Wild species 2010: chapter 14

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Insects: Lady beetles

Coccinellidae - Family of insects in the order Coleoptera. These species are generally brightly coloured, often red with black markings, and they mostly feed on aphids.

Quick facts

• There are about 6000 species of lady beetles in the world, of which 166 have been found in Canada.
• When excluding species ranked as Extinct, Extirpated, Undetermined, Not Assessed, Exotic or Accidental, the majority (84%) of lady beetles in Canada have Canada General Status Ranks (Canada ranks) of Secure, while 16% have Canada ranks of Sensitive.
• Lady beetles belong to the family Coccinellidae, one subfamily, Coccinellinae, are the bright red and black species most people recognize. Most species are small black or brown beetles and rarely noticed.
• The bright red and black pattern of many species is a warning that they contain alkaloids and therefore taste bad to predators.
• Seven species of lady beetles are Exotic in Canada.
• Most lady beetles are predatory, feeding on aphids, hoppers, scale insects, mites and other soft-bodied plant feeders. Many of these are important in reducing populations of plant pests. A few species feed on moulds, pollen and plants.

Background

For insects, lady beetles (family Coccinellidae) have a very good reputation. The bright red and black species are readily recognized and perceived to be beneficial to humans and a popular subject for rhymes and song. Biocontrol programs often use lady beetles because adults and larvae of many species eat plant feeding insects, such as aphids and scale insects. Many are habitat generalists, congregating where aphids are plentiful, including gardens and agricultural fields where the bright colours make them easy to see. Once people realize that shape is more important than counting the number of spots, most species are relatively easy to identify. The widespread interest and ability to identify most species make them a good choice to be ranked as part of the general status program.

Most people recognize as lady beetles the ones that are relatively large (>5 mm), brightly coloured (red, yellow or orange) with black spots or stripes.

These are the ones most people think of when lady beetles (or Ladybugs or Ladybirds) are mentioned. About one third of the Canadian species fit this description. Bright colours are associated with bad taste. Most of the brightly coloured lady beetles have high concentrations of alkaloids that deter predators. The majority of species are more difficult to recognize as lady beetles, being smaller and usually lacking bright colours. They can be recognized by the rounded shape, head mostly hidden from above, clubbed antennae and a bilobed second tarsus.

In southern Canada, where most people live and see lady beetles, most of the individuals they see are of non-native species. Many attempts were made to introduce non-native lady beetles to assist with control of crop pests such as aphids. These introductions did not result in established populations. However unintentional introductions happened. Since the 1980s, non-native species are the ones that are most frequently seen in settled regions of southern Canada. The Seven-spotted Lady Beetle (Coccinella septempunctata) from Europe has been widespread since the 1980s. Since the mid-1990s, the Multi-coloured Asian Lady Beetle (Harmonia axyridis) has spread across southern Canada and now is the most abundant lady beetle in many locations. People notice this species more than other lady beetles because they congregate in buildings, including houses, barns and office buildings to spend the winter. It is also the species most often misidentified because of the variation in colour, from black to red to orange, and the variation in the number of spots, from none to more than 20. If only spots are counted, this species will usually be misidentified. More reliable is the relatively large size and the dark “M” on the section behind the head.

Coinciding with the arrival of non-native species, such as the Seven-spotted and Multi-coloured Asian Lady Beetles, has been the decline in populations of native species, such as the Nine-spotted Lady Beetle (Coccinella novemnotata) and the Transverse Lady Beetle (Coccinella transversoguttata). Both species were widespread in eastern Canada in a variety of habitats, including suburban and agricultural landscapes, up to the 1960s. The Nine-spotted Lady Beetle has not been seen in Ontario and Quebec since the 1980s and reports in western Canada have slowed to a trickle. The relative importance of factors such as competition with non-native species, disease, habitat change, and changes in agriculture are being studied.
Adult female lady beetles lay small clumps of eggs on plants where food will be available for the larvae. Larva often eats other eggs in the clump in which it was laid. If there are few aphids, this allows a larva to survive until aphid numbers can increase, or until the larva can walk to a nearby plant. Larvae are active predators of soft-bodied plant feeding insects (a few feed on moulds or plant leaves). They are elongate with three pairs of spindly legs near the head. After feeding for two to three weeks, they form a pupa, often on the plant where they were feeding. In the pupa, a radical transformation occurs, changing from the larva to the round adult with the hard wing covers that we are familiar with. A few days or weeks later, the adult emerges. Most species overwinter as adults, emerging in the spring to mate and lay eggs.

Status of knowledge

Due to their bright colours, association with habitats near human settlements and role in biocontrol of agricultural pests, some lady beetle species have been relatively well studied. Much of the work focuses on lady beetles as predators, their parasites, development and genetics. Almost all of the work has been done in agricultural systems. Little work has been done on habitat preferences away from agricultural landscapes and therefore geographic distributions and food preferences for species not found in agricultural systems are poorly known. Many species of lady beetles in natural ecosystems then remains relatively unknown.

Richness and diversity in Canada

A total of 166 of the approximately 475 species in North America are known from Canada. Fifty six of the Canadian lady beetles belong to the subfamily Coccinellinae, which are colourful beetles that are active during the day and common in human disturbed habitats. About 100 species of small, round, brown Scymninae make it the most diverse subfamily. Four other subfamilies are represented by one to eight species, Sticholotidinae, Chilcorinae, Coccidulinae and Epilachninae.

Lady beetles are found in every province and territory (figure 14). They are most diverse in British Columbia, Alberta, Ontario and Quebec with more than 70 species in each of these provinces.

Species spotlight - Seven-spotted Lady Beetle

The Seven-spotted Lady Beetle (Coccinella septempunctata) is the familiar red lady beetle with black spots found in most of southern Canada. Wherever aphids are abundant, there are bound to be some seven-spots. However 50 years ago, it did not exist in Canada.

The role lady beetles play in controlling plant pests, particularly aphids, is well known. Therefore, Seven-spotted Lady Beetles were introduced to Canada for biocontrol many times. However it appears that none of these intentional introductions resulted in an established population. In the mid-1970s, an unintentional introduction established a small population that rapidly grew, so that by the mid-1980s, from the east coast to Ontario, the seven-spotted was the common lady beetle in agricultural areas. By 1990, they were in British Columbia.

The largest populations are in human disturbed habitats such as city parks, agricultural fields and roadsides. After overwintering as adults, eggs are laid. The larvae feed on aphids and within a few weeks become adults. These adults mate and females lay eggs on plants infested with aphids. This generation becomes adults in the summer, some lay more eggs and others overwinter. There is no strong preference for particular species of plants or aphids.

Lady beetle populations have been best studied in agricultural fields. In Manitoba, populations of some native species, such as the Transverse Lady Beetle, declined after the arrival of the seven-spot. What has caused the declines in some species and why other species thrive in the same human modified habits is not clear.

Species spotlight - Nine-spotted Lady Beetle

Sixty years ago, one of the common lady beetles around family farms across southern Canada was the Nine-spotted (Coccinella novemnotata). Today, they still persist in southern Alberta and British Columbia, but are more likely to be found in natural vegetation along the edges of sand dunes than in agricultural fields. In southern Ontario and Quebec, they have not been seen for about 25 years. It is very likely they are extirpated in eastern Canada.

Recent reports of nine-spots often prove to be another species. Variable lady beetles, such as the Multi-coloured Asian, can have nine spots. In the west, nine-spots may lack spots. It is important to look for the dark strip in the middle of the back, the overall shape and size and the pattern behind the head to confirm the identification.

Both larvae and adults feed on aphids and other soft-bodied insects that feed on plants. Females search for plants that harbour concentrations of aphids and lay eggs. Like many lady beetles, nine-spots are generalists and will lay eggs on many species of plants, including many crops. The relative roles of competition with non-native species, disease, and changes in land use in the decline of this species are not clear. The Nine-spotted Lady Beetle has a general status Canada rank of Sensitive.

Results of general status assessment

The majority of Canada’s 166 species of lady beetles have Canada ranks of Secure (77 species, 46%, figure 14 and table 21). However, 9% have Canada ranks of Sensitive (15 species).

A total of 66 species (40%) have a Canada rank of Undetermined and one species (1%) have a Canada rank of Not Assessed. There are seven species (4%) of lady beetles ranked as Exotic that are established in Canada.

Threats to Canadian lady beetles

Most attention has been focused on the coincidence of the decline of native species (e.g. Nine-spotted Lady Beetle and Transverse Lady Beetle) with the arrival and spread of non-native species such as the Seven-spotted Lady Beetle than other factors in the decline of several lady beetles. The relative importance of competition with non-native species compared with habitat and land use changes in the decline are not clear.

Conclusion

Although some studies have been done on lady beetles, much remains to be learned about the range and status of lady beetles in Canada. The potential effects of non-native species on changes in the geographic ranges of native species have led to increased attention to this group in the past 20 years.

Further information

Acorn, J. H. 2007. Ladybugs of Alberta, finding the spots and connecting the dots. University of Alberta Press, Edmonton: 169 pp.

Brown, W. J. 1962. A revision of the forms of Coccinella L., occurring in America north of Mexico (Coleoptera: Coccinellidae). The Canadian Entomologist 94: 785-808.

Dobzhansky, T. 1935. A list of Coccinellidae of British Columbia. Journal of the New York Entomological Society 43: 331-336.

Giorgi, A. and Vandenberg, N. 2009. Coccinellidae. Lady beetles, Ladybird beetles, Ladybugs. In The Tree of Life Web Project. (Accessed March 30, 2010).

Gordon, R. D. 1985. The Coccinellidae (Coleoptera) of America north of Mexico. Journal of the New York Entomological Society 93: 1-912.

Gordon, R. D. and Vandenberg, N. 1991. Field guide to recently introduced species of Coccinellidae (Coleoptera) in North America, with revised key to North America genera of Coccinellini. Proceedings of the Entomological Society of Washington 93: 845-864.

Larochelle, A. 1979. Les Coleoptères Coccinellidae du Québec. Cordulia Supplement 10: 1-111.

Lost Ladybug Project. 2010. (Accessed March 30, 2010).

Majerus, M. E. N. 1994. Ladybirds. The new naturalist. HarperCollins, London: 367 pp.

Majka, C. G. and McCorquodale, D. B. 2006. The Coccinellidae of the Maritime Provinces of Canada: new records, biogeographic notes and conservation concerns. Zootaxa 115: 49-68.

Marshall, S. 2000. Lady beetles of Ontario. Coccinellidae-Lady beetles (Accessed March 30, 2010).

Vandenburg, N. J. 2002. Coccinellidae Latreille 807. In American beetles volume 2, Polyphaga: Scarabaeoidea through Curculionoidea (R. H. Arnett, M. C.

Thomas, P. E. Skelley and J. H. Frank, editors). CRC Press, Boca Raton: 371-389.

Watson, W. Y. 1979. North American distribution of Coccinella U. undecimpunctata L. (Coleoptera: Coccinellidae). The Coleopterists Bulletin 33: 85-86.

Wise, I. L., Turnock, W. J. and Roughley, R. E. 2001. New records of coccinellid species for the province of Manitoba. Proceedings of the Entomological Society of Manitoba. 57: 5-10.

References

Belicek, J. 1976. Coccinellidae of western Canada and Alaska with analyses of the transmontane zoogeographic relationships between the fauna of British Columbia and Alberta (Insecta: Coleoptera: Coccinellidae). Quaestiones Entomologicae 12: 283-409.

Harmon, J. P., Stephen, E. and Losey, J. 2007. The decline of native coccinellids (Coleoptera: Coccinellidae) in the United States and Canada. Journal of Insect Conservation 11: 85-94.

Headstrom, R. 1977. The beetles of America. A. S. Barnes and Co. Inc., Cranbury: 488 pp.

Lucas, É., Vincent, C., Labrie, G., Chouinard, G., Fournier, F., Pelletier, F., Bostanian, N. J., Coderre, D., Mignault, M.-P. and Lafountaine, P. 2007. The multicolored Asian Ladybeetle Harmonia axyridis (Coleoptera: Coccinellidae) in Quebec agroecosystems ten years after its arrival. European Journal of Entomology 104: 737-743.

Turnock, W. J., Wise, I. L. and Matheson, F. O. 2003. Abundance of some native coccinellines (Coleoptera: Coccinellidae) before and after the appearance of Coccinella septempunctata. Canadian Entomologist 135: 391-404.