''Comperiella bifasciata'' is a parasitic wasp species in the genus '' Comperiella'' in the family Encyrtidae. It is used in biological control of

California red scale ''Aonidiella aurantii'' or red scale is an armored scale insect and a major pest of citrus. It is thought to be a native of South China but has been widely dispersed by the agency of man through the movement of infected plant material. In the ...

and yellow scale of

citrus ''Citrus'' is a genus of flowering plant, flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as Orange (fruit), oranges, Lemon, lemons, grapefruits, pomelos, and lim ...

Description

''Comperiella bifasciata'' is a tiny black wasp with two white bars on the head. These are more prominent in females, which also have dark patches on the wings, giving them the appearance of having a forked tail; the wings of males are unblotched.

History

''C. bifasciata'' is a parasite of the red scale (''Aonidiella aurantii''), a major insect pest of citrus. This pest was accidentally brought into the United States in the second half of the nineteenth century, and is known there as California red scale. In attempts to try to control the red scale, in 1908 ''Comperiella bifasciata'', and two other parasitic wasps, were introduced into California from Japan. It failed to become established on red scale but was found by 1931 to have become established on yellow scale (''Aonidiella citrina''). It was later established that an error had been made and that it was not parasitising ''Aonidiella aurantii'' in Japan, but rather '' Aonidiella taxus'' and ''

Chrysomphalus bifasciculatus ''Chrysomphalus'' is a genus of scales and mealybugs in the family Diaspididae. There are about 16 described species in ''Chrysomphalus''. Species * ''Chrysomphalus aberrans'' Mamet, 1951 * '' Chrysomphalus ansei'' (Green, 1916) * ''Chrysomphalus ...

''. When imports of a different biological race were made from China between 1947 and 1949, the parasite did become established on red scale in California. These two types are identical in appearance and will hybridise in the laboratory, but maintain their separate identities in the field. In the

San Joaquin Valley The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven c ...

, wasps reared from yellow scale are always of the Japanese type while those raised from red scale are the Chinese type. It seems that the hybrid is not so well adapted as either of its parents, so

natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charle ...

eliminates it, thereby preserving the two distinct types.

Ecology

The larva of ''C. bifasciata'' is an

endoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

. The adult female seeks out third

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 or ass ...

and fourth instar female scale insects, but is prepared to oviposit in any stage except females that have already produced crawlers. Each egg is laid singly and the developing larva feeds inside its host as it grows. When it pupates, black

meconium Meconium is the earliest stool of a mammalian infant resulting from defecation. Unlike later feces, meconium is composed of materials ingested during the time the infant spends in the uterus: intestinal epithelial cells, lanugo, mucus, amniotic ...

pellets are deposited and get pushed to one side under the scale. When it emerges, the wasp chews a jagged-edged hole through the scale's body and scale. The

mummified corpse A mummy is a dead human or an animal whose soft tissues and organs have been preserved by either intentional or accidental exposure to chemicals, extreme cold, very low humidity, or lack of air, so that the recovered body does not decay fur ...

of the scale insect, with black meconium deposits inside, usually remains stuck to the host plant.

Use in biological control

In California, the most important parasite of yellow scale is ''C. bifasciata''. The California red scale is most easily controlled by using the ectoparasite '' Aphytis'', with ''C. bifasciata'' being unable to compete with ''Aphytis'' because the latter consumes the scale larvae including any developing ''C. bifasciata'' larvae that happens to be inside. However, in inland climates, such as in the

, ''Aphytis'' is less suitable for use and ''C. bifasciata'' is more effective.

References

{{Taxonbar, from=Q13474848 Encyrtidae Insects described in 1906 Endoparasites