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

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

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 his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...

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 branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''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-hatch Hatching (french: hachure) is an artistic technique used to create tonal or shading effects by drawing (or painting or scribing) closely spaced parallel lines. (It is also used in monochromatic representations of heraldry to indicate what the t ...

ed" 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 and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

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

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

s that are usually laid in clutches. The

larva A larva (; plural larvae ) 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. ...

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 Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, bo ...

. 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 A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

. 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 Female ( symbol: ♀) is the sex of an organism that produces the large non-motile ova (egg cells), the type of gamete (sex cell) that fuses with the male gamete during sexual reproduction. A female has larger gametes than a male. Females ...

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

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

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 bacteria (''

Wolbachia ''Wolbachia'' is a genus of intracellular bacteria that infects mainly arthropod species, including a high proportion of insects, and also some nematodes. It is one of the most common parasitic microbes, and is possibly the most common reproducti ...

'', ''

Rickettsia ''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "ricke ...

'', and ''

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 distinctiv ...

'') 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 Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

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, greenhouses.. The two-spotted lady beetle was introduced into Australia specifically as a biological control agent.

References

External links

{{Taxonbar , from=Q233024 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