Two-spotted lady beetle
Encyclopedia
Adalia bipunctata, commonly known as the two-spot ladybird, two-spotted ladybug or two-spotted lady beetle, is a carnivorous beetle
of the family Coccinellidae
that is found throughout the holarctic
region. It is very common in western and central Europe
and North America
. It is used as a biological control agent.
in his 18th century work, Systema Naturae
, its original name was Coccinella bipunctata. Its specific name from the Latin
bi- "two", and punctata "spotted".
The two-spotted lady beetle's life cycle starts with egg
s that are usually laid in clutches. The larva
e hatches from the egg by biting a hole in it. The larvae look very different from the adults: they have elongated, grey, soft bodies with six legs but no wings. They are cannibalistic. Larvae go through four larval stages: by eating they grow and at some point they shed their old skin and appear in a new one in which they can grow more. The last larval stage is approximately the size of an adult beetle. Once it has eaten enough, the larvae attach themselves to a substrate
and moult into a pupa
. Inside the pupa, the adult develops. Finally the adult ecloses from the pupa.
. In these populations, 80-90% of the offspring of a female are female. The cause of this anomaly is the presence of symbiotic bacteria
living within the gametic
cells of the female lady beetles. The bacterium is too large to live in the male gametes (sperm
), so the bacterium can be transmitted to the next generation only through female gametes. When it ends up in a male, it will die when the male dies. Therefore, it kills most of the male embryos in the newly laid eggs. These dead embryos then serve as food for their sisters when they emerge from their eggs. This trait is associated with a variety of different bacteria (Wolbachia
, Rickettsia
, Spiroplasma
), which are present in between 0 and 20% of females, depending on locality.
s in, for example, greenhouse
s.. The Two-spotted lady beetle was introduced into Australia
specifically as a biological control agent.
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
of the family Coccinellidae
Coccinellidae
Coccinellidae is a family of beetles, known variously as ladybirds , or ladybugs . Scientists increasingly prefer the names ladybird beetles or lady beetles as these insects are not true bugs...
that is found throughout the holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
region. It is very common in western and central Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It is used as a biological control agent.
Taxonomy
The two-spotted ladybird was one of the many species originally described by LinnaeusCarolus Linnaeus
Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
in his 18th century work, Systema Naturae
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...
, its original name was Coccinella bipunctata. Its specific name from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
bi- "two", and punctata "spotted".
Phenotypic variations
The most familiar form of the two-spot ladybird beetle is the red one with the two black spots. However, there also exists a black form with red spots on it. In addition, there are intermediate forms, but they occur only rarely in nature.Life cycle
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s that are usually laid in clutches. The larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e hatches from the egg by biting a hole in it. The larvae look very different from the adults: they have elongated, grey, soft bodies with six legs but no wings. They are cannibalistic. Larvae go through four larval stages: by eating they grow and at some point they shed their old skin and appear in a new one in which they can grow more. The last larval stage is approximately the size of an adult beetle. Once it has eaten enough, the larvae attach themselves to a substrate
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
and moult into a pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
. Inside the pupa, the adult develops. Finally the adult ecloses from the pupa.
Sex ratio anomalies
Symbiosis
In some populations, the majority of the beetles are femaleFemale
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
. In these populations, 80-90% of the offspring of a female are female. The cause of this anomaly is the presence of symbiotic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
living within the gametic
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
cells of the female lady beetles. The bacterium is too large to live in the male gametes (sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
), so the bacterium can be transmitted to the next generation only through female gametes. When it ends up in a male, it will die when the male dies. Therefore, it kills most of the male embryos in the newly laid eggs. These dead embryos then serve as food for their sisters when they emerge from their eggs. This trait is associated with a variety of different bacteria (Wolbachia
Wolbachia
Wolbachia is a genus of bacteria which infects arthropod species, including a high proportion of insects , as well as some nematodes. It is one of the world's most common parasitic microbes and is possibly the most common reproductive parasite in the biosphere...
, Rickettsia
Rickettsia
Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...
, Spiroplasma
Spiroplasma
Spiroplasma is a genus of Mollicutes, a group of small bacteria without cell walls. Spiroplasma shares the simple metabolism, parasitic lifestyle, fried-egg colony morphology and small genome of other Mollicutes, but has a distinctive helical morphology, unlike Mycoplasma. It has a spiral shape...
), which are present in between 0 and 20% of females, depending on locality.
Parasitism
The two spot ladybird also carries a sexually transmitted infection in Central and Eastern Europe. The infection is an ectoparasitic mite Coccipolipus hippodamiae that transfers between male and female (and female and male) during copulation . The infection sterilizes female two spot ladybirds, and at some points of the year, up to 90% of adult 2-spots become infected .As biological control agent
A. bipunctata is used as a localised biological control agent against aphidAphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s in, for example, greenhouse
Greenhouse
A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...
s.. The Two-spotted lady beetle was introduced into Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
specifically as a biological control agent.