Early stages of predatory beetles. From left: larva of carabid ground beetle, centre: two cannibal larval harlequin ladybirds eating another. Right: pupa of 7-spot ladybird.
Role of predatory land beetles in gardens
Ground beetles, rove beetles, ladybirds and their larval stages prey on a wide range of insects and other invertebrate animals in the soil and on plants. Some of these prey items, such as aphids, are significant pests of garden plants. A ladybird, Cryptolaemus montrouzeri, can be purchased to control mealybugs in greenhouses. A rove beetle Atheta coriaria, is similarly available for the control of fungus gnat/sciarid fly larvae.
Since the arrival of the harlequin ladybird, some native ladybird species seem to have declined in numbers
. This may be the result of competition for food resources, or through predation by the harlequin ladybird of native ladybird species. The two-spot ladybird is the species that has shown the greatest reduction in abundance.
Other sources of information
Forsythe, T. G. (2000) Naturalists' Handbooks 8 Ground Beetles. Richmond Publishing
Lott, D. A. (2009). Handbooks for the identification of British insects, vol. 12, part 5 The Staphylinidae (rove beetles) of Britain and Ireland. Part 5: Scaphidiinae, Piestinae, Oxytelinae. Royal Entomological Society
Lott, D. A. and Anderson, R. (2011). Handbooks for the identification of British insects, vol. 12, part 7 The Staphylinidae (rove beetles) of Britain and Ireland. Parts 7 & 8: Oxyporinae, Steninae, Euaesthetinae, Pseudopsinae, Paederinae, Staphylininae. Royal Entomological Society.
Luff, M. L. (2007) Handbooks for the Identification of British Insects Vol 4 part 2 The Carabidae (ground beetles) of Britain and Ireland. Royal Entomological Society
Majerus, M. E. N. (1994) Ladybirds Collins New Naturalist series no. 81. Harper Collins
Roy, H., Brown, P., Frost, A. & Poland, R. (2011) Ladybirds (Coccinellidae) of Britain and Ireland. Field Studies Council
Roy, H., Brown, P., Comont, R., Frost, A., Poland, R. & Sloggett, J. (2013) Naturalists' Handbooks 10 Ladybirds. Pelagic Publishing