Overview

Brief Summary

Taxonomy

Females are easily recognised by the following combination of characters:
  • mid tarsi 4-segmented
  • fore-wing uniformly hairy - without any evident bare patches
  • body with head and mesosoma (thorax) black, metasoma (abdomen) bright yellow
E. formosa’s DNA has been sequenced for several different gene fragments, and these can be found on the Nucleotide, alphabet of life website with the following accession numbers: Mitochondrial: CO1: AY264337; Ribosomal:18S: AY918985; 5.8S and ITS1: AY615783; 28S: AY615760.Polaszek et al (1992) included E. formosa in the complex of parasitoid wasps that attack the whitefly pest Bemisia tabaci. Because of its more or less cosmopolitan distribution, E. formosa is included in identification keys to Encarsia species from Australia (Schmidt and Polaszek, 2007); China (Huang and Polaszek, 1998); Egypt (Polaszek et al 1999); Mexico (Myartseva and Evans, 2007) and U.S.A. (Schauff et al, 1996).Synonym: Trichaporus formosus (Gahan).
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Introduction

Encarsia formosa was first described by A B Gahan (1924) from a greenhouse population in Idaho, USA.The name formosa means ‘beautiful’ in Latin - and in this case has nothing to do with the former name of the island of Taiwan.Encarsia formosa is dependent on the whitefly to lay its eggs, and for food, killing it in the process. It parasitizes 16 different species of whitefly in different parts of the world.Each adult wasp can kill around 100 whitefly nymphs in its lifetime.
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Comprehensive Description

Biology

It is a solitary, primary endoparasitoid in the sessile, developmental stages of whiteflies (Aleyrodidae), known as ‘nymphs’ and ‘puparia’.Adult female E. formosa locate plants infested with whiteflies using their olfactory and visual senses, searching for hosts on the upper and undersides of leaves.As well as killing hosts by oviposition, female wasps also pierce whitefly nymphs with their ovipositor and feed on exuded haemolymph.Wasp eggs are unfertilised as E. formosa is a uniparental (thelytokous) species that does not need to mate to produce females. This characteristic is caused by infection with a recently-discovered bacterium - a Wolbachia species.E. formosa lays eggs preferentially in the third and fourth instar nymphs, and prepupae, laying about 5 eggs a day over a 12-day life span, thus laying about 60 eggs in total.Each female will also host-feed on about 3 nymphs every day. The total number of whitefly nymphs killed during a female’s lifetime is almost 100 (Hoddle et al, 1998).Thelytoky can be suppressed by destroying the Wolbachia bacteria with antibiotics fed to the adult females, or exposure to high temperature. However, males resulting from this treatment are not able to inseminate females (Kajita, 1989; Zchori-Fein et al, 1992).One of the important attributes leading to this wasp’s success is its very high degree of host-specificity. After almost a century of detailed study, it is known to develop successfully in just 16 species of whitefly hosts around the world.
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Physical Description

Type Information

Syntype for Encarsia formosa Gahan, 1924
Catalog Number: USNM
Collection: Smithsonian Institution, National Museum of Natural History, Department of Entomology
Preparation: Slide
Collector(s): R. Smith
Year Collected: 1920
Locality: Twin fall; Florida, Florida, United States
  • Syntype:
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Ecology

General Ecology

Distribution ecology

Encarsia formosa is a parasoid wasp that feeds on the nymphs and larvae of various species of whitefly including Aleurolobus malangae, Aleurolobus subtilis, Aleurothrixus floccosus, Aleurotrachelus trachoides, Aleyrodes lonicerae, Aleyrodes proletella, Aleyrodes singularis, Aleyrodes spiraeoides, Bemisia tabaci, Trialeurodes ricini, Trialeurodes vaporariorum.
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Vortex provides lift: parasitic wasp
 

The wings of one parasitic wasp generate lift by clapping together at the top of a stroke and then peeling off, creating a vortex that provides lift.

   
  "As an example, some types of small parasites, Encarsia, make use of a method called 'clap and peel.' In this method, the wings are clapped together at the top of the stroke and then peeled off. The front edges of the wings, where a hard vein is located, separate first, allowing airflow into the pressurised area in between. This flow creates a vortex helping the up-lift force of the wings clapping." (Yahya 2002:30)


In a flight mechanism called the clap and peel, "the wings clap together and peel apart serially from the leading to the trailing edge. The near-clap and partial peel differs in that the wings approach each other at the top of the stroke, but do not clap together.

"The clap and peel is characteristic of many insects with particularly broad wings, and has been recognized in some mantids and Orthoptera, Phasmida, chrysopid Neuroptera, and butterflies. The radiating veins and flexible cross-veins of the vannus of orthopteroids and dictyopteroids seem particularly to favor the peel, and also the partial peel. The relative breadth of the thorax may principally determine which of the two techniques is adopted: a broad thorax may effectively prevent a full clap.

"The clap itself appears to project a vortex ring, corresponding to a jet of air, and the broad wings of some butterflies at least seem to concentrate this jet by forming a hollow tunnel at the top of the upstroke." (Wootton 1992:127)
  Learn more about this functional adaptation.
  • Harun Yahya. 2002. Design in Nature. London: Ta-Ha Publishers Ltd. 180 p.
  • Lehmann, F; Sane, SP; Dickinson, M. 2005. The aerodynamic effects of wing–wing interaction in flapping insect wings. Journal of Experimental Biology. 208: 3075-3092.
  • Wootton RJ. 1992. Functional morphology of insect wings. Annual Review of Entomology. 37: 113-140.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Encarsia formosa

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1
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Wikipedia

Encarsia formosa

Encarsia formosa is a species of wasp and a well known parasitoid of greenhouse whitefly. The tiny females (about 0.6 mm long) are black with a yellow abdomen and opalescent wings. There are considerably fewer males than females. They are slightly larger and are completely black in coloration.

Life cycle[edit]

Tomato leaf with whitefly nymphs (white) parasitized by E. formosa (black).

Females deposit 50-100 eggs individually inside the bodies of third instar nymphs or pupae 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[edit]

Encarsia 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 Encarsia has seen something of a revival, with renewed usage in European and Russian greenhouses.[1] 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, which is a particularly difficult plant for predators to establish on.[2]

Flight[edit]

E. formosa makes use of an unusual form of hovering flight. Unlike normal flight, this method would work in an entirely inviscid medium, as it does not rely on a starting vortex to create circulation about the wing. Instead, the wingtips briefly touch at the apex of their stroke, altering the topology of the surrounding medium.[3][4]

References[edit]

  1. ^ [1] MS Hoddle et al. (1998) Annual Review of Entomology Vol. 43: 645-669
  2. ^ (http://www.bioforce.net.nz/products/enforce.html) Bioforce Limited, New Zealand
  3. ^ T. Weis-Fogh, Quick estimates of flight fitness in hovering animals, including novel mechanisms for lift production, J. Expl. Biol. 59, 169-230, 1973
  4. ^ M. J. Lighthill, On the Weis-Fogh mechanism of lift generation, J. Fluid Mech. 6 0, 1-17, 1973
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