INTERESTING INSECTS

By N A Martin (2015)

Ngaio mirid

This endemic mirid is found throughout New Zealand on its host plant, ngaio, Myoporum laetum (Myporaceae). Both the nymphs and adults feed on young leaves and stems. The mirid occurs in city gardens and parks as well as native ecosystems.

Conservation status: Widespread, not threatened.

In Auckland, adults and nymphs can be found at all times of the year, where there may be three or more overlapping generations. There are likely to be fewer generations in cooler parts of the country.

Adults are found on shoots with young leaves. They often hide on the other side of a leaf or stem. They are mottled brown. The female has an ovipositor, at the tip of her abdomen that is used to insert eggs into leaves or young stems.

Nymphs hatch from the eggs. There are five nymphal stages, each is called an instar. Nymphs go from one stage to the next by moulting (changing their skin). During moulting, the skin on the dorsal side splits and the next stage pulls itself out of the old skin. First instar nymphs are like small, green, wingless adults. As the insects progress through the nymphal stages, the colour remains predominately green. The third instar has small wing buds and only those of the forewing are visible. In the fourth and fifth instars both pairs of wing buds are visible and tend to be darker green in colour. They are largest in the 5th instar. Adults emerge from fifth instar nymphs.

Walking and flying

Nymphs and adults have three pairs of legs. Adults have two pairs of wings, the front chitinised pair covering the membranous hind wings when not flying. Most of the forewing is opaque mottled brown, the rest is membranous.

Feeding

Like other Hemiptera, the ngaio mirid has piercing and sucking mouth parts. The long stylets, special shaped rods, are held in the rostrum. When it wishes to feed the bug moves the tip of the rostrum to a suitable part of the plant. The stylets are then gradually pushed into the plant. The stylets form two tubes, one through which saliva is injected into the plant and a second through which plant juices are sucked up into the insect. Ngaio mirid feeding has not been studied, but the damage to leaves show that they feed on the cells in the leaf and from one point of insertion of the stylets, can reach in all directions forming a ‘star-like’ pattern of pale, damaged tissue. They probably use their saliva to digest the plant cells.

Adult ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae) on leaf of host plant, ngaio, Myoporum laetum (Myoporaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 1582]

Underside of an adult ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157U]

Front of an adult ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Tim Holmes. © Plant & Food Research. [Image: 1581]

Side view of a female adult ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157Z]

A ngaio mirid nymph, Chinamiris aurantiacus (Hemiptera: Miridae), probably a first or second instar (stage) from above. Creator: Tim Holmes. © Plant & Food Research. [Image: 157Q]

A ngaio mirid nymph, Chinamiris aurantiacus (Hemiptera: Miridae), probably a first or second instar (stage) from above. Creator: Tim Holmes. © Plant & Food Research. [Image: 157S]

A ngaio mirid fourth instar (stage) nymph, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157R]

A ngaio mirid third or fourth instar nymph from above, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157X]

A fifth instar ngaio mirid nymph, Chinamiris aurantiacus (Hemiptera: Miridae); note the large dark coloured wing pads. Creator: Tim Holmes. © Plant & Food Research. [Image: 157V]

Side, slightly dorsal view of a fifth instar ngaio mirid nymph, Chinamiris aurantiacus (Hemiptera: Miridae), note the large dark coloured wing pads. Creator: Tim Holmes. © Plant & Food Research. [Image: 157W]

Side, slightly ventral view of a fifth instar ngaio mirid nymph, Chinamiris aurantiacus (Hemiptera: Miridae), note the rostrum extending from the head back between the legs. Creator: Tim Holmes. © Plant & Food Research. [Image: 157Y]

Moulted nymphal skin of a ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae), attached to the underside of a leaf of ngaio, Myoporum laetum (Myoporaceae) Creator: Tim Holmes. © Plant & Food Research. [Image: 157M]

Moulted nymphal skin of a ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae), attached to the underside of a ngaio leaf, Myoporum laetum (Myoporaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157N]

Upper side of leaf of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) caused by ngaio mirids, Chinamiris aurantiacus. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1583]

Underside of leaf of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) caused by, and black faecal deposits of,ngaio mirids, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1584]

Upper side of leaf of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) caused by ngaio mirids, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1589]

Underside of leaf of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) caused by, and black faecal deposits of, ngaio mirids, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1588]

The ngaio mirid is the only mirid that breeds on ngaio, Myoporum laetum (Myoporaceae). However, another hemipteran, the Yellow Australasian leafhopper, Anzygina zealandica (Hemiptera: Cicadellidae), also causes yellowing of ngaio leaves. The two insects and their damage can be distinguished by the following.

The adult ngaio mirid is mottled brown, whereas the adult Yellow Australasian leafhopper is smaller, narrower, and yellow-green. The nymphs of both species are green. Nymphs of the ngaio mirid are agile and often run to the other side of a stem or leaf when disturbed. The Yellow Australasian leafhopper nymphs are more slender and, like the adults, tend to move sideways. The ngaio mirid is the only mirid that breeds on ngaio, Myoporum laetum (Myoporaceae). Feeding by both the mirid and the leafhopper insects causes yellow areas on the leaves, but only the ngaio mirid makes black faecal deposits on the underside of the leaves.

Adult ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae) on leaf of host plant, ngaio, Myoporum laetum (Myoporaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 1582]

Fifth instar (stage) nymph ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae) on leaf of host plant, ngaio, Myoporum laetum (Myoporaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157T]

A ngaio mirid fourth instar (stage) nymph, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157R]

Moulted nymphal skin of a ngaio mirid, Chinamiris aurantiacus (Hemiptera: Miridae), attached to the underside of a ngaio leaf, Myoporum laetum (Myoporaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157N]

Underside (left) and upper side of leaves of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) and black faecal deposits (on the underside of the leaf) caused by ngaio mirids, Chinamiris aurantiacus (Hemiptera: Miridae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1587]

Underside (left) and upper side of leaves of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas, not the chewed leaf edge) caused by the Yellow Australasian leafhopper, Anzygina zealandica (Hemiptera: Cicadellidae); note the absence of black faecal deposits. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 157K]

Moulted nymphal skins and a nymph of the Yellow Australasian leafhopper, Anzygina zealandica (Hemiptera: Cicadellidae), on the underside of a ngaio leaf,Myoporum laetum (Myoporaceae), note the narrow shape of the nymph and the skins. Creator: Tim Holmes. © Plant & Food Research. [Image: 157J]

Moulted nymphal skins of the Yellow Australasian leafhopper, Anzygina zealandica (Hemiptera: Cicadellidae), on the underside of a ngaio leaf Myoporum laetum (Myoporaceae), note the narrow shape of the skins, Creator: Tim Holmes. © Plant & Food Research. [Image: 157I]

Adult and nymph of the Yellow Australasian leafhopper, Anzygina zealandica (Hemiptera: Cicadellidae), on the underside of a ngaio leaf Myoporum laetum (Myoporaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 157L]

No natural enemies of the ngaio mirid are known. They may be caught by birds, spiders and predatory insects.

The ngaio mirid lives and breeds on the New Zealand endemic tree, ngaio, Myoporum laetum Forst. f. (Myoporaceae). The species has been found feeding on hybrids between ngaio and the Australian species, Myoporum insulare R.Br., but does not appear to feed and breed on the Australian species. Adults and juveniles feed by inserting the stylets into plant leaves and perhaps young stems. It is assumed that they inject saliva into plant cells and suck up predigested or partly digested cell contents from the leaves.

Side view of a fifth instar (stage) ngaio mirid nymph, Chinamiris aurantiacus (Hemiptera: Miridae); note the rostrum extending from the head back between the legs. Creator: Tim Holmes. © Plant & Food Research. [Image: 157P]

Upper side of leaf of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) caused by ngaio mirids Chinamiris aurantiacus (Hemiptera: Miridae) to the upper side of a ngaio leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1585]

Underside of leaf of ngaio, Myoporum laetum (Myoporaceae) showing feeding damage (pale areas) caused by, and black faecal deposits of ngaio mirids, Chinamiris aurantiacus (Hemiptera: Miridae) on the underside of a ngaio leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 1586]

Normally, mirid damage to ngaio trees does not cause trees any significant harm. However, extensive damage to leaves of ngaio trees can occur. Nothing is known about its natural control. If there is concern about the damage to a young tree, application of a non-persistent insecticide to all the leaves on the tree may help.

Damage to other plants by Chinamiris mirids

Several different species of Chinamiris mirids live on native ornamental shrubs in gardens and plant nurseries. Sometimes they cause obvious damage to these plants.

Mirid opportunists

Mirids are opportunists (Wheeler 2001) and it is possible that this mirid will prey on aphids and other small insects on its host plant..

Eyles AC, Carvalho JCM 1991. Revision of the genus Chinamiris Woodward (Hemiptera: Miridae). New Zealand Journal of Zoology 18: 267-321.

Lariviere M-C, Larochelle A 2004. Heteropter(Insecta: Hemiptera): catalogue. Fauna of New Zealand 50: 1-326.

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.

Wheeler AG 2001. Biology of the plant bugs (Hemiptera: Miridae): pests, predators, opportunists. New York, Cornell University Press. 506 p.

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