Mealybugs are insects in the familyPseudococcidae, unarmored scale insects found in moist, warm habitats. Of the more than 2,000 described species, many are considered pests as they feed on plant juices of greenhouse plants, house plants and subtropical trees and also act as a vector for several plant diseases. Some ants live in symbiotic relationships with them, protecting them from predators and feeding off the honeydew which they excrete.
Mealybugs are sexually dimorphic: females appear as nymphs, exhibiting reduced morphology, and lack wings, although unlike many female scale insects, they often retain legs and can move. Males are smaller, gnat-like and have wings. Since mealybugs, as well as all other Hemiptera, are hemimetabolous insects, they do not undergo complete metamorphosis in the true sense of the word. However, male mealybugs exhibit a radical change during their life cycle, changing from wingless, ovoid nymphs to wasp-like flying adults.[citation needed]
Mealybug females feed on plant sap, normally in roots or other crevices, and in a few cases the bottoms of stored fruit. They attach themselves to the plant and secrete a powdery wax layer (hence the name "mealy" bug) used for protection while they suck the plant juices. In Asia, mango mealybug is considered a major menace for the mango crop. The males are short-lived, as they do not feed at all as adults and only live to fertilize the females. Male citrus mealy bugs fly to the females and resemble fluffy gnats.
Some species of mealybug lay their eggs in the same waxy layer used for protection in quantities of 50–100; other species are born directly from the female.
The most serious pests are mealybugs that feed on citrus. Other species damage sugarcane, grapes, pineapple (Jahn et al. 2003), coffee trees, cassava, ferns, cacti, gardenias, papaya, mulberry, sunflower and orchids. Mealybugs only tend to be serious pests in the presence of ants because the ants protect them from predators and parasites.[2] Mealybugs are also a vector of viruses in grapevines, spreading grapevine leafroll and grapevine red blotch viruses.[3]
Mealybugs also infest some species of carnivorous plant such as Sarracenia (pitcher plants). In such cases it is difficult to eradicate them without repeated applications of insecticide such as diazinon. Small infestations may not inflict significant damage. In larger amounts though, they can induce leaf drop. In recent years, some of the mealybug species have become invasive pests in localities posing a great problem to the new agro-ecosystems. In India, Withania somnifera plant have been reported as a new reservoir host for an invasive mealybug species Phenacoccus solenopsis.[4]
Fossil specimens of genus Acropygaants have been recovered from the Burdigalian stage Dominican amber deposits and several individuals are preserved carrying the extinct mealybug genus Electromyrmococcus.[6] These fossils represent the oldest record of the symbiosis between mealybugs and Acropyga species ants.[6]
Some gardeners use species of predatory beetles (e.g. Cryptolaemus) and green lacewings (Chrysopidae) larvae to control mealybug infestations, as the larval lacewings are voracious predators of aphids and other small insects.[8]
Metabolism
Mealybugs have a highly sophisticated metabolism that involves not one but two bacterial endosymbionts, one inside the other. The endosymbionts make essential amino acids that the mealybug is not able to acquire directly from its diet. Genetically, mealybugs rely on a "mosaic" of metabolic pathways in which proteins are transported across membranes between what were once independent organisms.[9]
Use in the textile industry
In Oaxaca Mexico, where mealybugs are known as cochinilla algodonosa, the insects are intentionally cultivated and farmed. Dried mealybugs are ground into a dust, producing a red dye is used to colour fabrics, in artist's paints, and in cosmetics.
Prickly Pear Cactus with Mealybugs
Mealybugs on Prickly Pear Cactus Leaves
Mealybugs being ground into traditional red dye in Oaxaca, Mexico
Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the superfamily Coccoidea due to taxonomic uncertainties. Adult females typically have soft bodies and no limbs, and are concealed underneath domed scales, extruding quantities of wax for protection. Some species are hermaphroditic, with a combined ovotestis instead of separate ovaries and testes. Males, in the species where they occur, have legs and sometimes wings, and resemble small flies. Scale insects are herbivores, piercing plant tissues with their mouthparts and remaining in one place, feeding on sap. The excess fluid they imbibe is secreted as honeydew on which sooty mold tends to grow. The insects often have a mutualistic relationship with ants, which feed on the honeydew and protect them from predators. There are about 8,000 described species.
Aspidiotus is a genus of armoured scales in the family Diaspididae. There are more than 100 described species in Aspidiotus.
Coccus is a genus of scale insects in the family Coccidae. Several species, such as Coccus viridis, a major pest of coffee, are major agricultural pests. The type species is Coccus hesperidumLinnaeus.
Aleyrodinae is a subfamily of whiteflies in the family Aleyrodidae.
Putoidae is a family of scale insects commonly known as giant mealybugs or putoids The genus name Macrocerococcus has also been used but it is now considered to be a synonym of Puto. The genus Puto was formerly classified as a member of the Pseudococcidae; however, it so significantly differed from the rest of the Pseudococcidae that it was accorded its own family Putoidae.
Diaspidina is a subtribe of armored scale insects. It occurs mostly in the Americas and Africa, with a few species in tropical Asia. In the Americas Pseudoparlatoria is the largest genus, with Diaspis second; in Africa Diaspis is the largest genus. The grouping identified by Balachowsky in 1954 as the subtribe Diaspidina, are now the tribe Diaspidini.
Hemiberlesia is a genus of armoured scales in the family Diaspididae. There are more than 50 described species in Hemiberlesia.
Parlatoria is a genus of scales and mealybugs in the family Diaspididae. There are at least 60 described species in Parlatoria.
Antecerococcus is a genus of scale insects. They are found worldwide but with greater abundance in the Old World. There are about 56 species:
Diaspidiotus is a genus of armoured scales in the family Diaspididae. There are more than 80 described species in Diaspidiotus, found worldwide.
Melanaspis is a genus of armoured scales in the family Diaspididae. There are more than 60 described species in Melanaspis.
Paracoccus is a genus of true bugs belonging to the family Pseudococcidae.
Planococcoides is a genus of true bugs belonging to the family Pseudococcidae.
Laminicoccus is a genus of mealy-bugs belonging to the family Pseudococcidae. The genus was first described in 1960 by Williams.
Ferrisia is a genus of mealybugs.
Eriococcus is the type genus of scale insects in the family Eriococcidae, erected by Targioni-Tozzetti in 1868. Species records have a world-wide distribution, but this genus name is known to be polyphyletic, so species placement is subject to change.
↑ Sharma, A.; Pati, P. K. (2013). "First record of Ashwagandha as a new host to the invasive mealybug (Phenacoccus solenopsis Tinsley) in India". Entomological News. 123 (1): 59–62. doi:10.3157/021.123.0114. S2CID85645762.
↑ SP290-S-Mealybugs on Ornamentals (Report). The University of Tennessee Agricultural Extension Service. 2003. SP290S-1.5M-5/03(Rev) E12-4615-00-030-03.
Jahn, G. C. and J. W. Beardsley (1994). "Big-headed ants, Pheidole megacephala: Interference with the biological control of gray pineapple mealybugs". In D.F. Williams [ed.] Exotic Ants: Biology, Impact and Control of Introduced Species. Boulder, Col.: Westview Press, 199–205. ISBN9780813386157.
Jahn, G. C. and J. W. Beardsley (1998). "Presence/absence sampling of mealybugs, ants, and major predators in pineapple". J. Plant Protection in the Tropics 11(1):73–79.
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