INTERESTING INSECTS

By N A Martin (2016, revised 2018)

Mealybug ladybird, Mealybug Destroyer

This adventive ladybird was deliberately imported from Australia and released into New Zealand several times from 1897 to 1924 to control mealybugs. It is mainly found in Auckland and Northland as it does not persist in places with cool winters. It occurs on plants infested with mealybugs and scale insects, especially those found on Bunya pine and Norfolk Island pine (both Araucaria species).

Conservation status: Mealybug ladybird is in warmer areas of New Zealand and not threatened. It is a useful biological control agent of some kinds of mealybugs and some scale insects. It also feeds on some native insects.

Adult mealybug ladybirds are black with a brown head, prothorax (area behind the head) and the end of the elytra (wing covers). Under the elytra is a pair of wings used for flying. The underside of the body is also black and brown, brown head, prothroax and abdomen. The small head has a pair of compound eyes and two short brown antennae. Female ladybirds lay small groups of eggs among the cottony egg masses of mealybugs and by scale insects. A larva hatches from each egg. It is covered with white flocculent wax and looks like a woolly mealybug. The three pairs of legs are used for walking. Legs don’t appear to be used for holding prey. The hind end of the larva is used to hold onto the plant surface as it is walking. As the larva grows, it moults (changes skin). There are four larval instars (stages). When the fourth larval instar is fully grown, it attaches itself to a sheltered place on a plant and moults into a pupa. The pupa remains attached to the plant by its hind end and is surrounded by the moulted larval skin. If disturbed, the pupa can wag up and down. Adults hatch from pupae and mate.

Annual cycle

The mealybug ladybirds appear to breed all year in New Zealand. There are probably at least three generations per year in Auckland. The length of time of each life stage depends on temperature, being shorter at higher temperatures. The complete life cycle takes about 31 days at 27°C and 45 days at 21°C. Eggs hatch after 5-6 days at 27°C. Females lay 5-10 eggs per day, for a total of 400-500 eggs in their 50-day life time. Larvae feed on mealybugs for 12-17 days. Adults emerge after 7-10 days, mate and females begin laying eggs after 5 days (Applied Bio-nomics SHEET 250 - CRYPTOLAEMUS).

Walking and flying

Both adult and larval stages of the mealybug ladybirds have three pairs of legs that can be used for walking. The larva can also hold onto the plant surface with rear end of its abdomen, which acts like a sucker. Adults have wings and can fly.

Feeding

The adult and larval mealybug ladybirds eat scale insects, especially mealybugs. The jaws are the primarily structures used for holding and chewing the prey. Legs do not appear to be used for holding food. A single larva can consume 250 small mealybugs before pupation (Applied Bio-nomics SHEET 250 - CRYPTOLAEMUS).

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2863]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), side view. Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDI]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), underside. Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDH]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on mealybugs. © Plant & Food Research. [Image: 2CE3]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on mealybugs. © Plant & Food Research. [Image: 2CDT]

Young larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), in colony of mealybugs (Hemiptera: Pseudococcidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDM]

A fully grown larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2CDX]

Underside of a larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on a mealybug. © Plant & Food Research. [Image: 2CDY]

A large larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), with a colony of small mealybugs. © Plant & Food Research. [Image: 2CE0]

Two pupae of mealybug ladybirds, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), pupa on left with the larval skin removed. © Plant & Food Research. [Image: 2CDW]

Underside of two pupae of mealybug ladybirds, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), pupa on left with the larval skin removed; note the eye spots. © Plant & Food Research. [Image: 2CDV]

Adult mealybug ladybirds have the typical ladybird shape, but are black with a brown head, prothorax (area behind the head) and the end of the elytra (wing covers).

The larvae look like mealybugs being covered in white flocculent wax. They are very mobile and the head and legs can be seen on their underside. The underlying body colour is dark grey. Larvae of several smaller ladybirds also look like mealybugs and could be confused with those of the mealybug ladybird. The underlying body colour of these larvae is orange-brown.

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2863]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), underside. Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDJ]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding in a colony of mealybugs. © Plant & Food Research. [Image: 2CE2]

Top side of a fully grown larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2CE4]

Top side of a fully grown larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2CE5]

Two pupae of mealybug ladybirds, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), pupa on left with the larval skin removed. © Plant & Food Research. [Image: 2CDW]

Adult Loew's ladybird, Scymnus loewi, (Coleoptera: Coccinellidae) 2.0-2.2 mm long. © Plant & Food Research. [Image: 2CDG]

Adult Loew's ladybird, Scymnus loewi, (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2CDE]

Two larvae of Loew's ladybird, Scymnus loewi, (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2CDF]

Adult Dusky lady beetle, Nephus binaevatus (Coleoptera: Coccinellidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LRM]

Adult Dusky lady beetle, Nephus binaevatus (Coleoptera: Coccinellidae) with what may be two eggs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LS0]

Four larvae of Dusky lady beetles, Nephus binaevatus (Coleoptera: Coccinellidae) in a colony of New Zealand flax mealybug, Balanococcus diminutus (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LS1]

Larva of Dusky lady beetle, Nephus binaevatus (Coleoptera: Coccinellidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LRL]

Underside of a larva of Dusky lady beetle, Nephus binaevatus (Coleoptera: Coccinellidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LS3]

Larva of Dusky lady beetle, Nephus binaevatus (Coleoptera: Coccinellidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LRN]

No natural enemies of mealybug ladybirds are known in New Zealand, but a wasp parasitoid, Inkaka quadridentata Giralt, 1939 (Hymenoptera: Pteromalidae) is known in Australia. Ladybird adults and larvae may be eaten by birds, spiders and predatory insects

In spring, adults are regularly in association with Pittosporum psyllid, Trioza vitreoradiata (Maskell, 1879) (Hemiptera: Triozidae). It is likely that they are feeding on the honeydew.

The mealybug ladybird feeds on scale insects (superfamily Coccoidea) from three families, mealybugs (Pseudococcidae), soft scale (Coccidae) and felted scale (Eriococcidae). It is particularly associated with the Australian golden mealybug, Nipaecoccus aurilanatus (Maskell, 1890), found on Bunya pine and Norfolk Island pine (both Araucaria species). The ladybird is reported to feed on aphids and each other.

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on mealybugs. © Plant & Food Research. [Image: 2CDU]

Larvae of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on Long-tailed mealybugs, Pseudococcus longispinus (Hemiptera: Pseudococcidae). © Plant & Food Research. [Image: 2CE1]

Larvae of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on Long egg-sac mealybug, Paracoccus glaucus (Hemiptera: Pseudococcidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDN]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), in colony of Golden mealybug, Nipaecoccus aurilanatus (Hemiptera: Pseudococcidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDL]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), in colony of Pulvinaria mesembryanthemi (Hemiptera: Eriococcidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDP]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), in colony of Pulvinaria mesembryanthemi (Hemiptera: Coccidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2CDQ]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on Karo felted scale, Eriococcus pallidus (Hemiptera: Coccidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2CDR]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), feeding on Karo felted scale, Eriococcus pallidus (Hemiptera: Coccidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2CDS]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), on white pine, Dacrycarpus dacrydioides (Podocarpaceae) and feeding on Kahikatea mealybug, Paraferrisia podocarpi (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LRI]

Adult of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), on Coprosma repens (Rubiaceae) and with mealybugs, Dysmicoccus ambiguus (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2LRJ]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), on Coprosma repens (Rubiaceae) and with remains of mealybugs, Dysmicoccus ambiguus (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SB6]

Larva of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), on Queensland kauri, Agathis robusta (Araucariaceae) and feeding on first instar Golden mealybug, Nipaecoccus aurilanatus (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2LSE]

Larvae of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), on Araucaria hunsteinii (Araucariaceae) and feeding on Golden mealybugs, Nipaecoccus aurilanatus (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2LSF]

Larvae of mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), on Queensland kauri, Agathis robusta (Araucariaceae) and feeding on Golden mealybugs, Nipaecoccus aurilanatus (Hemiptera: Pseudococcidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2LSG]

Diverse habits of 'ladybirds'

Not all ladybirds eat insects; some feed on mites. Other species eat plant leaves and are pests especially in some tropical countries, whereas other ladybirds feed on fungi. One of these, Illeis galbula (Mulsant, 1850), from Australia, feeds on powdery mildew fungi. In New Zealand it is common on pumpkins and other cucurbits, plants that are commonly infected by powdery mildews. A plant feeding ladybird, hadda beetle (Epilachna vigintioctopunctata (Fabricius, 1775)) recently established in Auckland feeds on plants in the Solanaceae (potato family).

Biological control of pests

Biological control of mealybugs and other herbivorous pests can reduce the impact of the pests and the need to use insecticides. Mealybug ladybirds are important predators in gardens and parks, and potentially orchards and plant nurseries. In recent years it has been possible to buy mealybug ladybirds for release in greenhouses and gardens. They are best released as eggs or small larvae. Eggs may need protecting from ants if these are attending the mealybug colony. Some biological control agents keep breeding until all the pests are destroyed, but after the mealybug ladybird larva pupate, the newly emerged adults tend to fly away, presumably to find new colonies of mealybugs or scale insects. This means that additional ladybird larvae may need to be purchased.

If pesticides are needed to control other pests, it is advisable to use chemicals that will have minimal harmful effects on the ladybirds or to use them at a time when the ladybirds are not present.

Applied Bio-nomics SHEET 250 - CRYPTOLAEMUS http://appliedbio-nomics.com/sites/default/files/250-cryptolaemus.pdf (accessed 7 March 2011).

Charles JG 1989. Pseudococcidae, mealybugs (Homoptera). In: Cameron PJ, Hill RL, Bain J, Thomas WP ed. A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874 to 1987. Wallingford, Oxfordshire, UK, CAB International. Pp. 223-236.

Shelton A. A guide to natural enemies in North America. www.biocontrol.entomology.cornell.edu/predators/Cryptolaemus.html (accessed 7 March 2011).

Slipinski A, Hastings A, Boyd B 2007. Ladybirds of Australia. Retrieved April 2011 http://www.ento.csiro.au/biology/ladybirds/ladybirds.htm

Valentine EW 1967. A list of the hosts of entomophagous insects of New Zealand. New Zealand Journal of Science 10(4): 1100-1209.

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

1 November 2018. NA Martin. Changed symbol used for apostrophes.

1 August 2018, NA Martin. Added photo of larva feeding on Dysmicoccus.

1 September 2017, NA Martin. Prey table updated, photos added. Recognition: additional species added.