. The female appears to give birth to live nymph. The areas where this happens are marked by white wax on the surface of the grass leaf.

The nymphs look like small adult females. They have the same shape and surrounding setae, legs, antennae and rostrum with stylets for feeding. They also tend to align themselves with the grooves of the grass leaves. They young nymphs may stay on the same leaf as the adult female or crawl to younger leaves. When a nymph is fully grown grown it moults, their skin splits allowing the insect to grow a new and larger skin. There are three female nymphal stages and two male nymphal stages.

It is presumed that the males are like those of other species of Eriococcus. The fully grown male second instar nymph passes through two legless, non-feeding stages, a prepupa and a pupa. Other species form a sac in which these stages live. The moulted skins are pushed out the open rear end of the sac. The adult male has a pair of wings and while the body is hardening in the sac, it grows a pair of long white wax tails that help balance the male during flight. It walks over leaves looking for females with which to mate. It may also fly to other plants. The adult male does not feed.

Feeding

Adult females and nymphs of Toetoe felted 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 nymphs and adult females and it is assumed the adult males have legs and can walk. The first instar, which is commonly called a crawler, is the main stage for dispersal. Most crawlers walk to a place on a plant leaf where they settle to feed. Some crawlers disperse to other leaves. Some 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 of Felted scale insects 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 nearby colonies, and may be carried further by wind.

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HI]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HN]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the pale forward pointing antennae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HM]

Underside of an adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HT]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the white wax at the hind end of the female that iindicating that she has been feeding for a while at this site Creator: Tim Holmes. © Plant & Food Research. [Image: 30HD]

Nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Tim Holmes. © Plant & Food Research. [Image: 30HF]

Two nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the dark nymph (right) that may have just moulted, has forward pointing antennae. Creator: Tim Holmes. © Plant & Food Research. [Image: 30HE]

An adult female and nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the white wax and moulted nymphal skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HL]

Nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a juvenile leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Tim Holmes. © Plant & Food Research. [Image: 30HC]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the white wax on the leaf and liquid on the rear of the body. Creator: Tim Holmes. © Plant & Food Research. [Image: 30HG]

Felted scale insects (Eriococcidae) require specialist skills for their identification. However, on its known host plants, Toetoe felted scale appear to be sufficiently distinct to theirenable identification. The host plants species are in three genera of grasses (Gramineae), Austroderia, Chionochloa and Rytidosperma. Adult female Toetoe felted scale are ‘naked’, that is they are not covered by sac. Whereas, the adult females Eriococcus nitidulus has a waxen, shinning and tawny coloured sac. The adult female of the one Montanococcus species for which there is a description of live insects lives under the leaf blade at its base. Also it has a very long white wax tube coming from its anus.

The distinctive features of the Toetoe felted scale are the naked adult female, the elongated shape of females and juvenile males and the setae (hairs) all around their body. These setae are longer at the front and back.

Leaves of Toetoe, Austroderia splendens, may also bear narrow, white Cordyline scale, Anzaspis cordylinidis (Diaspididae) which are very different.

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HI]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HN]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Tim Holmes. © Plant & Food Research. [Image: 30HH]

Nymph of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the white wax showing where an adult female had been feeding. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HJ]

Nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HQ]

Large number of nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a young leaf of Toetoe, Austroderia splendens (Gramineae). Such high numbers are very rarely seen. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HA]

Two Cordyline scale, Anzaspis cordylinidis (Diaspididae) on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30H9]

Cordyline scale, Anzaspis cordylinidis (Diaspididae) on a leaf of Toetoe, Austroderia splendens (Gramineae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30H8]

No pathogens or predators of this scale insect have been reported.

Parasitoids

The only known natural enemy is an endemic parasitic wasp (Hymenoptera) that has been reared from unnamed scale insects on a host plant of Toetoe felted scale. It has also been reared from a felted scale insect on another species of grass.

Toetoe felted scale insects have been found on the leaves of three grasses (Gramineae). On Toetoe, Austroderia splendens, they have been found on both young expanding leaves and old mature leaves. Numbers on a plant vary greatly. Unlike most Felted scale insects (Eriococcidae) the mature female remains naked. Males cocoons and adults have not yet been seen on this plant.

Feeding and honeydew

Like other Hemiptera, Toetoe felted 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 Toetoe felted 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.

Flowering plants of Toetoe, Austroderia splendens, (Gramineae) a host of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 30HS]

Adult female Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens, (Gramineae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 30HR]

Large number of nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a young leaf of Toetoe, Austroderia splendens (Gramineae). Such high numbers are very rarely seen. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HA]

An adult female and nymphs of Toetoe felted scale, Eriococcus danthoniae (Hemiptera: Eriococcidae), on a leaf of Toetoe, Austroderia splendens (Gramineae): note the white wax and moulted nymphal skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 30HL]

Henderson RC. 2007. Three new genera and six new species of felt scales (Hemiptera: Coccoidea: Eriococcidae) from Mountain Habitats in New Zealand. Zootaxa. 1449: 1-29.

Hoy JM. 1962. Eriococcidae (Homoptera: Coccoidea) of New Zealand. New Zealand Department of Scientific and Industrial Research Bulletin. 146: 1-219.

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.

Juliette Richmond (Ministry for Primary Industries, Auckland) for the identification of Eriococcus danthoniae found on Toetoe, Austroderia splendens.