File: <aqamidge.htm> <Home>
CHIRONOMID MIDGES
-- Biological Control (Chironomus spp. --
Diptera, Chironomidae) (e.legner@ucr.edu)
Although usually not of public health
importance, chironomids are often bothersome pests in recreation and urban areas,
and also may be economically important when huge numbers threaten food
processing industry or contaminate hospital environments. The public often
perceives chironomids as mosquitoes, which stimulates a psychological fear of
them. Thus, they must frequently be controlled by abatement agencies. In the
early 1960\'s chironomids of the genus Chironomus
began to show resistance to insecticides that were used for their control in
urban storm drain channels and recreational lakes of southwestern California.
The Southeast Mosquito Abatement District in Los Angeles subsidized a study
with University of California, Riverside scientists to investigate biological
control alternatives. Research on
the biological control of Chironomidae has been in conjunction with mosquito
control, because the breeding habitats are often the same or similar. The
same natural enemy groups were investigated, which includes fish, hydra,
planaria and various aquatic insect predators. As with mosquitoes, fish have
given the most significant levels of control, with cichlids of the genera Tilapia and Oreochromis
being most important. A permanent classical biological control has been
achieved in the principal storm drain channels of Los Angeles with the
establishment of Oreochromis mossambica
(Peters) and Oreochromis. hornorum Trewazas there. Persistence of
these subtropical cichlids is facilitated by areas of warm water effluent
that is discharged into the storm channels from electrical power plants in
winter. Benthic
species of Chironomidae are grazed to control levels in these channels, and the
cichlid populations annually reach very dense populations, which by early
autumn show signs of starvation. Pelagic Chironomidae have increased in
abundance with reduced competition for food in the absence of benthic forms.
Fortuitously, pelagic species pose no public nuisance. Research revealed that
densities of principally Chironomus
decorus Johannsen larvae, declined markedly in detritus habitats
of the urban drainages of the Los Angeles basin, with the establishment of
the cichlids. However, density changes in another group of non-annoying
midges, Cricotopus and Tanypus species, were not pronounced
over a 9-yr study period. The effective foraging on Chironomidae in certain
substrates by very dense populations of the species of cichlids influences
the phenotypic characteristics of such substrates to produce chironomids.
Typically the insect-produced fish biomass in autumn can exceed 4 x 105
kg over a distance of 18 km of paved river channel, a phenomenon apparently
dependent indirectly on the availability of warm water effluent from a power
generating plant. The cichlids now range in the neritic zone along the
southwestern California coast, and their contribution to enhancing predatory
marine fish biomass may be significant. A native species of pupfish, Cyprinodon macularius
Baird & Girard, has also been shown to be an effective predator of
chironomid midges. This species might be superior to Gambusia for mosquito abatement as
well, being able to rely on other than mosquito food in periods of low
mosquito abundance (Walters & Legner 1980). Details of biological control
efforts against Chironomidae may be found in the following references. REFERENCES: Legner, E. F. 1973.
Book Review, "Biologische Schädlingsbekämpfung." by J. M. Franz.
Paul Parey-Verlag, Berlin. 298
pp., 16 fig. Bull. Entomol. Soc. Amer. 19(2): 126. Legner, E. F. 1983e.
Imported cichlid
behaviour in California. Proc. Intern. Symp. on Tilapia in
aquaculture, Nazareth, Israel, 8-13 May, 1983. Tel Aviv Univ. Publ. 59-63. (CLICK to view details) Legner, E. F. 1995. Biological control of Diptera of medical and
veterinary importance. J. Vector Ecology 20(1): 59-120. . (CLICK to view details) Legner, E. F. &
E. C. Bay. 1970a. The
introduction of natural enemies in California for the biological control of
noxious flies and gnats. Proc. Calif. Mosq. Contr. Assoc., Inc. 37:
126-129. . (CLICK to view details) Legner, E. F. &
R. A. Medved. 1972.
Predators investigated for the biological control of mosquitoes and midges at
the University of California, Riverside. Proc. Calif. Mosq. Contr. Assoc.,
Inc. 40: 109-111. . (CLICK to view details) Legner, E. F. &
R. A. Medved. 1973b.
Influence of Tilapia mossambica (Peters), T. zillii
(Gervais) (Cichlidae) and Mollienesia latipinna LeSueur
(Poeciliidae) on pond populations of Culex mosquitoes and chironomid
midges. J. Amer Mosq. Contr. Assoc. 33(3): 354-364. . (CLICK to view details) Legner, E. F. &
R. A. Medved. 1974b.
The native desert pupfish, Cyprinodon macularius Baird and
Girard, a substitute for Gambusia in mosquito control? Proc. Calif.
Mosq. Contr. Assoc., Inc. 42: 58-59. . (CLICK to view details) Legner, E. F. &
F. W. Pelsue. 1977.
Adaptations of Tilapia to Culex and chironomid midge ecosystems
in south California. Proc. Calif. Mosq. & Vect. Contr. Assoc., Inc. 45:
95-97. . (CLICK to view details) Legner, E. F. & F. W. Pelsue, Jr. 1983.
Contemporary appraisal of the population dynamics of introduced cichlid fish
in south California. Proc. Calif. Mosq. & Vect. Contr. Assoc., Inc. 51:
38-39. . (CLICK to view details) Legner, E. F., R. A.
Medved & W. J. Hauser. 1975b.
Predation by the desert pupfish, Cyprinodon macularius on Culex
mosquitoes and benthic chironomid midges. Entomophaga 20(1): 23-30. . (CLICK to view details) Legner, E. F., R. A. Medved & F. Pelsue.
1980b. Changes in chironomid breeding patterns in a paved river channel
following adaptation of cichlids of the Tilapia mossambica-hornorum
complex. Ann. Entomol. Soc. Amer. 73(1): 293-299. . (CLICK to view details) Walters, L. L. &
E. F. Legner. 1980.
Impact of the desert pupfish, Cyprinodon macularius, and Gambusia
affinis on fauna in pond ecosystems.
Hilgardia 48(3): 1-18. . (CLICK to view details) |