Rodolia cardinalisvedalia

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Geographic Range

Although native to Australia, Rodolia cardinalis flourishes today throughout Australia, the United States, and Europe in areas where citrus is grown. (Borror, et al., 1981; Weeden, et al., 2004)

Habitat

Rodolia cardinalis are specialists, feeding on Icerya purchasi which in turn specialize on citrus trees. For this reason, Rodolia cardinalis live in citrus orchards and nearby hills and scrubland in areas where Icerya purchasi are also found. In addition to citrus, cottony cussion scales are found on Acacia, boxwood, citrus, magnolia, Nandina, olive, Pittosporum, and rose plants, which therefor additionally provide habitat for the vedalia beetle. (Buchsbaum, et al., 1987; Weeden, et al., 2004)

Physical Description

This species of ladybeetle, like others, has a very distinctive shape. The body is broadly oval to nearly spherical, and is strongly convex dorsally and nearly flat ventrally. The head has short antennae and is partly or completely concealed by the pronotum. Females are very red in color, while males are more black although fine body hairs often obscure the color pattern and give a decidedly grey appearance. Eggs are bright red. Mature larvae are pinkish with black markings and often have a blueish tinge. (Borror and White, 1970; Essig, 1926)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • female more colorful

Reproduction

Rodolia cardinalis reproduces sexually. In warm climates there are several generations each year. The bright red eggs are laid on the egg sac of the cottony cushion scale in small, closely packed masses of one or two dozen. Upon hatching, the small pinkish larvae immediately enter the sac and feed on the scale eggs. These larvae are usually found in aphid colonies. (Borror and White, 1970; Milne and Milne, 1980; Waldbauer, 2000)

  • Range eggs per season
    150 to 190

Behavior

Vedalia beetles are commonly seen on plants and often overwinter as adults in large swarms under fallen leaves or bark. Wintering aggregations are collected by the bushel from high California hills and sold to citrus growers. In early spring the beetles are liberated in orchards; others make their own way down into valleys where citrus is grown. During the dry season, new generations return to a high, cool refuge. The success of the insect is due to the rapidity of development, hardiness, and their greedy appetites. (Borror, et al., 1981; Buchsbaum, et al., 1987; Milne and Milne, 1980)

Food Habits

Both adults and larvae are voracious predators. Homopteran pests including aphids, scale insects, mealy bugs, and mites are food for R. cardinalis. Adults and larvae search the foliage of bushes and trees in search of prey. (Buchsbaum, et al., 1987; Burton, 1968)

  • Animal Foods
  • insects

Economic Importance for Humans: Positive

Rodolia cardinalis is used commercially to combat scale insects injurious to citrus orchards, specifically Icerya purchasi, the cottony cushion scale. Orchard owners use this form of Integrated Pest Management(IPM)--use of a variety of strategies for the control of insect pests, including cultural, chemical, and biological controls while restricting and altering the use of pesticides--to control a pest population always present. The natural predator of Icerya Purchasi is used (R.cardinalis) instead of pesticides and other such materials. Aggregations of the beetle are collected by the bushel and sold to citrus growers. When imported from Australia to California in the 19th century,they brought with them no natural predators, making them an ideal animal to use for pest management. (Bellamy and Evans, 1996; Burton, 1968)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

In its North American habitat, the vedalia beetle has no natural predators and so can outcompete native ladybugs which also offer important pest control benefits.

Conservation Status

Rodolia cardinalis is extremely sensitive to some insecticides such as Baythroid, commonly used on citrus crops. Global populations are strong however, and require no special conservation status. (Weeden, et al., 2004)

Other Comments

In the Middle Ages, certain species of coccinellid beetles were dedicated to the Virgin Mary and named "beetles of Our Lady." As time progressed ladybird beetles, ladybirds, or ladybugs became popular names with English-speaking children.

Rodolia cardinalis is native to Australia. However, in 1868 Icerya purchasi, a cottony cushion scale (and also from Australia), was introduced to California accidentally as a serious pest of citrus in California. In 1888-1889 R. cardinalis was intentionally introduced to California because it was a natural predator of the scale. In less than 2 years the scale was under complete control and R. cardinalis adapted and flourished in the new environment. Its distribution now includes Australia, the United States, and Europe. (Bellamy and Evans, 1996; Borror, et al., 1981; Weeden, et al., 2004)

Contributors

Sara Diamond (editor), Animal Diversity Web.

Heather Martin (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

year-round breeding

breeding takes place throughout the year

References

Bellamy, C., A. Evans. 1996. An Inordinate Fondness for Beetles. New York: Henry Holt and Company, Inc..

Borror, D., D. Long, C. Triplehorn. 1981. An Introduction to the Study of Insects. Philadelphia: Saunders College Publishing.

Borror, D., R. White. 1970. A Field Guide to Insects. Boston: Houghton Mifflin Company.

Buchsbaum, R., M. Buchsbaum, J. Pearse, V. Pearse. 1987. Animals Without Backbones. Chicago: The University of Chicago Press.

Burton, J. 1968. The Oxford Book of Insects. Oxford: Oxford University Press.

Essig, E. 1926. Insects of North America. New York: The Macmillan Company.

Milne, L., M. Milne. 1980. The Audobon Society Field Guide to NOrth Americna Insects and Spiders. New York: Alfred A. Knopf.

Waldbauer, G. 2000. Millions of Monarchs, Bunches of Beetles. Cambridge, Massachusetts: Harvard University Press.

Weeden, , Shelton, Li, Hoffman. 2004. "Cornell University, Biological Control" (On-line). Accessed April 07, 2005 at http://www.nysaes.cornell.edu/ent/biocontrol/predators/rodolia_cardinalis.html.