The internal classification of the family into tribes and subfamilies is not settled because there are competing systems, none of them clearly correct. In this article, mention of species is grouped according to the food of adults and larvae, an ecological rather than phylogenetic grouping. When subfamilies and tribes are mentioned, it must be understood that these classifications are not universally accepted.

More than 480 species are currently reported to occur in America north of Mexico, just 44 in the British Isles, and 600 in Australia. Most of the 480+ in America north of Mexico are considered to be native, and others to be adventive (having arrived from somewhere else and established feral populations). Among the adventive species, some were introduced (introduced deliberately), and others are immigrants (having arrived by any means except deliberate introduction).

Ladybird adults are oval, range in length from about 1 mm to over 10 mm depending upon species, and have wings. Females on average are larger than males. Adults of some species are brightly colored. Their mandibles are used for chewing. Adult ladybirds are able to reflex-bleed from the tibio-femoral articulations (leg joints). The blood (hemolymph) is repellent by having a repulsive smell as well as containing (in some species) various alkaloid toxins (adaline, coccinelline, exochomine, hippodamine, etc.). The hemolymph is yellow and its repellency and toxicity are believed to be a defense mechanism against predators. Some people have claimed that the bright (red on black, or black on red) colors of some adult ladybirds are aposematic, which is to say that the colors warn would-be predators that the beetles are distasteful or toxic.

The immature stages (eggs, larvae, and pupae) also contain the toxins that their adults have. Toxins are said to be produced by dorsal glands in the larvae. Eggs are elongate-ovoidal, and in just a few species are protected by secretions of the adult female. Cannibalism of eggs, larvae and pupae is common, especially when prey is scarce. Larvae are mobile, and in some species (for example of Scymnus and Cryptolaemus) are protected by waxy secretions. Pupae are unprotected by a cocoon (some other beetles pupate in a cocoon) but larvae may wander some distance from feeding sites (where they may be at risk from cannibalism) before pupating.

Ladybird eggs are laid in clusters by at least most aphid-eating species and singly by at least most scale-insect-eating species. Eggs produce larvae that undergo four instars before pupating, metamorphosing, and giving rise to adults. One scale-eating ladybird is reported to have only three instars. Ladybirds may have one or, more typical of warmer climates, several generations each year, and reproduction is slowed or halted by cooler winter weather, when adults may hibernate. In hot, dry climates, ladybirds may aestivate (become inactive) during the hottest months.

Ladybirds that feed on aphids develop faster, age faster, move faster, typically are larger, and lay their eggs in clusters. Those that feed on scale insects develop more slowly, live longer, move more slowly, typically are smaller, and lay their eggs singly.

Ladybird larvae and adults may supplement their normal prey in times of scarcity with other types of food. They consume flower nectar, water and honeydew – the sugary excretion of piercing-sucking insects such as aphids and whiteflies – or pollen. Many plant species also contain organelles in locations on the plant other than the flower – termed extrafloral nectaries – that produce a nutrient-laden secretion. While it was first thought that extrafloral nectaries were used by the plant for excretion, it is well substantiated that most plants actually use the extrafloral nectaries to attract predators and parasites for protection from their herbivores. Over 2,000 species of plants in 64 families have extrafloral nectaries. Extrafloral nectaries may be located on leaf laminae, petioles, rachids, bracts, stipules, pedicels, fruit, etc. Ladybirds often use the secretions from extrafloral nectaries in their diet and are just some of the many beneficial insects that use extrafloral nectary secretions.

Most species of ladybirds are considered beneficial because they are predators of Hemiptera: Sternorrhyncha or Acarina, many of which are considered to be pests. These predatory ladybirds contribute to the regulation of populations of their prey, and in some situations contribute a high level of regulation. When ladybirds naturally contribute a high level of control of pests, or in combination with other predators and/or parasitoids and diseases contribute a high level of population regulation of pests, people may benefit. That is to say that gardeners, growers and farmers may benefit, at no cost, because they have no or negligible pest problems.

Sometimes, gardeners mistake the ladybird larvae for pests and spray chemical pesticides that kill them (this is much less of a problem with growers and farmers because they have more experience). The result is increased problems from real pests. The answer is a constant educational effort to inform people about ladybirds and what their larvae look like. This effort cannot end, because people knowing nothing about ladybird life cycles are born each minute.

One type of biological control is thus called manipulative biological control (of which a subset is conservation biological control). The objectives are simply to capitalize on the ladybirds (or other beneficial organisms) that already are present, to make conditions as favorable as possible for them (manipulation), and especially to avoid spraying chemicals (insecticides, fungicides, or herbicides) that will harm them (conservation).

A second type of biological control is augmentative biological control. This begins with the recognition that ladybirds in a given pest situation are present but too few to do the job required, and buying more from a commercial producer to release to augment those already present. A risk is that if adult ladybirds are released, many of them may fly away. But, if ladybird larvae are released, they have the option of eating the pest with which they are presented, or starving – they cannot fly away. Obviously, this requires matching the pest to a purchased ladybird species that will eat that pest (see above for species options). The rub here is that the number of purchased ladybirds needed for a given pest situation may not have been worked out in detail – it demands a huge amount of practical experience to tie down the details for at least hundreds of situations. Documentation of this experience is progressing very slowly.

A third type of biological control is classical or inoculative biological control. Here, some individuals of a ladybird (or other) species that is not already present are released in the hope that they will establish a population and eventually control the pest that is of concern. Classical biological control typically applies to a situation in which a new pest has invaded, and researchers (from a university, or a national or state department of agriculture) import and release a ladybird (or other kind of organism) that is believed to control the pest elsewhere. Typically, the imported ladybird (or other organism) becomes established or does not become established; if it becomes established, it may or may not control the pest in this new situation. Typically, the foregoing things are done under the name of “research,” and either are cost-free to gardeners, growers and farmers (especially if done by state or federal departments of agriculture) or, if done by university researchers, then gardeners, growers and farmers are asked to contribute toward a grant that will pay for the cost of importation and research on the biological control agent (but subsequently, after it has become established, there are no further costs). The archetypical example is control of cottonycushion scale of citrus by the introduced ladybird Rodolia cardinalis. Although chemical pesticides of the time were failing to control it, and although it threatened to ruin California’s citrus industry, nobody was willing to invest funds in biological control research. Nevertheless, biological control research was “bootlegged” onto other operations by dedicated researchers, was astoundingly successful, and saved California’s (and later Florida’s) citrus industry from ruin: there was no subsequent need to use chemicals against this pest, thus saving billions of dollars as against a trivial expenditure (about $1,500 at the time, for foreign travel).

Glasshouses (greenhouses) provide a habitat for plants and pests and biological control agents that differs from outdoor habitats. Typically, culture begins with initiation of a crop of plants that has no pests (or seems to have none). But then pests somehow show up, and there are no ladybirds (or other organisms) to control them. The situation is very much like that of classical biological control, and ladybirds (and/or other beneficial organisms) released into the greenhouses may control the pests and eliminate need to use chemical pesticides. Here, the question is not about funding new research into a new pest, but into buying the right numbers of ladybirds (or other organisms) of the appropriate species to control a pest that has already been researched. For many such situations, ladybirds (or other organisms) can be purchased from commercial supply houses to control the pest(s).

The following is a partial species list of commercially available ladybirds posted on the California Department of Food and Agriculture’s website, which can be accessed to provide information about commercial suppliers in Canada, Mexico and the USA in 1997 (it is not up-to-date). The URL (http://www.cdpr.ca.gov/docs/ipminov/bensuppl.htm) still works.

Coleomegilla maculata – a predator of aphids.

Cryptolaemus montrouzieri – a predator of mealybugs.

Delphastus pusillus – a predator of whiteflies.

Harmonia axyridis – a predator of aphids.

Hippodamia convergens – a predator of aphids. Some suppliers do not rear the beetles but collect overwintering adults from the mountains of eastern California; these overwintering adult beetles (i) may be heavily parasitized and many may die, and (ii) may be programmed at the end of the winter to end the hibernation by flying west, which may do you no good if they all take to flight and leave your property.

Rhyzobius lophanthae – a predator of scale insects.

Rhyzobius ventralis – this name is listed in error, it should be called Rhyzobius forestieri (Mulsant).

Stethorus picipes – a predator of tetranychid mites; this name is listed in error, it should be called Stethorus punctum picipes Casey, a subspecies of Stethorus punctum (LeConte).

Stethorus punctillum – a predator of tetranychid mites.

Commercial suppliers of biocontrol agents in Australia are listed by the Association of Beneficial Arthropod Manufacturers (ABA: http://www.gc.goodbugs.org.au), and some of these suppliers sell ladybirds. Commercial suppliers of biocontrol agents in Europe (and some other countries around the world) are listed by the International Biocontrol Manufacturers Association (IBMA: http://www.ibma.ch), and some of the listed companies sell ladybirds. Commercial suppliers belonging to the Association of Natural Biocontrol Producers, a North American Organization, are listed (ANBP http://www.anbp.org). By examining the individual sites of these companies, you may determine what ladybird species are available and, from the websites of some of these companies, some of the characteristics of the species available.

There is yet no website listing insect cultures available worldwide for purchase, with a list of suppliers for each species. Insect Production Services, Natural Resources Canada, is beginning to compile such a list (http://www.insect.gflc.cfs.nrcan.gc.ca).

However, just because a biocontrol agent such as a ladybird species (or subspecies), is available somewhere in the world for purchase, does not necessarily mean you will be able to obtain it. Your own national (and perhaps provincial or state) department of agriculture (or some other government agency) may regulate importations. It is most probable that you will only be able to import species (and subspecies) that already exist in your area. For example, all shipments of living insects into Florida are required to have permits from the Florida Department of Agriculture and Consumer Services, Division of Plant Industry; in general, a permit will be supplied for importation of species (and subspecies) that already occur in Florida. It is the vendors who are required to obtain the permits for commercial shipments. Furthermore, no reputable producer is likely to ship living ladybirds to you unless there is a rapid commercial shipper. Stated policies of some international shippers (e.g., Federal Express, DHL, UPS) say that they will not accept consignments of living animals (including insects) for reasons that they do not explain. The lesson is that you should buy from a local supplier wherever possible.

Despite all the difficulties in purchase and shipment, some biocontrol producers can provide you with a good product rapidly. Please see the website of the Belgian producer Biobest (http://www.Biobest.be), which also has websites in other countries (at least Canada, France, Greece, and Spain) as an example of how it can work. That company provides you an online description of the product and what it can do.

Four ladybird species (Coleomegilla maculata, Cryptolaemus montrouzieri, Harmonia axyridis, and Hippodamia convergens) have been reared on purely artificial diets, thus promising to reduce labor costs and thus the price of commercially available ladybirds. Diets for others may now be available or under development.

The great success of the imported Rodolia cardinalis in controlling cottonycushion scale in California and then in various countries around the world led to great enthusiasm among growers to attempt importation of additional ladybirds to control a long list of pests of plants. Many of these additional ladybirds failed to establish where they were introduced. Others became established but did not provide the required level of control. Relatively few achieved the required level of control. One of the reasons for success of R. cardinalis was its high level of specialization to cottonycushion scale – it would control that pest effectively, but no others.

Growers of many crops encounter pest aphids. Ladybirds that prey on aphids are widely distributed, and native ladybirds are often recruited to aphid infestations on crop plants in North America and elsewhere. Perhaps it was a sense of lack of effectiveness of native ladybirds in rapid and complete control of aphid infestations that led to attempts to import additional aphid-feeding ladybird species into North America. At all events, considerable effort was made by USDA entomologists (in collaboration with state and university entomologists) to import the Eurasian Coccinella septempunctata and the Asian Harmonia axyridis to eat more aphids than were consumed by native ladybirds. Whether those efforts succeeded or whether those two ladybird species arrived as immigrants is unclear, but eventually both species became established and spread widely. They proved to be more successful than native ladybirds at controlling aphids in general, and their populations grew and spread. Perhaps if this had happened in the 19th century the success would have been welcomed. But, by the late twentieth century, it was their side-effects that received publicity – there is some evidence that in some places native ladybird populations have declined because of the efficiency of the introduced ladybirds in killing aphids and thus denying food to the native ladybirds. It is undeniable that adult H. axyridis may hibernate in some places (loosely constructed houses, railway electrical boxes, etc.) where they are not welcome. It matters little that houses and railway electrical boxes should and could have simple physical screens to exclude insects (building codes in the southern U.S.A. require screening of houses against mosquitoes) because the public has become incensed against H. axyridis. The era of importation of generalist biological control agents has ended (even, for example, those that feed on many aphid species but no other prey may no longer be welcome), and only specialists may in future be permitted.