Ladybugs: Characteristics, Classification, Reproduction

The

s ladybugs or coccinellids (family Coccinellidae) are a group of coleopterans that 
They comprise around 5,000 to 6,000 species characterized by vibrant colors with small spots or stripes on their elytra (hardened wings). Most shed small insects as well as mites; although we also find species that feed on plants, fungi, pollen and flower nectar.

Many of them are used in biological pest control programs to minimize and control the populations of aphids, whiteflies, scale insects and mealybugs that do so much damage to crops in different agrosystems.

Source: pixabay.com

The name ladybug or ladybird (in English), was used for the first time in medieval England, perhaps because it was believed that beneficial predators of plagues were a gift from the Virgin Mary, the “Lady” or lady (in English). Later in the United States the name ladybug was adopted.

Despite being widely used in biological pest control, some members of the family can be a nuisance, causing damage to crops, structural damage, allergies, displacement of native and beneficial species.

Therefore, the need has arisen to implement control programs to decrease populations through the use of entomopathogenic fungi, parasitic mites, nematodes and parasitic wasps.

Article index

  • one

    Characteristics

  • two

    Classification / taxonomy

  • 3

    Reproduction

  • 4

    Feeding

  • 5

    Biologic control

    • 5.1

      Entomopathogenic fungi

    • 5.2

      Bacteria

    • 5.3

      Parasites

    • 5.4

      Nematodes

    • 5.5

      Parasitoid mites

  • 6

    Representative species

  • 7

    References

Characteristics

Adult beetles are small (1-10mm in length), round or oval, slightly convex dome-shaped. The elytra or hardened wings that protect the hind wings present different colors with different patterns of spots or points (in Rhyzobius chrysomeloides  the spots are absent).  

In some species, the pattern of their spots is influenced by their diet, environmental temperature and season of the year. The color and pattern of the wing markings aid identification. The area behind the head, the pronotum, can also have a distinctive pattern.

The eggs are laid near their prey, in small groups protected by leaves and stems. The eggs of many species of beetles are small (1 mm in length on average), yellow or orange in color, oval in shape, and slightly flattened.

Source: pixabay.com

Depending on the species and the availability of food, the larvae grow from less than 1mm to approximately 1 cm in length, through four larval stages, in a period of 20 to 30 days. 

The larvae of many species are gray or black with yellow or orange bands or spots. They usually move in search of food, being able to travel up to 12 meters in search of their prey.

Classification / taxonomy

The Coccinellidae family belongs to the order Coleoptera (Linnaeus, 1758), suborder Polyphaga (Emery, 1886), infraorder Cucujiformia (Lameere, 1936), superfamily Coccinelloidea (Latreille, 1807), family Coccinellidae (Latreille, 1807).

The family is made up of more than 5,000 species, distributed in seven subfamilies: Chilocorinae (Mulsant, 1846), Coccidulinae (Mulsant, 1846), Coccinellinae (Latreille, 1807), Epilachninae (Mulsant, 1846), Hyperaspidinae (Duverger, 1989), Scymninae (Mulsant, 1876) and Sticholotidinae (Weise, 1901).

Reproduction

Members of the Coccinellidae family are holometabolic, that is, they have four stages of development: egg, larva, pupa, and adult. Female beetles can lay 20 to 1,000 eggs over a one to three month period, beginning in spring or early summer.

After the pupal stage the adults emerge, mate, search for prey, and prepare for hibernation. The beetles overwinter as adults, often in aggregations under leaf litter, rocks, and bark, with some species often taking shelter in buildings and houses.

Mating occurs primarily at aggregation sites, shortly before the beetles disperse after winter dormancy. Some members of the family are bivoltine (only two generations per year) and in others four to five generations can be observed per year.

In the first generation, after hibernating, all females are reproductive; In the second generation, a few females enter a state of physiological inactivity known as diapause; In the third and fourth generation, most females enter diapause.

Feeding

Adults and larvae of the Epilachinae subfamily feed on plants. An example of this is the Mexican bean beetle Epilachna varivestis , which feeds on members of the bean family.

On the other hand, ladybugs from the Halyziini tribe feed on fungi that grow on the leaves of plants. Others feed on pollen and nectar from flowers.

However, the vast majority of members of the Coccinellidae family prey on insects, mites, moth eggs, other species of beetles, and even, if food availability is scarce, they can be cannibals.

Source: pixabay.com

The adults and larvae of the Stethorini tribe are specialized predators of whiteflies, and the adults and larvae of the Coccinellini tribe are voracious predators of aphids and scale insects.

Among them we find the species Coccinella novemnotata (nine-point ladybird), C. septempunctata (seven-point ladybird), Coelophora inaequalis (Australian beetle), Coleomegilla maculata (spotted beetle) and Harmonia axyridis (multi-colored Asian beetle).

Biologic control

Coccinellids are widely used in biological control programs for phytophagous insects. Unfortunately they are voracious animals, capable of diminishing or displacing native and beneficial insect species.

Likewise, ladybug infestations can cause structural damage, allergies and significant damage to the cultivation of wine grapes, grains and vegetables.

Natural enemies such as pathogens, predators, parasitoids, nematodes and parasitic mites can be used in various ways to control invasive beetles.

Entomopathogenic fungi

Numerous studies have shown the effectiveness of the entomopathogenic fungus Beauveria bassiana on at least 7 species of members of the Coccinellidae family: Hippodamia convergens (convergent ladybug) , Adalia bipunctata (two-point ladybird), Coccinella septempunctata (seven-point ladybird), Coleomegilla maculata lengi (twelve-point ladybug), Serangium parcesetosum , Olla v-nigrum (grayish beetle) and Cryptolaemus montrouzieri (destructive or cochineal beetle).

The fungus penetrates the skin of the insect and once inside, it develops at the expense of the nutrients available in the hemolymph of its host. As the days go by, the insect stops feeding and dies.

Once dead, the fungus breaks the skin of the insect (from the inside out), covering it with spores that are dispersed with the wind, giving way to new infections.
In case of not causing the death of the animal, the infection can reduce oviposition.

Another effective species in the control of coccinellids is Hesperomyces virescens , capable of causing a 65% decrease in the population of beetles, especially members of the species Harmonia axyridis and A. bipunctata . The infection spreads through copulation.

Bacteria

Members of the genus Adalia sp., Adonia sp., Anisosticta sp., Calvia sp., Cheilomenes sp., Coccinella sp., Coccinula sp., Coleomegilla sp., Harmonia sp., Hippodamia sp. and Propylaea sp., have been affected by infections of bacteria belonging to the genera Rickettsia sp., Spiroplasma sp., Wolbachia sp., Flavobacteria sp., c-proteobacterium sp.

Sometimes the infection kills only males during embryogenesis. In other cases, the infection generated inhibits feeding and prevents

oviposition.

Parasites

Among the parasitoids, we find the braconid wasp Dinocampus coccinellae , an ectoparasite of ladybugs common in Europe, Asia and America. The female wasps lay their eggs in the abdomen of the beetles, allowing the development of the wasp inside the beetle.

Once outside, the wasp can also attack larvae and pupae of coccinellids. The species Cocinella undecimpunctata , C. septempunctata , and H. quadripunctata have been shown to be vulnerable to its attack.

Nematodes

On the other hand, the nematodes of the families Allantonematidae, Mermitidae, Heterorhabdhitidae and Sternernemitidae are capable of significantly reducing the maturation of the eggs of the species Proylea quartuordecimpunctata ,   Oenopia conglobatta , H. axyridis and C. semtempunctata .

Parasitoid mites

Another case of parasitism is found in the mite Coccipolipus hippodamiae (Acari: Podapolipidae), an ectoparasite of coccinellids from Europe. The larva of C. hippodamiae is found on the ventral surface of the beetle elytra and is sexually transmitted through copulation. Once in its new host, the mite travels to the insect’s mouthparts, feeds on the hemolymph, and develops within the adult.

After a few weeks, the surface of the elite will be covered with eggs, larvae and adults. The most susceptible coleopteran species are A. bipunctata and A. decempunctata .

Representative species

The species Epilachna borealis (squash beetle) and E. varivestis are herbivorous and can be highly destructive agricultural pests on plants of the squash (Curcubitaceae) and bean (Leguminosae) families.

The species Harmonia axyridis,  like Coccinella septempunctata , are voracious predators capable of displacing populations of native and beneficial insects. Furthermore, H. axyridis has become a pest in fruit crops, mainly wine grapes. Despite this, for a long time it was used for the biological control of aphids.

Likewise, the species Hippodamia convergens  is used to control aphids, scale insects and thrips in citrus fruits, fruits and vegetables in greenhouses and indoors.

The species Delphastus catalinae (synonym Delphastus pusillus ) is an avid whitefly predator in greenhouses and indoors. Cryptolaemus montrouzieri is also used in control programs against mealybugs, and the Olla v-nigrum species is an important predator of psyllids, insect pests that usually attack ornamental and nightshade plants.

References

  1. Shelton, A. Lady Beetles (Coleoptera: Coccinellidae). Biological control a guide to natural enemies in north america. Cornell University. Taken from biocontrol.entomology.cornell
  2. Standard ITIS report page: Coccinellidae. Integrated taxonomic information system. Taken from itis.gov
  3. Family Coccinellidae- Lady Beetles. Taken from bugguide.net
  4.  Kenis, M., H. Roy, R. Zendel & M. Majerus. Current and potential management strategies againts Harmonia axyridis . BioControl. 2007 Oct. DOI: 10.1007 / s10526-007-9136-7
  5. Riddick, E., T. Cottrell & K. Kidd. Natural enemies of the Coccinellidae: Parasites, pathogens, and parasitoids. BioControl. 2009 51: 306-312

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