Encarsia formosa is a species of wasp and a well known parasitoid

Parasitoid

A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...

 of greenhouse whitefly

Greenhouse whitefly

Trialeurodes vaporariorum, commonly known as the glasshouse or greenhouse whitefly inhabits the world's temperate regions. It is a primary insect pest of many fruit, vegetable and ornamental crops, frequently being found in glasshouses and other protected horticultural environments...

. The tiny females (about 0.6 mm long) are black with a yellow abdomen and opalescent wings. There are many fewer males than females. They are slightly larger and are completely black in coloration.

Life cycle

Females deposit 50-100 eggs individually inside the bodies of third instar

Instar

An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...

 nymphs

Nymph (biology)

In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...

 or pupa

Pupa

A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...

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 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.

Flight

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

Starting vortex

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 in a fluid. It leaves the airfoil , and remains stationary in the flow...

 to create circulation about the wing. Instead, the wingtips briefly touch at the apex of their stroke, altering the topology

Topology

Topology is a major area of mathematics concerned with properties that are preserved under continuous deformations of objects, such as deformations that involve stretching, but no tearing or gluing...

of the surrounding medium.