| Harmonia axyridis | |
|---|---|
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Polyphaga |
| Infraorder: | Cucujiformia |
| Family: | Coccinellidae |
| Genus: | Harmonia |
| Species: | H. axyridis |
| Binomial name | |
| Harmonia axyridis (Pallas, 1773) | |
| Synonyms | |
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Harmonia axyridis is a largelady beetle or ladybug species that is most commonly known as theharlequin,Asian, ormulticoloured Asian lady beetle. This is one of the most variable species in the world, with an exceptionally wide range of colour forms.[2][better source needed] It is native to easternAsia, but has been artificially introduced toNorth America andEurope to controlaphids andscale insects. It is now common, well known, and spreading in those regions, and has also established in Africa and widely across South America. This species is conspicuous in North America, where it may locally be known as theHalloween beetle, as it often invades homes during October tooverwinter.[3]
When the species first arrived in the UK, it was labelled in jest as the "many-named ladybird" due to the great quantity of vernacular names. Among those already listed other names include multivariate, southern, Japanese, and pumpkin ladybird.[4]
Harmonia axyridis is a typicalcoccinellid beetle in shape and structure, being domed and having a "smooth" transition between itselytra (wing coverings),pronotum, and head. It ranges from 5.5–8.5mm in size. The common colorform, f. "succinea", is orange or red in colouration with 0–22 black spots of variable size. The other usual forms, f. "conspicua" and f. "spectabilis", are uniformly black with, respectively, two or four red markings. The pronotum is white with variable black patterning, ranging from a few black spots in an M formation to almost entirely black. The underside is dark with a wide reddish-brown border.
However, numerous other forms have also been recorded. Extreme forms may be entirely black, or feature complex patterns of black, orange and red.
The large size of this species is usually the first clue to its identification.[5][6] Despite variation, this species does not generally overlap in pronotal or elytral pattern with any other species, except in unmarked orange or red forms. In Europe it is similar to the much smallerAdalia decempunctata, while in America it is similar to the much smallerMulsantina picta and spotless forms ofAdalia bipunctata. When identification is difficult, the underside pattern usually enables a reliable conclusion.[2] Identification is most simple for the common forms, while less common varieties may take longer to identify.[7] They always have reddish-brown legs and are obviously brown on the underside of the abdomen, even in themelanic colour forms.
Harmonia axyridis is native to easternAsia from centralSiberia,Kazakhstan, andUzbekistan in the west, throughRussia south to theHimalayas and east to thePacific coast andJapan, includingKorea,Mongolia,China, andTaiwan. As a voracious predator, it was identified as abiocontrol agent foraphids andscale insects. Consequently, it has been introduced intogreenhouses,crop fields, andgardens in many countries, including theUnited States and parts ofEurope. The species is now established in North America (United States,Canada,Mexico), Central America (Guatemala,Honduras,Costa Rica,Panama), South America (Brazil,Venezuela,Colombia,Ecuador,Peru,Argentina,Chile), Europe (Italy,Spain, theUnited Kingdom,Denmark,Sweden,Norway,Finland, theNetherlands,Belgium,Luxembourg,France,Germany, theCzech Republic,Slovakia,Hungary,Romania,Serbia,Croatia,Bosnia and Herzegovina,Poland),Israel,New Zealand, andSouth Africa.[8]
This species spread across continents because of human-mediated processes. They became established in North America as the result of introductions into the United States in an attempt to control the spread of aphids. In the last three decades, this insect has spread throughout the US and Canada, and has been a prominent factor in controlling aphid populations. The first introductions into the US took place as far back as 1916. The species repeatedly failed to establish in the wild after successfully controlling aphid populations, but an established population of beetles was observed in the wild nearNew Orleans, Louisiana, in about 1988. In the following years, it quickly spread to other states, being occasionally observed in theMidwest within five to seven years and becoming common in the region by about 2000. The species was also established in the Northwest by 1991, and the Northeast by 1994, aided by additional introductions from the native range, rather than just reaching there from the Southeast. Reportedly, it has heavily fed onsoybean aphids (which recently appeared in the US after coming fromChina), supposedly savingfarmers vast sums of money in 2001.[citation needed]
Worldwide routes of propagation ofH. axyridis were described withgenetic markers in 2010.[9] The populations in eastern and western North America originated from two independent introductions from the native range.[9] The South American and African populations both originated independently from eastern North America.[9] The European population also originated from eastern North America, but with substantial genetic admixture with individuals of the European biocontrol strain (estimated at 40%).[9]
The species is widely considered to be one of the world's mostinvasive insects,[10][11] partly due to their tendency to overwinter indoors and theunpleasant odor and stain left by their bodily fluids when frightened or crushed, as well as their tendency to bite humans.[10] In Europe it is currently increasing to the detriment of indigenous species,[10] its voracious appetite enabling it to outcompete and even consume other ladybirds.[10] The harlequin ladybird is also highly resistant to diseases that affect other ladybird species, and carries amicrosporidian parasite to which it is immune, but that can infect and kill other species.[11] Native ladybird species have experienced often dramatic declines in areas invaded byH. axyridis.[12] In 2015, it was declared the fastest-invading species in the UK, spreading throughout the country after the first sighting was confirmed in 2004.[13]
In addition to its household pest status,[14] the harlequin has been reported to be a minor agricultural pest that has been inadvertently harvested with crops inIowa,Ohio,New York State, andOntario,[15] causing a detectable and distinctly unpleasant taste, known as "lady beetle taint".[16] In particular, contamination of grapes by the beetle has been found to alter the taste of wine.[17]
Harmonia axyridis becomes dormant in cooler months, though it will move around whenever the temperature reaches about 10 °C (50 °F). Because the beetles will usecrevices and other cool, dry, confined spaces to overwinter, significant numbers may congregate inside walls if given a large enough opening.
Large aggregations are often seen in autumn. The beetles have pheromones to signal to each other. However, many aggregation cues are visual, picking out sites at both long (light-coloured structures that are distinct from their surroundings) and short (pre-existing aggregations to join) distances. Non-volatile long-chain hydrocarbons laid down by previous aggregations also play a significant role in site selection. Both visual and hydrocarbon cues are more important than volatile pheromones.
They often congregate in sunlit areas because of the heat available, so even on fairly cold winter days, some of the hibernating beetles will "wake up" because of solar heating. Large populations can be problematic because they can formswarms and linger in an area for a long time. The beetles can form groups that stay in upper corners of windows. This beetle has been also found to be attracted to dark screening material for its warmth. It has good eyesight; it will return from a location to which it is removed, and is known to give a small bite if provoked.[18]
Harmonia axyridis, like other ladybeetles or ladybirds, usesisopropyl methoxy pyrazine as adefensive chemical to deter predation, and also carries this chemical in itshemolymph at much higher concentrations than many other ladybeetle species, along with species-/genus-specific defensive compounds such as harmonine. These insects will "reflex bleed" when agitated, releasing hemolymph from theirlegs. The liquid has a foul odour (similar to that of deadleaves), a bitter taste, and can stain porous materials. Some people haveallergic reactions, includingallergic rhinoconjunctivitis when exposed to these beetles.[3] Occasionally, the beetles will bite humans,[3] presumably in an attempt to acquire salt, although many people feel a pricking sensation as a beetle walks across the skin. Bites normally do no more harm than cause irritation, although a small number of people are allergic to bites.[19] Their natural predators includebirds,spined soldier bugs,ants (including the also invasiveSolenopsis invicta) and other coccinellids, including fellowHarmonia axyridis.[20]
These beetles can be difficult to identify because of their variations in color, spot size, and spot count of the elytra. The easiest way to identifyH. axyridis f. succinea is to look at the pronotum and see whether the black markings look like a letter "W" or "M". This species has more white markings on the pronotum than have most native North American species, though this feature is not useful when attempting to separate it from species in other parts of the world.
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Numerous methods of control have been investigated in areas where this beetle has been introduced and causes a threat to native species and biodiversity and to the grape industry. Methods of control include insecticides, trapping, removal of aggregates of beetles, and mechanically preventing entry to buildings.[21] Methods under development involve the investigation of natural parasites and pathogens, including the use of parasitic sexually transmitted mites and fungal diseases.[22]
The best methods for dealing withH. axyridis in private homes involve sealing openings they may enter.[23] Sweeping and vacuuming are considered effective methods for removing them from homes, though this should be done carefully so as not to triggerreflex bleeding. Anylonstocking placed inside the vacuum cleaner's hose, secured with arubber band, allows the beetles to be "bagged" rather than collected inside the machine.[24] A trap designed for indoor use was developed which attracts the beetles with a light and seals them in a removable bag.[23]
Harmonia axyridissecretes a number of defensive compounds, one of which,(9Z,17R)-9-Octadecene-1,17-diamine (harmonine) has been isolated from its hemolymph. This molecule has been reported to have broad-spectrum antimicrobial activity that includes human pathogens. Antibacterial activity is most pronounced against fast-growingmycobacteria andMycobacterium tuberculosis, and the growth of bothchloroquine-resistantPlasmodium falciparum strains is also inhibited;[25] causative agents oftuberculosis andmalaria respectively.
Media related toHarmonia axyridis at Wikimedia Commons