''Adalia bipunctata'', the two-spot ladybird, two-spotted ladybug or two-spotted lady beetle, is a carnivorous

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

of the family Coccinellidae that is found throughout the

holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...

region. It is very common in western and central Europe. It is also native to North America but it has heavily declined in many states and provinces. It is commonly introduced and imported as a biological control agent.

Taxonomy

The two-spotted ladybird was one of the many species originally described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in his 1758 10th edition of ''Systema Naturae''; its original name was ''Coccinella bipunctata''. Its specific name is from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''bi-'' "two", and ''punctata'' "spotted".

Description

''Adalia bipunctata'' is a small Coccinellid that can feature any one of a large selection of red and black forms. Some forms are similar to '' Mulsantina picta'', but the two white spots on the head of ''Adalia'' (in contrast with a large white region or more than two spots) readily separate it. Additionally ''Adalia'' is entirely black on the ventral surface with black legs, which helps rule out any other options. The two-spotted ladybird is highly variable in many parts of its native range. The most familiar form, form ''typica'' with two black spots on a red base, is common throughout. A melanistic form that is black with four or six red spots is uncommon, but not rare, while the truly melanistic form ''purpurea'' is exceedingly rare. In North America the species shows the most variation, with several forms that do not occur elsewhere including a spotless form, a four-banded form, a nine to twelve spotted form, and a " cross-hatched" form. In addition, there are intermediate forms such as form ''annulata'', but they occur rarely.

Prey

Two-spotted lady beetles feed on

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

s and other small insects. However, the sterile soldiers within colonies of aphids such as the gall-forming '' Pemphigus spyrothecae'', can attempt to protect the aphid colony by fighting this species.

Life cycle

The two-spotted lady beetle's life cycle starts with eggs that are usually laid in clutches. The

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

hatches from the egg by biting a hole in it. The larva looks very different from an adult; it has an elongated, grey, soft body with six legs but no wings. They are cannibalistic. A larva goes through four larval stages: by eating it grows and at some point it sheds its old skin and appears in a new one in which it can grow more. The last larval stage is approximately the size of an adult beetle. Once it has eaten enough, the larva attaches itself to a substrate and moults into a pupa. Inside the pupa, the adult develops. Finally the adult ecloses from the pupa. File:Snodgrass Adalia bipunctata.jpg, Life cycle of ''Adalia bipunctata''. Illustration from ''Insects, Their Way and Means of Living'' by R. E. Snodgrass File:Two-spotted lady beetles (Adalia bipunctata) mating.JPG, Spotted lady beetles mating File:Adalia bipunctata 1475004.jpg, Larva File:Adalia bipunctata 1475003.jpg, Pupa File:Coccinellidae - Adalia bipunctata.JPG, The adult beetle File:Newborn ladybirds (8285582556).jpg, Newborns

Sex ratio anomalies

Symbiosis

In some populations, the majority of the beetles are

female An organism's sex is female ( symbol: ♀) if it produces the ovum (egg cell), the type of gamete (sex cell) that fuses with the male gamete (sperm cell) during sexual reproduction. A female has larger gametes than a male. Females and ...

. In these populations, 80-90% of the offspring are female. The cause of this anomaly is the presence of

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

living within the gametic cells of the female lady beetles. The bacterium is too large to live in the male gametes (

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile 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 bacteria ('' Wolbachia'', '' Rickettsia'', and '' Spiroplasma'') 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 two spots become infected.Webberley, K. M.; Buszko, J.; Isham, V. & Hurst, G. D. D. (2006). "Sexually transmitted disease epidemics in a natural insect population". ''Journal of Animal Ecology''. 75 (1): 33-43:

As biological control agent

''A. bipunctata'' is used as a localised biological control agent against

s in, for example,

greenhouse A greenhouse is a structure that is designed to regulate the temperature and humidity of the environment inside. There are different types of greenhouses, but they all have large areas covered with transparent materials that let sunlight pass an ...

s.. The two-spotted lady beetle was introduced into

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

specifically as a biological control agent.

References

External links

{{Authority control Biological pest control beetles Insects used as insect pest control agents Beetles of New Zealand Coccinellidae Beetles described in 1758 Taxa named by Carl Linnaeus National symbols of Latvia