Mealybug ladybird - Cryptolaemus montrouzieri
By N A Martin (2016)
Biostatus and Distribution
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.
Life Stages and Annual Cycle
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.
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.
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 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. Larvae of several smaller ladybirds also look like mealybugs and could be confused with those of the mealybug ladybird.
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). They ladybird is reported to feed on aphids and each other.
|Scientific Name||Common Name||Classification||Reliability Index||Biostatus|
|Balanococcus diminutus (Leonardi, 1918)||New Zealand flax mealybug||Hemiptera: Pseudococcidae||10||endemic|
|Coccus hesperidum Linnaeus, 1758||Brown soft scale||Hemiptera: Coccidae||10||adventive|
|Dysmicoccus ambiguus (Morrison, 1925)||Hemiptera: Pseudococcidae||9||endemic|
|Eriococcus araucariae Maskell, 1879||Felted pine scale||Hemiptera: Eriococcidae||10||adventive|
|Eriococcus pallidus Maskell, 1885||Karo felted scale||Hemiptera: Eriococcidae||10||endemic|
|Nipaecoccus aurilanatus (Maskell, 1890)||Golden mealybug||Hemiptera: Pseudococcidae||10||adventive|
|Paracoccus glaucus (Maskell, 1879)||Long egg-sac mealybug||Hemiptera: Pseudococcidae||10||endemic|
|Parasaissetia nigra (Nietner, 1861)||Nigra scale||Hemiptera: Coccidae||9||adventive|
|Pseudococcus calceolariae (Maskell, 1879)||Citrophilous mealybug||Hemiptera: Pseudococcidae||10||adventive|
|Pseudococcus longispinus (Targioni Tozzetti, 1867)||Long-tailed mealybug||Hemiptera: Pseudococcidae||10||adventive|
|Pulvinaria mesembryanthemi (Vallot, 1829)||Iceplant scale||Hemiptera: Coccidae||10||adventive|
|Saissetia oleae (Olivier, 1791)||Black scale||Hemiptera: Coccidae||10||adventive|
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.