The bright orange-black colored Harmonia axyridis is more commonly known as the Harlequin ladybird, as they occur in varying color patterns, in their wide range of distribution. Due to its worldwide distribution, the Harlequin ladybird is known by different names in different parts of the world. In North America, the Harmonia axyridis is commonly known as the ladybug or the Asian lady beetle. It is also known as the Halloween lady beetle as it invades American homes in the month October as they prepare for overwintering.
"Harlequin ladybirds are known as Halloween lady beetles as they invade homes in October for overwintering"
In the U.K, this species is known by several names such as Japanese, pumpkin, multivariate and southern ladybird. Therefore, the Harlequin ladybird is sometimes colloquially mentioned as the many-named ladybird in the United Kingdom.
The Harmonia axyridis is more commonly known as the Harlequin ladybird, as they occur in varying color patterns.
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The Harlequin ladybird is capable of growing up to 9 mm in length; due to this it is considered one of the largest species in the Coccinellidae family. This ladybird is much more domed in shape as compared to other beetles. The wing coverings, pronotum (dorsal plate) and head, are perfectly aligned in order to form a complete dome-shaped structure. On the belly side of the body, the Harlequin ladybirds are usually reddish-brown in color.
Based on the color patterns of the dome, the Harlequin ladybird is classified into three distinct types known as the variants succinea, spectabilis and conspicua. The ladybirds of the variant succinea are orange or red in color with several black spots. The black colored ladybirds with four red spots constitute the variant spectabilis while the black ladybirds with two red spots are considered as variant conspicua. The average lifespan of a Harlequin ladybird is between 1 – 2 years and they have a very high survival rate.
The conspicua variant of the harlequin ladybird is black and contain two red spots
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The pronotum (dorsal plate) contains white and black markings that form together a ‘M’ shape. This marking is easily visible on Harlequin ladybirds with different color patterns. Distinction in subspecies of Harlequin ladybirds is quite difficult or impossible due to its wide range of variations in body size and number and size of spots on the elytra.
Habitat & Survival Strategies
Harlequin ladybirds are highly adaptable species of beetles found in a wide range of biotopes such as woodlands, deciduous forests, shrublands, seasonal forests and mountainous forests. They have a voracious appetite for aphids and a bad reputation for invading forests with a large population of aphids. Each Harlequin ladybird preys on approximately 5500 aphids in its lifetime. These ladybirds also feed on eggs and larvae of other insects, causing a serious threat to other insect species that share its habitat.
When the temperature drops during winter, Harlequin ladybirds migrate to overwintering sites, where they spend the time in a dormant state, which is quite similar to the hibernation of mammals. For overwintering, these ladybirds occupy warm, concealed and dark places in their habitat. They also invade human facilities like homes, storages and basements in search for suitable overwintering sites.
Each Harlequin ladybird preys on approximately 5500 aphids in its lifetime.
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The Harlequin ladybird is equipped with a set of defensive tools to defend themselves against different predators that share its habitat. They are capable of delivering a small, harmless bite. The main defensive weapon is a chemical, called isopropyl methoxy pyrazine, that is present in its hemolymph (an interior fluid), which makes the beetle distasteful for most of its predators. When threatened, the beetle also secretes hemolymph through its legs giving rise to a foul odor, which also helps in evading predators.
On the other hand, the high rate of survival of Harlequin ladybirds allows the beetle to rapidly increase the population numbers. However, most insect eating birds are immune to the effects of isopropyl methoxy pyrazine; they do frequently prey on Harlequin ladybirds, but the ladybird forms only a small portion of the predators’ diet. Therefore, predation poses a negligible amount of threat to the population of Harlequin ladybirds.
Reproduction and Life Cycle
A Harlequin ladybird can live for up to 3 years under suitable conditions. Like all beetles, the Harlequin ladybird has four stages in its life cycle: egg, larva, pupa and adult. Harlequin ladybirds mate usually in the month of May. Mating usually takes place nearby rich sources of aphids to secure food availability for the larvae after hatching.
A female Harlequin ladybird can lay more than a thousand eggs during her lifespan.
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During mating, the male Harlequin ladybird climbs on the back of a female and inserts its aedeagus into the female reproductive organ. Fertilization occurs internally and the female lays several small orange colored eggs on twigs, close to a rich source of aphids. The eggs hatch in 4 to 5 days. During harsh seasons females lay a lower number of fertilized eggs to increase the chances of survival for the larvae.
The larva of a harlequin ladybird
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The larva emerges out from the egg and starts to feed on aphids as soon as possible. There are five larval stages in a Harlequin ladybird’s lifecycle. During these stages, the larvae gradually grow in size and develop an orange and black color. The larvae are highly opportunistic feeders and can prey on eggs and larvae of other insects if they don’t find enough aphids. The larval stages are complete within 13 to 14 days after hatching of the eggs.
The pupa sticks to the leaves of trees and shrubs in their habitat.
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The larvae then transform and enter the pupa stage of its lifecycle. The pupa sticks to the leaves of trees and shrubs in their habitat. This stage lasts for up to 5 to 6 days before the adult finally emerges out. The adult reaches sexual maturity within 20 days and can live for up to 3 years. On an average lifespan, each female adult Harlequin ladybird lays over thousand eggs, which is one of the main factors supporting its rapid population growth.
Behavior and Communication
Harlequin ladybirds like to feed alone but they are also known to form large swarms during overwintering. Once the winter passes, these beetles emerge out from their concealed hide-outs and continue their hunting rampage. Aphids are most favorite and the beetles typically feed all day on them. These ladybirds have a large appetite and are highly invasive in nature. They can occupy and multiply in any habitat that provides ample sources of aphids.
With their high survival rate, harlequin ladybirds are highly invasive in nature.
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They do not harm humans, but able to deliver a small bite when provoked. These beetles may become aggressive and bite if there is a lack of food in the homes they invade. They have good eyesight, allowing them to navigate their way back to the same location again and again when removed forcibly. These beetles also communicate with each other using semiochemicals. These secreted chemicals allow ladybirds to locate other members in their neighborhood.
Population and Conservation
The population numbers of the Harlequin ladybirds are quite comfortable, but at the same time of high concern for other species in their habitat. Once native to the continent of Asia, this species of ladybird was artificially introduced to American soil with the idea of controlling the spread of aphids in the fields. This attempt proved to be quite successful, but soon the Harlequin ladybird spread-out and occupied North America completely.
On the Eurasian landmass, the Harlequin ladybird made its way to Europe and the United Kingdom by various means. This species is considered the most invasive species in the United Kingdom as it has occupied and invaded the entire country in less than a decade. Australia and New Zealand are currently unaffected by this lady beetle invasion. But with the increase in international transport, these places are also under serious threat of invasion.
"The harlequin ladybird is considered the most invasive species in the UK as it invaded the country in a decade"
Researchers are looking continuously for methods to control the population of Harlequin ladybirds. These beetles pose a serious threat to other native species as they continuously feed on larva and eggs of other insects in their habitat. However, due to its highly adaptable nature, these ladybirds find a way to survive and multiply very rapidly. No effective methods have been found other than usual pest control methods that can only temporarily keep the ladybirds out from human settlements.
Harlequin ladybirds are used in several greenhouses as a convenient and inexpensive pest control measure
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Though they have a bad reputation for being invasive, the Harlequin ladybirds prove also to be quite useful for humans, when used in a controlled atmosphere. These ladybirds are used in several greenhouses as a convenient and inexpensive pest control measure. They feed on aphids and other insects that are harmful to the crops, thus helping farmers to avoid pests on their farms.
The Harlequin ladybird belongs to the family Coccinellidae of the order Coleoptera. This order consists of numerous species of beetles. Most of the species in the order Coleoptera have two pairs of wings; the front pair is hardened and forms a protective shell for the beetle’s body. Fossil records clearly indicate that these insects evolved as early as 300 million years ago on the landmass of Eurasia.
Approximately 210 million years ago, several distinct families of Coleoptera evolved, giving rise to numerous herbivorous and carnivorous species of insects. However, modern beetles evolved only in the last 50 million years. During this period, landmasses on the earth were quite closer to each other, allowing the exchange of several species between the continents. It is speculated that during this period, beetles spread worldwide, invading new lands of opportunities.
According to anatomical and morphological traits, it is concluded that all the Harlequin ladybirds that exist today have evolved from a single ancestral species. However, very little is known about the evolution of Harlequin ladybirds due to the lack of fossil records. Due to their diverse color patterns and physical characteristics, researchers are yet to extract precise information about this species.
- Harlequin ladybirds have a surprising stable population and are increasing in numbers.
- They have a worldwide distribution and are found on every continent except Australia and Antarctica
- A female Harlequin ladybird can lay more than a thousand eggs during her lifespan.
- A Harlequin ladybird feeds on thousands of aphids in its lifespan of 2 to 3 years.
- This species is considered invasive in many places, where it was once introduced artificially to control the growth of aphids.
- Due to their habit of feeding on larvae and eggs of other insects, they are considered as a threat to other insect species living in their habitat.
- The Harlequin ladybird completely invaded the forests and farms of United Kingdom in less than a decade.
- The ladybirds prove to be very useful for farmers if used in a controlled atmosphere as they can get rid of pests from crops.
- In U.K, this ladybird is sometimes called the many-named ladybird as it is known by several different names around the world.
- They are known to invade human settlements for overwintering. They occupy dark and concealed places and show a tendency to return to the same place again and again.