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''Encarsia formosa'' is a species of chalcidoid
Females deposit 50-100 eggs individually inside the bodies of
wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
and a well known parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
of greenhouse whitefly, one of the first to be used commercially for biological pest control
Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...
, from the 1920s. They can use at least 15 species of whitefly
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described.
Description and taxonomy
The ...
as a host, including '' Bemisia tabaci'' and ''Aleyrodes proletella
The Cabbage Whitefly (''Aleyrodes proletella'') is a species of whitefly from the Aleyrodidae family. It has a global distribution.
Adults are 1,5 mm in length. They have white wings with four gray spots. The wings are white due to a po ...
.''
The tiny females (about 0.6 mm long) are black with a yellow abdomen and opalescent wings. This species reproduces asexually via thelytoky induced by Wolbachia
''Wolbachia'' is a genus of intracellular bacteria that infects mainly arthropod species, including a high proportion of insects, and also some nematodes. It is one of the most common parasitic microbes, and is possibly the most common reproducti ...
infection. Males are produced only rarely. They are slightly larger than females and are completely black in coloration.
Life cycle
Females deposit 50-100 eggs individually inside the bodies of nymphs
A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...
or pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
e of the host species. The wasp larvae develop through four instars in about two weeks at optimum temperatures. Parasitized greenhouse whitefly pupae turn black in about 10 days, while parasitized sweet potato whiteflies turn amber brown. Both are easily distinguished from unparasitized host pupae. Wasp pupation occurs within the whitefly body. Adult wasps emerge about 10 days later.
Use in biological control
''Encarsia formosa'' has been used as a natural pesticide to control whitefly populations in greenhouses since the 1920s. Use of the insect fell out of fashion due to the increased prevalence of chemical pesticides and was essentially non-existent by the 1940s. Since the 1970s ''E. formosa'' has seen something of a revival, with renewed usage in European and Russian greenhouses. In some countries, such as New Zealand, it is the primary biological control agent used to control greenhouse whiteflies, particularly on crops such as tomato, a particularly difficult plant for predators to establish on.Clap and fling flight
''E. formosa'' utilizes the clap and fling mechanism often seen in sub-mm insects. The wings, at the apex, and nearly touching, fling apart and generate strong vortices along the leading edge and wing tips. This mechanism works well in lowReynolds number
In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be dom ...
flight as the generated vortices remained attached through the stroke cycle. Flexible wings and bristles along the wing edges help mitigate the large drag forces that the insect must overcome. Unlike normal flight, this method would work in an entirely inviscid
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the in ...
medium, as it does not rely on a starting vortex
In fluid dynamics, the starting vortex is a vortex which forms in the air adjacent to the trailing edge of an airfoil as it is accelerated from rest. It leaves the airfoil (which now has an equal but opposite "bound vortex" around it), and remai ...
to create circulation about the wing.
References