''Metaphycus helvolus'' is a species of

parasitic wasp Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps ( Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later cau ...

in the family

Encyrtidae Encyrtidae is a large family of parasitic wasps, with some 3710 described species in about 455 genera. The larvae of the majority are primary parasitoids on Hemiptera, though other hosts are attacked, and details of the life history can be vari ...

native to South Africa. It is a parasitoid of soft scale insects and has been used in their

biological 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 als ...

in California and Australia.

Description

''Metaphycus helvolus'' is a tiny insect, the adult female being yellowish-orange and about long.

Ecology

The adult female ''Metaphycus helvolus'' seeks out suitable scale

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People * Jim Host (born 1937), American businessman * Michel Host ...

. Its most important host is Mediterranean black scale (''Saissetia oleae''), but it also parasitises brown soft scale (''Coccus hesperidum''), nigra scale (''Parasaissetia nigra''), hemispherical scale (''Saissetia coffeae'') and European fruit lecanium (''Parthenolecanium corni''). Choosing a first

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow o ...

to early third instar

nymph 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 ty ...

, it punctures the cuticle with its

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...

and lays an egg inside. This process takes several minutes, and is more likely to be successfully completed where there are no

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22,0 ...

s tending the scale insects. The wasp larva develops inside the scale nymph, killing it in the process, and emerges through a round hole that it chews. The wasp has several generations per year in mild climates, which is a faster reproduction rate than that of black scale. Adult wasps also feed on scale insect nymphs, puncturing them and consuming the liquid that exudes from the pierced hole.

Use in biological control

The black scale is a serious

pest Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant deemed to be detrimental to humans or human concerns ** Weed, a plant considered undesirable * Infectious disease, an illness resulting from an infection ** ...

citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is nati ...

in the Mediterranean region, East Africa, California, Mexico, Chile and Australia; in 1926 it was estimated to be causing over two million dollars-worth of damage in California each year. When ''M. helvolus'' was introduced into the state in 1937, it reduced black scale dramatically so that within four years, less than 1% of the citrus plantations had economically damaging populations of the scale insect. Following this success, the wasp was introduced into South Australia in 1942 and was effective in reducing the scale on citrus in Australia to the status of a minor pest.

References

{{Taxonbar, from=Q13847678 Encyrtinae Biological pest control wasps Hymenoptera of Australia Hymenoptera of Europe Hymenoptera of North America Insects described in 1926