Invasive Alien Species in Northern Ireland

Harmonia axyridis, Harlequin ladybird

Harmonia axyridis Pallas, 1773
 
Introduction
The harlequin is a large black-spotted reddish or orange ladybird native to eastern China and Japan.
The harlequin has been introduced to many parts of the world including Europe to control pest greenfly, principally in glasshouses. From these origins it has spread into the wild and damaged ladybird populations native to other regions.
 
Description
The harlequin is also known as the multicoloured Asian ladybird and the Halloween ladybird. It has a very variable appearance:
  • Size and shape : large (5-8mm or about 1/4 inch), round
  • Elytra (wing case) ground colour: pale yellow-orange, orange-red, red or black; highly variable
  • Elytra pattern: many large spots (or none); 0-21 orange-red or black spots, or grid pattern; highly variable
  • Most common forms in UK : orange with 15-21 black spots: black with two or four orange or red spots
  • Pronotum pattern: white or cream with up to five spots or fused lateral spots forming two curved lines, M-shaped mark or solid trapezoid.

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    Country of origin
    The harlequin is an arboreal ladybird native to northern and eastern Asia including China and Japan.
     
    Current distribution
    It was imported to the United States repeatedly in the twentieth century but became established in the wild only in the 1980s. It has spread from the original area of naturalisation in the south-eastern US into Canada and most other parts of the US. It is now the most abundant ladybird there, to the detriment of many native species. Despite the North American experience, the animal has since been imported repeatedly into Italy and elsewhere in Europe. It has now naturalised and is common in Germany (2000), Holland (2002) and Belgium (2002). Numbers in The Netherlands and Belgium increased greatly in June-July 2004 despite it being a 'bad' year for aphids and other ladybirds. Recently it has reached Britain (September 2004) and by June 2005 had spread to most of the southern counties with reports from as far north as Lancashire (see Map). The first British specimen was taken by Ian Wright who found it in the grounds of the White Lion public house at Sible Hedingham, north Essex on 19 September 2004. It was then reported from other parts of greater London and from elsewhere in the south-east. Despite a flood of mistaken claims and misidentifications, a substantial number of verified records are now available for the whole of south-east England with a scatter of outliers as far west as Devon and as far north as Lancashire.
     
    Location in Ireland
    Not so far recorded in Ireland.
     
    Life cycle
    It is believed that females overwinter in protected sites unmated, with the majority of the population mating later in the spring. Eggs generally hatch in three to five days. The larval stage lasts 12 to 14 days, and the pupal stage, which takes place on leaves, lasts five to six days. In cool spring weather, development from egg to adult can take 36 days or longer. After emergence, adults can live as long as two to three years under optimal conditions.
     
    Wildlife and habitat impacts
    The reason for the original and for all subsequent introductions is a perception that the harlequin is a very efficient biological control organism, particularly with respect to aphid infestations of food crops. However, highly invasive behaviour and a very wide dietary and ecological range allow it to potentially eat all the aphids in an area, out-competing native ladybirds whose populations decline by starvation. Some formerly common species in Canada are now rare.
    When the aphid supply fails, it will predate other invertebrates – hoverflies, lacewings, butterflies, thrips, etc. Many of these are beneficial to agriculture, but are put at risk. This scenario has been experienced in North America and is under way in Europe. The already serious problems caused by harlequin naturalisation on a continental scale could be magnified on small islands such as Britain and Ireland.
     
    Human impacts
    A particular problem in the US has been mass hibernation of the adults in and around houses where they constitute a considerable nuisance. In many areas it is recommended that ladybirds be prevented from getting into buildings by careful sealing of cracks and openings around windows, doors and utility pipes with silicone rubber or similar sealant. Interior temperatures in houses often promote continuous activity and since up to 20,000 may occur in any one locality, the problems are obvious. When alarmed, ladybirds discharge a yellow fluid due to reflex bleeding from the leg joints that will stain walls, paint, and fabrics, and that has an unpleasant odour. Rough handling, including vacuuming, are therefore not recommended for disposal and prevention seems to be much better than attempting to remove them once established!
     
    Key vectors
    Natural migration, by flying and dispersal of adult insects, is the main means of spread.
     
    What you can do as an individual
    Members of the public have a role to play here by reporting suspected occurrences to CEDaR, Botany Department, Sciences Division, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down BT18 0EU. Tel: 028 9039 5256, email Damian.McFerran[at]nmni.com or to the author of this article (roy.anderson[at]ntlworld.com).
     
    Advice to specific groups relevant to this species
    Apart from the reporting of any suspected occurrences to regulatory authorities, no further action is recommended. Suspect ladybirds should not be destroyed until seen by an expert.
     
    Management measures
    In Japan, Harmonia axyridis is primarily a forest species and is common on various aphid-infested trees and bushes such as maple, walnut, willow, and rose. It is also an important predator of various destructive scales in Japan and mainland China. An adult is capable of consuming 90 to 270 aphids per day, and each larva can consume 600 to 1,200 aphids during its development.
    Periodic large, and even explosive, population increases are probably caused by the availability and abundance of prey (predominantly aphids and scales), inability of native ladybirds to compete, and a lack of natural enemies.
    It has been postulated that in affected areas the population will eventually fall back to lower, more balanced, levels as prey decreases and natural enemies increase. This should not be relied upon, however, and some assistance in the form of artificially introduced parasitoids or predators may be necessary to stem the tide of damage to native species of ladybird, that is, a form of biological control. At present research is at an early stage and no proven method of control exists.
     
    Further information
    Links
    UK Ladybird Survey
    http://www.ladybird-survey.org/
    Harlequin Ladybird Survey
    http://www.harlequin-survey.org/
    UK Safari — ladybirds
    http://www.uksafari.com/ladybirds.htm
     
    Literature
    Majerus, M. and Kearns. P. (1989). Ladybirds. Naturalists' Handbooks 10. Richmond Publishing, Surrey.
    Majerus, M., Strawson, V. & Roy, H. (2006) The potential impacts of the arrival of the harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in Britain. Ecological Entomology 31: 207-215.
     
    See the Invasive Species Ireland web site for further information -
    http://www.invasivespeciesireland.com/mostunwanted/
     
    Text written by:
    Dr Roy Anderson