The harlequin ladybird, known scientifically as Harmonia axyridis, is one of the most invasive insect species in the UK. Also referred to as the harlequin ladybug or multicoloured Asian ladybird, it poses a threat to native ladybirds due to its voracious appetite and adaptability. Since its introduction in 2004, it has rapidly spread across the country, particularly in towns and gardens. This article will cover how to identify the harlequin ladybird, where it is commonly found, and most importantly, how to control it.
How to Recognise the Harlequin Ladybird
Identifying the harlequin ladybird can be tricky due to its highly variable appearance. However, there are several key features that can help distinguish it from native UK ladybird species:
Size and Shape
Harlequin ladybirds are typically larger than many native ladybirds, measuring between 7 and 8 mm in length. They have a dome-shaped body, which is rounder and more robust than some of the smaller native species.
Colour Variations
The harlequin ladybird is incredibly variable in terms of colour and pattern. The most common forms found in the UK are orange or red with 15 to 21 black spots, or black with two or four red or orange spots. However, they can also be pale yellow or black with other spot combinations.
Distinctive Pronotum Pattern
One of the most reliable features for identifying the harlequin ladybird is the white or cream pronotum (the area behind the head), which often has a black M-shaped mark or two curved lines. This pattern is one of the easiest ways to differentiate it from native species.
Brown Legs
Another distinguishing characteristic is the brown legs of the harlequin ladybird, which is less common among native UK ladybirds.
Larvae and Pupa
Harlequin ladybird larvae are black and spikey, with two distinctive orange stripes. They can grow up to 10 mm in length. The pupa is dark with some orange or red markings and is immobile, usually found attached to plant surfaces.
Where is the Harlequin Ladybird Found in the UK?
Since its introduction to the UK in 2004, the harlequin ladybird has become widespread, particularly in urban areas and gardens. It has been recorded across England, Wales, and is now spreading into Scotland. The species is highly adaptable and can thrive in various habitats, from gardens and parks to woodlands and farmlands. It is commonly found on deciduous trees such as sycamore and willow, as well as on low-growing plants like nettles.
During the autumn months, harlequin ladybirds tend to gather in large numbers to hibernate. They often enter homes and buildings to find sheltered spaces for overwintering. This behaviour makes them a nuisance for homeowners, as they can be found clustering in attics, window sills, and behind walls.
How to Avoid the Harlequin Ladybird
Preventing the harlequin ladybird from entering homes is one of the best ways to manage their presence. They are particularly drawn to light-coloured buildings, where they seek out cracks and crevices to shelter in during the winter months. To avoid infestations:
- Seal entry points: Inspect and seal cracks around doors, windows, and foundations where the ladybirds could enter. Using weatherstripping or caulking is a practical solution to close gaps.
- Install window screens: Fitting fine-mesh screens on windows and vents can also help prevent their entry.
- Trim vegetation: Keeping trees and shrubs away from the exterior walls of your home can reduce their chances of finding an entry point.
How to Control and Get Rid of the Harlequin Ladybird
The harlequin ladybird can become a significant nuisance, especially when they gather in large numbers inside homes during autumn. While they are not harmful to humans, they can release a yellowish, foul-smelling fluid known as reflex blood when disturbed. This liquid can stain fabrics, walls, and furniture, making them an undesirable guest.
Vacuuming
One of the most effective ways to remove harlequin ladybirds from inside your home is by vacuuming. It’s recommended to use a vacuum with a nylon stocking placed inside the hose to catch the beetles, preventing them from being crushed and releasing reflex blood. After vacuuming, the beetles can be safely released outside.
Trapping
There are light-based traps designed to attract and capture ladybirds indoors. These traps work by luring the beetles into a removable container, making it easy to dispose of them without causing a mess.
Outdoor Control
In gardens, the harlequin ladybird can be both a pest and a predator of common garden pests like aphids. However, its aggressive feeding behaviour can pose a threat to native ladybird populations. Chemical insecticides are generally not recommended for use against harlequin ladybirds, as these products may also harm beneficial insects, including native ladybirds. Biological control methods, such as introducing predators like soldier bugs, are currently under investigation, though not widely available yet.
Managing Large Aggregations
During autumn, harlequin ladybirds often form large aggregations as they seek overwintering sites. These aggregations can be particularly noticeable on the south-facing sides of buildings where the insects are attracted to warmth. If they begin to cluster on or inside homes, it’s important to remove them early before the numbers become overwhelming.
In some cases, exclusion methods like installing insect screens or sealing entry points are the most effective. Once inside, the same vacuuming and trapping techniques used for smaller infestations can be employed.
The Life Cycle of the Harlequin Ladybird
The harlequin ladybird’s life cycle is one of the factors that make it such a successful invasive species. From egg to adult, the life cycle takes about a month in warm weather, allowing for several generations to be produced within a year.
Egg Stage
Female harlequin ladybirds lay their eggs in clusters on plants, often on leaves where aphid populations are high. Each female can lay over a thousand eggs in her lifetime, contributing to rapid population growth.
Larvae Stage
After hatching, the larvae immediately begin feeding on aphids and other insects. The larvae stage lasts for about two to three weeks, during which time the larvae grow quickly, feeding voraciously on whatever prey they can find. Their ability to consume large quantities of food gives them a competitive advantage over native species.
Pupa Stage
Once the larvae have matured, they pupate, transforming into adult ladybirds. The pupal stage lasts about a week, and the adults emerge ready to continue the cycle.
Adult Stage
As adults, harlequin ladybirds are highly mobile and adaptable. They feed on a wide range of prey, including aphids, scale insects, and even the eggs and larvae of other ladybirds. This predatory behaviour makes them a threat to native ladybird species, particularly the two-spot ladybird, which has seen a decline in population due to competition from the harlequin ladybird.
Where Do Harlequin Ladybirds Live?
Harlequin ladybirds are highly adaptable and can be found in a wide range of habitats across the UK. They are particularly prevalent in towns, gardens, parks, and woodland areas where aphid populations are abundant. In agricultural areas, they can be found on crops and in orchards, where they were originally introduced as a biological control for aphids.
In urban areas, harlequin ladybirds are commonly found on buildings during autumn when they seek out warm, sheltered places to overwinter. This behaviour often leads to infestations in homes, especially in lofts, window sills, and wall cavities.
Impact on Native Species
One of the major concerns with the spread of the harlequin ladybird is its impact on native UK species. The harlequin ladybird’s ability to out-compete other ladybirds for food, combined with its tendency to feed on the eggs and larvae of other ladybirds, has led to a decline in some native species, particularly the two-spot ladybird. Monitoring of this invasive species is ongoing, and conservation efforts are focused on understanding its full impact on UK biodiversity.