List of prey
Coccinellids are best known as predators of Sternorrhyncha such as aphids and scale insects, but the range of prey species that various Coccinellidae may attack is much wider. A genus of small black ladybirds, Stethorus, presents one example of predation on non-Sternorrhyncha; they specialise in mites as prey, notably Tetranychus spider mites. Stethorus species accordingly are important in certain examples of biological control. They are natural predators of a range of serious pests, such as the European corn borer, a moth that costs US agriculture industry more than $1 billion annually in crop losses and population control.
Various larger species of Coccinellidae attack caterpillars and other beetle larvae. Several genera feed on various insects or their eggs; for example, Coleomegilla species are significant predators of the eggs and larvae of moths such as species of Spodoptera and the Plutellidae. Larvae and eggs of ladybirds, either their own or of other species, can also be an important cannibalistic food resource when alternative prey are scarce. As a family, the Coccinellidae used to be regarded as purely carnivorous, but they are now known to be far more omnivorous than previously thought, both as a family and in individual species; examination of gut contents of apparently specialist predators commonly yield residues of pollen and other plant materials. Besides the prey they favour, most predatory coccinellids include other items in their diets, including honeydew, pollen, plant sap, nectar, and various fungi. The significance of such nonprey items in their diets is still under investigation and discussion.
In Florida, adults and larvae of 75 species feed on scale insects (in the broad sense, see below), and only 13 feed primarily on aphids. As pointed out by Dixon (2000), there are typical differences in behavior between these trophic groups. Those 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.
(a) Pest Species – Feeding on Plants
Adults and larvae of the subfamily Epilachninae feed on plants. In Florida, this subfamily is represented only by Epilachna borealis (Fabricius) and E. varivestis Mulsant. Epilachna borealis, the squash beetle, feeds on members of the squash family (Cucurbitaceae), and in Florida is restricted to the north, with a wide distribution in other states of the eastern USA. Epilachna varivestis, the Mexican bean beetle, feeds on members of the bean family (Leguminosae), and rarely has been found south of northern Florida. It is native to southern Mexico, but it is an immigrant to the USA, first detected in the west in 1849, and in northern Florida in 1930. Now, its distribution is from Costa Rica north through Mexico to the Rocky Mountain states of the USA, and with a separated eastern population (which extends southward to northern Florida). In Florida it can be controlled efficiently by releases of the parasitoid wasp Pediobius foveolatus (Crawford) (Eulophidae) (Nong and Bennett 1994), which have to be made annually in the northeastern USA (Stevens et al. 1975) because of the more severe climate. It was discussed by Sanchez-Arroyo (2009).
(b) Innocuous Species – Feeding on Mildews
Ladybirds of the tribe Halyziini (of the subfamily Coccinellinae) feed on fungal growths (mildews) on the leaves of plants. In Florida, this tribe is represented by the West Indian Psyllobora nana Mulsant and Psyllobora schwarzi Chapin which have invaded the extreme south of Florida, and by the widespread Psyllobora parvinotata Casey which also occupies coastal areas as far west as Louisiana.
(c) Predatory Species – Feeding on Mites
Adults and larvae of the tribe Stethorini (of the subfamily Scymninae) feed on tetranychid mites. In Florida, this tribe is represented only by Stethorus utilis (Horn), a tiny ladybird which is also distributed in the coastal plains of the southeastern states from North Carolina through Texas.
(d) Predatory Species – Feeding on Whiteflies
Four of Florida’s ladybirds appear to be more-or-less specialized predators of whiteflies. They are Delphastus catalinae (Horn), D. pallidus (LeConte), and D. pusillus (LeConte) (tribe Serangiini), and Nephaspis oculatus (Blatchley) (Tribe Scymnini). The first seems to be an immigrant species from the Neotropical region, with first Florida record in 1974 (Hoelmer and Pickett 2003). Deliberate attempts to introduce that species from California in 1916-1917 to Manatee County, Florida, seem to have had no success (Frank and McCoy 1993, Hoelmer and Pickett 2003). The next two (D. pallidus and D. pusillus) are considered to be native. The fourth (N. oculatus) may be an immigrant from Central America. After “D. pusillus” was found to be a very useful biological control agent against sweetpotato whitefly (Bemisia tabaci (Gennadius) (Hoelmer et al. 1993) including the “form” that later was named silverleaf whitefly (Bemisia argentifolii Bellows and Perring), “it” was exported to California and made available commercially and used in other parts of the USA. Unfortunately, the ladybird beetle that was called D. pusillus by Hoelmer et al. (1993) seems to have been a mixture of D. catalinae and D. pusillus (Hoelmer and Pickett 2003). Somehow this resulted in commercial biological control companies selling D. catalinae under the name D. pusillus (Hoelmer and Pickett 2003).
(e) Predatory Species – Feeding on Cottony cushion Scale
Cottony cushion scale (Icerya purchasi Maskell), native to Australia, belongs to the homopterous family Margarodidae (commonly called “ground pearls”, although this name hardly fits this species) in the superfamily Coccoidea (scale insects). It is a major pest of citrus, and an important pest of several other trees and shrubs including Acacia, Casuarina, and Pittosporum. After its arrival in California, presumably as a contaminant of imported plants, it threatened to ruin California’s citrus industry in the late 1800s. It was controlled by importation, release, and establishment (as classical biological control agents) of Rodolia cardinalis (Mulsant) and a parasitoid fly, Cryptochetum iceryae (Williston). When cottony cushion scale became a problem in Florida, the same two biological control agents were imported from California into Florida. R. cardinalis is a highly effective control agent for cottony cushion scale.
(f) Predatory Species – Feeding on Mealybugs
Mealybugs are the homopterous family Pseudococcidae, which includes some notable pests of plants. The most notable ladybird predator of mealybugs in Florida is Cryptolaemus montrouzieri Mulsant, a species native to Australia, introduced into California first in 1891, and sometime later from California into Florida. It has been marketed commercially as a control agent for mealybugs and is often effective, but has one unfortunate characteristic: its larvae produce waxy filaments making them look to the uninitiated like their mealybug prey. Many owners of plants have sprayed the larvae with chemicals in the mistaken belief that they are pests. This misidentification must be overcome by education. Cryptolaemus montrouzieri does not confine its attentions to mealybugs, and also eats soft scales (Coccidae) and armored scales (Diaspididae). Such a catholic diet is normal for a long list of Florida ladybirds, so that their diet cannot neatly be pigeonholed as armored scales or soft scales or mealybugs — they may eat some prey in all of these families, and a few of the larger ones may even eat an aphid from time to time. For that reason, many genera and species are placed below under Feeding on Scale Insects.
Figure. Adult twicestabbed lady beetle, Chilocorus stigma (Walker), (red spots are round). Photograph by J.P. Michaud, University of Florida
(g) Predatory Species – Feeding on Armored Scale Insects
Eight species in four genera seem to feed largely or entirely on armored scale insects (Diaspididae). They include Microweisea coccidivora (Ashmead), M. misella (LeConte), and M. ovalis (LeConte) of the tribe Microweiseini, Zilus horni Gordon, Z. eleutherae Casey, Z. subtropicus (Casey) and perhaps Zagloba bicolor (Casey) (its diet is a guess) of the tribe Scymnillini, and Cryptognatha nodiceps Marshall of the tribe Cryptognathini. One of these, Cryptognatha nodiceps, is not native, having been imported in the 1930s, released, and established as a classical biological control agent for coconut scale.
Figure. Adult Cycloneda sanguinea (L.), a lady beetle. Photograph by James Castner, University of Florida.
(h) Predatory Species – Feeding on Scale Insects
Thirteen genera containing 66 species are placed here into this large trophic group that has scale insects as its prey, meaning members of the superfamily Coccoidea (the scale insects). This superfamily includes various related families, notably Coccidae (soft scales), Diaspididae (armored scales), Pseudococcidae (mealybugs), Dactylopiidae (cochineal scales), Kermesidae (gall-like scales), Eriococcidae (felt scales), Cerococcidae (ornate pit scales), and Asterolecaniidae (pit scales). The ladybird genera are named below, each followed by a number in parentheses, representing the number of species known from Florida: Decadomius , Diomus , Nephus , Pharoscymnus and Scymnus (all in tribe Scymnini), Brachiacantha , Hyperaspidius , Hyperaspis and Thalassa (all in tribe Hyperaspini), Axion , Chilocorus , Curinus , Egius , and Exochomus (all in tribe Chilocorini), Rhyzobius (tribe Coccidulini), and Azya (tribe Azyini). However, there is at least some level of prey specialization in these that feed on scale insects, which seems not to be the case for the next-discussed trophic group (those that feed on aphids). Brachiacantha has a curious life history in that its larvae so far as is known feed on scale insects within ant nests.
Figure. Adult Harmonia axyridis Pallas, the multicolored Asian lady beetle. Photograph by Scott Bauer, USDA.
(i) Predatory Species – Feeding on Aphids
Adults and larvae of 12 of the remaining 13 Florida species (the tribe Coccinellini) probably feed primarily on aphids. They include Coccinella novemnotata Herbst, C. septempunctata L., Coelophora inaequalis ,Coleomegilla maculata DeGeer, Cycloneda munda (Say), Cycloneda sanguinea , Harmonia axyridis Pallas, Harmonia dimidiata (Fabricius), Hippodamia convergens Guérin-Méneville, Mulsantina picta (Randall), Naemia seriata (Melsheimer), Neoharmonia venusta (Melsheimer). Although the 13th species (Olla v-nigrum Casey) feeds on some aphid species, it has been shown to be an important predator of psyllids.
Although the 13th species (Olla v-nigrum Casey) feeds on some aphid species, it has been shown to be an important predator of psyllids (Michaud 2001).
Figure. Adult Coleomegilla maculata DeGeer, a lady beetle. Photograph by Russell F. Mizell, University of Florida.
It lists four ladybird species available from commercial insectaries:
Cryptolaemus montrouzieri Mealybug destroyer (mealybugs on citrus, ornamentals, and vegetables, and in greenhouses and interiorscapes).
Delphastus catalinae Whitefly predator (greenhouse, banded-winged, sweetpotato, woolly, azalea, hibiscus, cloudywinged, citrus and rhododendron whiteflies on ornamentals, vegetables, fruit, and citrus, and in greenhouses and interiorscapes).
Hippodamia convergens Ladybeetle (aphids, scales and thrips, in citrus, ornamentals, fruits and vegetables, and in greenhouses and interiorscapes). This species occurs in Florida but there still is a potential problem – some suppliers do not rear the beetles but collect overwintering adults from the mountains of eastern California – these overwintering adult beetles (a) may be heavily parasitized and many may die, and (b) 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 (also called Lindorus lophanthae) (hard and soft scales and mealybugs on ornamentals). All four species above are known from Florida.
Chilochorus nigrita was detected in 2007 as established in Florida, This new presence allows future importations into Florida from commercial producers elsewhere under Florida regulations.
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. It is the vendors who are required to obtain the permits for commercial shipments. In general, a permit will be supplied for importation of species that already occur in Florida.
1. Cryptolaemus montrouzieri Mealybug
2. Delphastus catalinae Whitefly
3. Hippodamia convergens Aphids
4. Pink spotted ladybug Potato beetle
5. Black Ladybirds Mites
6. Coleomegilla Moths
7. Brachiacantha Scale Insects
8. Twenty spotted ladybug Mildew
9. Orange spotted ladybug Scale insects
10. Fifteen spotted ladybug Aphids
The main predators of coccinellids are usually birds, but they are also the prey of frogs, wasps, spiders, and dragonflies. The bright colours of many coccinellids discourage some potential predators from making a meal of them. This phenomenon, called aposematism, works because the predators learn by experience to associate certain prey phenotypes with a bad taste. A further defence, known as “reflex bleeding”, exists in which an alkaloid toxin is exuded through the joints of the exoskeleton, triggered by mechanical stimulation (such as by predator attack) both larval and adult beetles, deterring feeding.