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Asian lady beetle is an abundant, introduced species that has largely displaced most larger-sized species of native lady beetles throughout North America. Adults of this species are circular or slightly oblong lady beetles, 5 mm to 8 mm in length. They are extremely variable in overall color, from nearly black to light tan. The number and arrangement of spots on the elytra (wing covers) also vary, from one pair to nine pairs. Spots may even be completely absent. One fairly consistent characteristic is the presence of a dark “W” (or “M”) on the pronotum (top of thorax) formed by a series of dark spots on a pale background, but this may be obscured on dark specimens. The variable coloration of adults and wide distribution has led to a great many common names, including variegated Asian lady beetle, multicolored Asian lady beetle, harlequin beetle, pumpkin ladybird and many more.
Larvae have been described as “alligator shaped” and may reach 10 mm in length. They bear a distinct array of spines along the sides of the body. They are typically dark brown to black with a yellowish orange to pinkish series of markings on either side of the midline of the abdomen. Larvae are also somewhat variable in appearance, but less so than adults.
Asian lady beetle is one of approximately 75 species within the lady beetle family Coccinellidae that have been documented in Louisiana. About 6,000 species are described worldwide. The vast majority of large lady beetles encountered in Louisiana recently are Asian lady beetles.
Both adults and larvae are voracious predators of aphids and are not picky about aphid prey species. Thus, they may be found on a variety of aphid infested plants. Adult females lay eggs near aphid prey infestations and larvae hatch within a few days and begin feeding. Larvae go through four instars (growth stages), molting between each stage. When mature, the larva attaches to any elevated surface and molts into the pupal stage, during which it transforms into an adult. Total life span varies with climate, with two generations per year in northern areas and four in southern states, including Louisiana, where adults may be present virtually year-round.
The Asian lady beetle was introduced intentionally from its native east Asia to the U.S. several times during the 20th century as a biological control agent for aphids but apparently failed to establish persistent populations. During 1988, adults were recovered in large numbers by Vernon Brou near Abita Springs, Louisiana. The source of the introduction was unknown but presumably was the result of accidental introduction at one of the major regional ports on the Gulf, either New Orleans or Mobile, Alabama. The species spread rapidly to the remainder of the U.S. and southern Canada during the following years. Asian lady beetle has also been introduced to Europe, South America and other parts of the world as a result of human activity. It is a major cause of the decline of many native lady beetles that compete for the same resources. Adults of Asian lady beetle and several other lady beetle species are nuisance pests to homeowners and businesses as a result of their tendency to aggregate in large numbers inside structures during fall and early winter as an overwintering behavior. Contamination of produce has also been reported. The species never reproduces inside structures. They do secrete a malodorous, irritating defensive fluid when disturbed. Adults may occasionally bite exposed skin, as do many other species of lady beetles, but these bites are superficial and not medically significant. Social media reports that they are a threat to pets are greatly exaggerated. A widely distributed social media rumor suggests that Asian lady beetles are a threat to domestic dogs and will attach to the roof of the pet’s mouth. This is based on an apparently isolated case where a dog came in contact with a large aggregation of lady beetles and ingested a large number of them, prompting a trip to the vet. Another widespread misconception holds that this species is not a true lady beetle. It is in fact a member of the same family (Coccinellidae) as all other lady beetles, so it is a true lady beetle, albeit a less well-liked member of the family.
Many Asian lady beetles are infected with members of a species complex of fungal external parasites in the genus Hesperomyces (Laboulbeniales). These are sometimes visible on superficial inspection of the beetles, but are easily visible under moderate magnification. The Asian lady beetle does not seem to suffer ill effects from the fungal infestations, which can be quite heavy on some individuals. Some studies have suggested that the fungus plays a role in the decline of other lady beetle species. This is an area of active investigation.
In cases where a home or business is infested with overwintering beetles, physical removal (e.g., vacuuming) and sealing points of entry are the best options. No other control methods are recommended.
Brown, P.M.J., and H.E. Roy. 2018. Native ladybird decline caused by the invasive harlequin ladybird Harmonia axyridis: evidence from a long-term field study. Insect Conservation and Diversity 11: 230-239.
Ceryngier, P., and K. Twardowska. 2013. Harmonia axyridis (Coleoptera: Coccinellidae) as a host of the parasitic fungus Hesperomyces virescens (Ascomycota: Laboulbeniales, Laboulbeniaceae): A case report and short review. European Journal of Entomology 110: 549-557.
Chapin, J.B., and V.A. Brou. 1991. Harmonia axyridis (Pallas) the third species of the genus to be found in the United States (Coleoptera: Coccinellidae). Proceedings of the Entomological Society of Washington 93: 630-635.
Roy, H., and E. Wajnberg. 2008. From biological control to invasion: the ladybird Harmonia axyridis as a model organism. Biocontrol 53: 1-4.
Contact Us: For advice about pest identification or diagnosis, contact the LSU AgCenter Department of Entomology.
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Adult Asian lady beetle. Photo by Chris Carlton
Variation in adult Asian lady beetle external appearance. Photo by Bill Ree, Texas A&M University, Bugwood.org
Asian lady beetle mature larva. Photo by David Cappaert, Bugwood.org
