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DIPTERA, Chironomidae -- <Images> & <Juveniles>
Description
& Statistics The true midges are primarily aquatic, although some develop in
decaying vegetable matter or manure or in the soil. Aquatic species feed on algae, decaying vegetable matter, small
crustaceans, etc. Members of the
subfamily Tanypodinae subsist largely on the larvae of other
Chironomidae. However, Trissocladius
equitans Claas, seems to be a true external parasite of the nymphs of a
mayfly, Rithrogena (Claassen 1922).
Larvae of various instars except the
first were found on the mesothorax under the wing pads, and the head was
embedded in the tissues. A sheet of
silk is spun over the body and is attached along its entire margin to the
body f the host, so that no outside feeding can take place. The larva is thus closely confined to the
body of the host. In younger
developmental stages, the larva lies across the host's abdomen, but later it assumes
a V-shaped position. Pupation occurs
beneath the web, and the pupa works its way out from beneath this covering to
ascent to the water surface just before emergence of the adult. Dactylocladius
brevipalpus Galt was recorded as
parasitic on mayfly nymphs of Rithogena
sp. and other genera in France. The
larvae were found only beneath the wing pads, and the species is believed to
be a true parasite rather than a commensal (Dorier 1938, Clausen 1940). Chironomids or non-biting
midges) are a family of nematoceran flies with a global distribution. They
are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae.
Many species superficially resemble mosquitoes but they lack the wing scales
and elongate mouthparts of the Culicidae. This is a large group of insects
with over 5010 described species and 705 species in North America alone. Males are easily recognized by their
plumose antennae. Adults are sometimes known as "lake flies" in
parts of Canada, as "sand flies", "muckleheads", or
"muffleheads" in various regions of the USA Great Lakes area, and
as "blind mosquitoes" or "chizzywinks" in Florida, North
America. Their amazing biodiversity often goes unnoticed because Chironomidae
are notoriously difficult to identify and are usually recorded by species
groups by ecologists. Each morphologically distinct group consists of a
number of morphologically (sibbling) identical species that can only be
identified by rearing adult males or by cytogenetic analysis of the polytene
chromosomes. Polytene chromosomes were originally observed in the larval
salivary glands of Chironomus midges by Balbiani in 1881. They form
through repeated DNA replication
without cell division, resulting in characteristic light and dark banding
patterns which can be used to identify inversions and deletions which allow species
identification The larvae can be found
in almost any aquatic or semiaquatic habitat, including treeholes,
bromeliads, rotting vegetation, soil, and in sewage and artificial
containers. They form an important fraction of the macro zoobenthos of most
freshwater ecosystems. They are often associated with degraded or low
biodiversity ecosystems because some species have adapted to virtually anoxic
conditions and are dominant in polluted waters. Larvae of some species are
bright red in color due to a hemoglobin analog; these are often known as
"bloodworms". Their ability to capture oxygen is further increased
by making undulating movements. Adults can be
pestiferous when they emerge in large numbers. They can damage paint, brick,
and other surfaces with their droppings. When large numbers of adults die
they can build up into malodorous piles. They can provoke allergic reactions
in sensitive individuals. Larvae and pupae are
important as food items for fish such as trout and other aquatic organisms.
The flying midges themselves are also eaten by fish, and insectivorous birds
such as swallows and martins. The larvae are consumed by certain amphibians,
such as the rough-skinned newt. They are also used
by fly anglers, who design and tie imitators to catch trout. They are also important as indicator organisms, i.e., the presence,
absence, or quantities of various species in a given body of water can
indicate whether pollutants may be present. Their fossils are also widely
used by palaeolimnologists as indicators of past environmental changes,
including past climatic changes. References: Please refer to <biology.ref.htm>, [Additional
references may be found at: MELVYL
Library ] Clausen, C.
P. 1940.
Entomophagous Insects.
McGraw-Hill Book Co., NY. & London. 688 p. |