INTERESTING INSECTS

By N A Martin (2018)

Serene Scale

Fiorinia minima Maskell, 1884

Fiorinia (Trullifiorinia) minima Maskell, 1884

Trullifiorinia minima (Maskell, 1884)

Chionaspis dysoxyli Maskell, 1885

Pinnaspis dysoxyli (Maskell, 1885)

Chionaspis minori Maskell, 1885

This endemic scale insect lives on leaves and stems of its mainly native host plants. It is most commonly found on Melicytus species (Violaceae) such as Mahoe, Melicytus ramiflorus. It is mainly found in native ecosystems in the North and South Islands.

Conservation status: Widespread in the North and South Island on its host plants and mainly in native ecosystems.

Lifecycle of Diaspidine scale (Hemiptera: Diaspididae: Diaspidinae) with a wingless male. The male prepupae and pupa live under the male second instar cover which has three longitudinal ridges. Creator: Nicholas A. Martin. © Diagram adapted from Figures 1 and 2 in Henderson R.C. 2011. Diaspididae (Insecta: Hemiptera: Coccoidea). Fauna of New Zealand 66. [Image: 2PLP]

Serene scales live on plant leaves and stems and appear to breed all year. Leaves and stems are colonised by mobile first instar (stage) nymphs that are called crawlers. When the crawlers find a suitable place they insert their stylets into the plant to feed. This is where the insect spends most of its life. The male and female first instars appear identical, covered by an oval pale brown cover. The crawler has three pairs of legs and a pair of antennae. The second instar nymphs have no legs and only minute antennae. The the first instar nymph is fully grown it moults, their skin splits allowing the insect to grow a new and larger skin. The second instar nymphs retain the old exuvia (skin) over the front of their body and grow a larger scale cover. This is different in the female and male Serene scale insects.

The second instar female scale becomes tear-drop shaped. When fully grown it moults and retain the exuvia of the earlier stages as part of its covering. The adult female forms a larger tear-drop shape. The scale cover is usually transparent enabling the yellow body to be seen. Some females have a more opaque cover over a pinkish body. The edge of the scale cover is sealed against the plant surface except at the posterior end. That flap allows access for the male genitalia and for the crawlers to escape. When full grown and after mating the female lays yellow eggs under scale cover.

The second instar male forms a very different scale cover. It is made of white felted wax, and is long and narrow, with three ridges. When fully grown the second instar male moults into a prepupa, a non-feeding stage. This later moults into a pupa. The skins of the nymph, prepupa and pupa are ejected through an opening at the rear end of the scale cover. The Serene scale adult male is wingless, but has three pairs of legs, a pair of antennae and a long pointed tip to the abdomen. The wingless adult male is reddish in colour. When its body has hardened it backs out of the scale cover and walks over the leaves and stems of the plant seeking females with which to mate.

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 and manoeuvred into cells of 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 dead plant cells turn yellow and the yellow patches of dead cells can be seen on the upper side of plant leaves. Unlike other scale insects (Coccoidea), Diaspididae scale insects possess a blind gut with no connection between the stomach and the anal opening.

Walking, and dispersal

The crawler stage of the first instar nymph and the adult males are the only two stages with functional legs. They both have three pairs of legs and antennae. The adult male Serene scale are wingless. The crawler if the main stage for dispersal. Most crawlers walk to other parts of leaves and stems, or to nearby stems and leaves. Some crawlers disperse to other plants; most 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 can walk over leaves and stems in search of females with which to mate.

Adult females and male nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the eggs under the transparent cover of the female scale insects. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMD]

Two adult female Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the eggs and egg shells under the transparent cover of the female scale insects, the two yellow crawlers (mobile first instar nymphs) and a young male. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLX]

First instar (stage) Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the yellow crawler (mobile first instar nymphs) and the three settled first instar scale. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLY]

Nymphs and female Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the adult females with egg shells, yellow crawler (mobile first instar nymphs) and the settled first and second instar scales. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMB]

Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the female second instar nymphs and young adult female scale and the narrow white male second instar nymphs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PME]

Male Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the narrow white felted male scale covers and the red pupa projecting from one. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMI]

Two mature white male scale of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the felted white scale cover with three ridges running the length of the scale and note the reddish wingless male (bottom left). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMF]

Three images of a wingless adult male Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the young female scale (bottom left). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMK]

Male Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on stems of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMH]

A red wingless adult male Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on a stem of Mahoe, Melicytus ramiflorus (Violaceae): note the white male scale covers. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMJ]

Underside (left) and upper side (right) of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female and young nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside: note the yellow areas on the upper side of the leaf that correspond to the areas of the leaf occupied by the adult scale insects. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLQ]

Scale insects require specialist skills for their identification. In many cases Serene scale can be identified on known host plants. The drop-shaped female cover may be almost transparent allowing the pale yellow female body, yellow eggs and white egg shells to be seen. The scale cover may be opaque and cover a pinkish female body. The covers of male are felted white, long and narrow and tricarinate (three lines run the length of the scale cover). The cover of the female is almost transparent when it is living on a leaf, but opaque over a pinkish body when on a stem. The front end of the male and female scales have the oval remains of the earlier nymphal scales, one on the male cover and two on the adult female scale. The young mobile first instar (stage) scale, often called crawlers, are yellow. The wingless adult male is reddish in colour.

Underside (left) and upper side (right) of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female and young nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside: note the yellow areas on the upper side of the leaf that correspond to the areas of the leaf occupied by the adult scale insects. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLQ]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female and male nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae): note the male nymphs are narrow and bright white. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLZ]

Serene scales, Serenaspis minima (Hemiptera: Diaspididae) on leaves and stem of Swamp mahoe, Melicytus micranthus (Violaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLW]

Adult females and male nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the eggs under the transparent cover of the female scale insects. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMD]

Two white male scale of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the felted white scale cover with three ridges running the length of the scale. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMG]

Two mature white male scale of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the felted white scale cover with three ridges running the length of the scale and note the reddish wingless male (bottom left). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMF]

A predator, parasitoid and a fungal pathogen of the Serene scale have been found.

Pathogens

The fungal pathogen, Microcera coccophila, has mainly been found on scale insects in the family Coccidae, but it has been found on other species of Diaspididae.

Parasitoids

Evidence of an unknown species of a parasitoid wasp (Hymenoptera) was found. Adult wasp exit holes were seen in adult and juvenile female scales. Adult wasps have not been reared.

Predators

Red fly larvae belonging to the family Cecidomyiidae were found feeding on eggs and crawlers under the scale cover of adult female scales. The fly larvae may also feed directly on the female scale insects. Other insect predators also may feed on Serene scale.

An adult female and small nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the exit hole in the adult female scale cover made by an adult parasitic wasp. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMA]

Serene scale insects, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note the exit holes made in five small female nymphs by adult parasitic wasps. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMC]

Two red fly larvae (Diptera: Cecidomyiidae) feeding on Serene scale insects, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note that the larvae feed under the scale cover on eggs, nymphs and the body of the female scale. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM2]

One red fly larvae (Diptera: Cecidomyiidae) feeding on an adult female Serene scale insect, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note that the larvae feed under the scale cover on eggs, nymphs and the body of the female scale (left). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM1]

Two images of a red fly larvae (Diptera: Cecidomyiidae) fully exposed after lifting the cover an adult female Serene scale insect, Serenaspis minima (Hemiptera: Diaspididae), on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): note that the larva feeds under the scale cover on eggs, nymphs and the body of the female scale. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM3]

Fly pupa (Diptera: Cecidomyiidae) exposed in its cocoon on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): the fly larva had been feeding on Serene scale insects, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM5]

Two images of the empty fly pupal case (Diptera: Cecidomyiidae) projecting from the cocoon on the underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae): the fly larva had been feeding on Serene scale insects, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM6]

Three images of the adult fly (Diptera: Cecidomyiidae) the larva of which had been feeding on Serene scale insects, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM4]

Several small nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae) with fungal hyphae on underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM9]

Serene scale insects may live on the stems and leaves of trees, shrubs and climbers. Most host plants are native to New Zealand. It is most commonly seen on species of Melicytus. The scale insects may reach very high density on host plant leaves and stems.

Feeding

Adult females and nymphs have sucking mouthparts. Specially shaped rods called stylets are 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 leaf. The stylets are then gradually pushed into the plant and manoeuvred into cells of the plant leaf. 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 dead plant cells turn yellow and the yellow patches of dead cells can be seen on the upper side of plant leaves. Unlike other scale insects they have a blind gut, no join between the stomach and anal opening, so unlike many other scale insects, they cannot excrete honeydew.

Underside of a leaf of Kohekohe, Dysoxylum spectabile (Meliaceae) with Serene scales, Serenaspis minima (Hemiptera: Diaspididae): note the male nymphs are narrow and bright white. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLT]

Underside of a leaf of Large-leaved mahoe, Melicytus macrophyllus (Violaceae) with Serene scales, Serenaspis minima (Hemiptera: Diaspididae): note the male nymphs are narrow and bright white. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLV]

Upper side of a leaf of Large-leaved mahoe, Melicytus macrophyllus (Violaceae) with Serene scales, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMQ]

Upper side of a leaf of Large-leaved mahoe, Melicytus macrophyllus (Violaceae) with adult female Serene scales, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMS]

Underside of a leaf of Large-leaved mahoe, Melicytus macrophyllus (Violaceae) with Serene scales, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMP]

Underside of a leaf of Large-leaved mahoe, Melicytus macrophyllus (Violaceae) with Serene scales, Serenaspis minima (Hemiptera: Diaspididae): note the male nymphs are narrow and bright white. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMR]

Serene scales, Serenaspis minima (Hemiptera: Diaspididae) on leaves and stem of Swamp mahoe, Melicytus micranthus (Violaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLW]

Serene scales, Serenaspis minima (Hemiptera: Diaspididae) on stem of Melicytus obovatus (Violaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLU]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female and male nymphs of Serene scale, Serenaspis minima (Hemiptera: Diaspididae): note the male nymphs are narrow and bright white. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PLZ]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female Serene scales, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMM]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female Serene scales, Serenaspis minima (Hemiptera: Diaspididae): note the male nymph that is narrow and bright white. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PMN]

Underside of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) with adult female Serene scales, Serenaspis minima (Hemiptera: Diaspididae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PM0]

Upper side of a leaf of Mahoe, Melicytus ramiflorus (Violaceae) Serene scale, Serenaspis minima (Hemiptera: Diaspididae) on the underside: note the yellow areas on the leaf that correspond to where adult female scale insects were feeding. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2PML]

Research Project

Evidence of an unknown species of a parasitoid wasp (Hymenoptera) was found. Adult wasp exit holes were seen in adult and juvenile female scales. Adult wasps have not yet been reared. If adult wasps can be reared the number of species of parasitoid and their names and other hosts could be determined.

Henderson RC. 2011. Diaspididae (Insecta: Hemiptera: Coccoidea). Fauna of New Zealand. 66: 1-275.

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.