lady beetle

Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they are not true bugs. Many of the species have conspicuous aposematic colours and patterns, such as red with black spots, that warn potential predators that they are distasteful.

The majority of the more than 6,000 described species are generally considered beneficial insects, because many prey on herbivorous hemipterans such as aphids or scale insects, which are agricultural pests. Many coccinellids lay their eggs directly in aphid and scale insect colonies, ensuring their larvae have an immediate food source. However, some species such as the herbivorous Mexican bean beetle are agricultural pests.

Etymology

The name ''coccinellids'', created by Pierre André Latreille, is derived from the Latin word ''coccineus'' meaning "scarlet". The name ''ladybird'' originated in Britain where the insects became known as "Our Lady's bird" or the Lady beetle. Mary (Our Lady) was often depicted wearing a red cloak in early paintings, and the spots of the seven-spot ladybird (the most common in Europe) were said to symbolise her seven joys and seven sorrows. In the United States, the name was popularly adapted to ''ladybug''. Common names in some other European languages share associations; for example, the German name ''Marienkäfer'' translates to Marybeetle or ladybeetle. Entomologists prefer the names ladybird beetles or lady beetles to avoid confusion with the true bugs.

Description

Most coccinellids have round to elliptical, dome-shaped bodies with six short legs. They are often conspicuously coloured yellow, orange, or red with small black spots on their wing covers, with black legs, heads and antennae. There is, however, great variation in these colour patterns. For example, a minority of species, such as ''Vibidia duodecimguttata'', a twelve-spotted species, have whitish spots on a brown background. Coccinellids are found worldwide, with over 6,000 species described.

File:BIEDRONA mirrored, cropped.png, ''Coccinella septempunctata'', black spots on red
File:Psyllobora.vigintiduopunctata.6920.jpg, ''Psyllobora vigintiduopunctata'', black spots on yellow
File:Coccinellidae - Vibidia duodecimguttata-1 (cropped).JPG, ''Vibidia duodecimguttata'', whitish spots on brown
File:Brumoides suturalis (10.3897-zookeys.803.22543) Figure 16.jpg, ''Brumoides suturalis'', longitudinally striped
File:Rhyzobius chrysomeloides.jpg, ''Rhyzobius chrysomeloides'', brown, unspotted

Evolution

Fossil history

The Coccinellidae are sparsely preserved in the fossil record. Although molecular clock estimates have placed their origin in the Cretaceous, the oldest fossils of the group are known from the Oise amber of France, dating to the Early Eocene (Ypresian) around 53 million years ago, which belong to the extant genera ''Rhyzobius'' and '' Nephus''. The greatest number of fossils comes from the younger Eocene Baltic amber, including members of the extant genera '' Serangium'' and ''Rhyzobius'' as well as extinct genera belonging to the tribes Microweiseini (''Baltosidis'') and Sticholotidini (''Electrolotis'').

Phylogeny

The Coccinellidae are within the superfamily Coccinelloidea, which in turn is part of the infraorder Cucujiformia, a group containing most of the plant-eating beetles. The ladybirds form the majority of the species in the Coccinelloidea; many of the rest are small bark beetles. The Cleroidea, a superfamily of mainly hairy beetles with soft elytra, is the sister group to the Coccinelloidea.

The internal phylogeny of the Coccinellidae has been studied using gene sampling across many species by LiHeng and colleagues in 2021. It identified three subfamilies including one newly-identified, the Monocoryninae. All three subfamilies were strongly supported, but the study noted that at lower classification levels, while the tribes are mostly monophyletic, their relationships are only weakly supported. The study suggests that the crown group appeared some 143 Mya in the Early Cretaceous, and that the group diversified rapidly during the Late Cretaceous, perhaps because the growth in diversity of angiosperm plants then encouraged the radiation of Sternorrhyncha such as aphids on which ladybirds could feed.

Biology

Life cycle

Predatory ladybirds are usually found on plants which harbour their prey. They lay their eggs near their prey, to increase the likelihood the larvae will find food easily. In ''Harmonia axyridis'', eggs hatch in three to four days from clutches numbering from a few to several dozen. The larvae pass through four instars, over a period of 10 to 14 days, the time taken depending on resource availability, after which pupation occurs. After a teneral period of several days, the adults become reproductively active and are able to reproduce again later, although they may become reproductively quiescent if they emerge late in the season. Total life span is one to two years on average.

Most species overwinter as adults in diapause, aggregating on the south sides of large objects such as trees or houses during the winter months, and dispersing in response to increasing day length in the spring.

File:Mating ladybugs.jpg, Adults mating
File:MarienkäferEier 03.JPG, Eggs (match for scale)
File:Ladybug larva (Coccinellidae).jpg, Larva
File:Pupa de coccinélido, Hartelholz, Múnich, Alemania, 2020-06-27, DD 285-298 FS.jpg, Pupa

Diet

Coccinellids are best known as predators of Sternorrhyncha such as aphids and scale insects, but the range of prey species that various Coccinellidae may attack is much wider. A genus of small black ladybirds, ''Stethorus'', predates non-Sternorrhyncha; they specialise in mites as prey, notably ''Tetranychus'' spider mites. ''Stethorus'' species accordingly are important in biological control on many fruit crops.

Several genera feed on various insects or their eggs; for example, '' Coleomegilla'' species are significant predators of the eggs and larvae of moths such as ''Spodoptera'' and the Plutellidae. Larvae and eggs of ladybirds, either their own or of other species, can also be an important food resource when alternative prey are scarce. The Coccinellidae used to be regarded as purely carnivorous, but they are far more omnivorous than previously thought, both as a family and in individual species; examination of gut contents of apparently specialist predators commonly yield residues of pollen and other plant materials. Most predatory coccinellids include other items in their diets, such as honeydew, pollen, plant sap, nectar, and fungi.

File:Epilachna guttatopustulata01.jpg, '' Henosepilachna guttatopustulata'', a herbivore, feeding on a potato leaf
File:Yellow Shouldered Ladybird (Apolinus lividigaster) with Aphis nerii.jpg, Yellow-shouldered ladybird, '' Apolinus lividigaster'' eating an aphid
File:Harmonia axyridis cannibalism.jpg, ''Harmonia axyridis'' larva cannibalism

Certain species lay extra infertile trophic eggs with the fertile eggs, providing a backup food source for the larvae when they hatch. The ratio of infertile to fertile eggs increases with scarcity of food at the time of egg laying.

Some species in the subfamily Epilachninae are herbivores.

Ecology

The main predators of ladybugs are birds, but they are also the prey of frogs, wasps, spiders, and dragonflies. The bright aposematic colours of many coccinellids discourage potential predators, warning of their toxicity. Their haemolymph contains toxic alkaloids, most commonly polyazamacrolides and polyamines, as well as foul-smelling pyrazines. Some 50 types of alkaloids have been identified in ladybirds. When disturbed, ladybirds further defend themselves with reflex bleeding, exuding droplets of "blood" from their tibio-femoral (knee) joints, effectively presenting predators with a sample of their toxic and bitter body fluid. Changing environmental conditions and invasive species can cause rapid changes in ladybird abundance, as has been documented in the British Isles.

File:Coccinella transversalis 2.jpg, '' Coccinella transversalis'', elytra in the open position
File:Lady beetle taking flight.jpg, Full wings of a ''Harmonia axyridis'' taking flight

Relationship to humans

Biological control

Ladybirds are natural predators of a range of serious pests, such as the European corn borer.

The larva of the vedalia ladybird '' Rodolia cardinalis'' is a specialist predator on a few species of Monophlebidae''. It was introduced to California in 1887 from Australia, to protect citrus trees from cottony cushion scale. The project was markedly successful, making it "a textbook example of the great potential of classical biological control as a tactic for suppressing invasive pests." The vedalia beetle was then used in 29 countries, again with success. This led to many further attempts to use ladybird species against pests. Around 179 ladybird species were deliberately introduced to North America in the 20th century, of which only 18 became established. Further, establishment does not guarantee effective biological control of the target species. Thus, the vedalia beetle's success looks exceptional compared to the Coccinellidae as a whole; reasons for this include its high prey specificity, short generation time, efficient discovery of host patches, and larval development completed on a single host insect.

Some species are voracious specialist predators, making them valuable as agents of biological control, at least when rapid impact is required, as with sudden outbreaks of aphids on crop plants. However, since many prey are transient or seasonal, high specificity and voracity can equally be a disadvantage. Ladybird species vary in specificity; those that are dominant in specific communities are often rather generalist in their diet. Species that are able to multiply quickly in response to aphid outbreaks are mostly generalists, enabling them to survive on other prey while aphids are scarce. The variability of ladybird responses to prey has made finding suitable species for use as biological control agents difficult; out of 155 deliberate introductions meant to control aphids by the year 2000, only one was deemed to be "substantially successful".

Invasive species

''Harmonia axyridis'' (the multicoloured Asian lady beetle or harlequin ladybird) was introduced into North America from Asia in 1979 to control aphids, but it is now the most common species, outcompeting many of the native species. It has become a domestic and agricultural pest in some regions, and gives cause for ecological concern. It has similarly arrived in South Africa, where it has proved variously unwelcome, perhaps most prominently in vine-related crops. The populations in South Africa and South America originated independently from eastern North America. The population in Europe originated partly from eastern North America, and partly from deliberate introduction as a biological control agent in 1982. It has since spread to much of western Europe, reaching the UK in 2004.

''Coccinella septempunctata'', another introduced species in North America, similarly outcompetes and displaces native coccinellids.

Infestations

In North America, coccinellids usually begin to appear indoors in the autumn when they leave their summer feeding sites in fields, forests, and yards and search out places to spend the winter. Typically, when temperatures warm to the mid-60s °F (around 18 °C) in the late afternoon, following a period of cooler weather, they swarm onto or into buildings illuminated by the sun. Swarms of the insects fly to buildings near fields or woods in September through November depending on weather conditions. After an abnormally long period of hot, dry weather in the summer of 1976 in the UK, a marked increase in the aphid population was followed by a "plague" of ladybirds, with many reports of people being bitten as the supply of aphids dwindled.

The herbivorous Mexican bean beetle is an agricultural pest.

The presence of coccinellids in grape harvests can cause ladybird taint in wines produced from the grapes.

In culture

Ladybirds have long been of interest to children. They once had many regional names in English, such as variations on Bishop-Barnaby (Norfolk and Suffolk dialect) – Barnabee, Burnabee, the Bishop-that-burneth, and bishy bishy barnabee. The etymology is unclear, but it may be from St. Barnabas's feast in June, when the insect appears, or a corruption of "Bishop-that-burneth", from the fiery elytra of the beetles. In the 17th century, they were sometimes named "ladycows".

The ladybird was immortalised in the popular children's nursery rhyme ''Ladybird Ladybird'':

This poem has its counterpart in German as ''Marienwürmchen'', collected in ''Des Knaben Wunderhorn'', and set to music by Robert Schumann as Op. 79, No. 13, and a Polish nursery rhyme, "Little Ladybirds' Anthem", of which a part ("fly to the sky, little ladybird, bring me a piece of bread") became a saying.

In Christian areas, they are often associated with the Virgin Mary, and the name that the insect bears in the various languages of Europe corresponds to this. Although historically many European languages referenced Freyja, the fertility goddess of Norse mythology, in the names, the Virgin Mary has now largely supplanted her as the "Lady", so that, for example, ''freyjuhœna'' (Old Norse) and ''Frouehenge'' have been changed into ''Mariehone'' in Danish, ''marihøne'' in Norwegian and ''Marienkäfer'' in German. In Swedish it is ''Maria Nyckelpiga'', Mary the key-maid (who holds the key to heaven). Sometimes, the insect is referred to as belonging directly to God, with Irish ''bóín Dé'', Polish ''boża krówka'', Russian божья коровка 'bozhya korovka'' and Spanish ''Vaquilla de Dios'', all meaning 'God's ittlecow'.

The insects have been used to symbolise Ladybird Books (part of Penguin Group), and the Ladybird range of children's clothing sold by the former high street chain Woolworth's in the UK, while the ladybird street tile is a symbol against senseless violence in the Netherlands, and is often placed on the sites of deadly crimes. They have been adopted as the mascot of Candanchú, a ski resort near Canfranc in the Spanish Pyrenees. The ladybird serves as a long-standing symbol for the Swedish People's Party of Finland. Various lady beetle species have been adopted as US state insects in states such as Delaware, Massachusetts, New Hampshire, New York, North Dakota, Ohio, and Tennessee; some of those designated species, such as ''Coccinella septempunctata'', are introduced rather than native to North America.

References

Sources

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External links

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Beetle families
Articles containing video clips
Biological pest control beetles
Insects used as insect pest control agents
Taxa named by Pierre André Latreille
Insects in culture