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ODONATA -- <Images> & <Juveniles> [Latest Classification] Please refer also to the following link for
further details Introduction Dragonflies and damsel flies are very abundant, but most are in tropical
and subtropical areas. There more
than 6,325 species known as of the year 2000. Most are brightly colored.
All are predaceous both as nymphs and adults. The nymphs are almost all aquatic and feed
on a wide variety of animals, including tadpoles, small fish and
crustaceans. The adults capture their
prey while in flight. The smaller
species feed on mosquitoes and flies
of similar size, while the larger species are able to capture the largest
Diptera. Diptera, Hymenoptera and
Lepidoptera constitute most of the prey.
Mesothemis simplicicollis Say feeds extensively
on adult Tabanidae in Louisiana, and Cacergates
leucostica Burm. and others of that
genus are effective predators of tsetse fly in Africa. They have been credited with marked
reductions in tsetse population densities (Clausen 1940/62). The order is generally very beneficial,
except in a few isolated cases such as in Russia where Aeshna cyanea Mull.
destroyed about half the honeybee population in some areas. This occurred at the time of extended
migrations and is attributed to a lack of the normal food supply. In America, Coryphaeschna ingens
Ramb. may at times cause serious losses to beekeepers (Clausen 1940/62). Lestes temporalis Selys is reported to be
harmful to deciduous fruit trees in northern Japan because of its habit of
making oviposition incisions in young shoots during July and August. Only trees located near water were
injured, however. Eggs are usually laid in incisions in stems of plants below the
water surface, in muck or in rotting logs or they may be placed directly in
the water while the females are in flight.
There is simple metamorphosis, and the nymphs leave the water when
mature. Further Description This order includes the
dragonflies Anisoptera and
Zygoptera. The name Odonata
is derived from the Greek odontos (tooth) because there are
conspicuous teeth on the mandibles.
The size ranges considerably with Megaloprepus coerulatus of
Central America and the Hawaiian Darner, Anax strenuus, being the
largest. The extinct dragonflies belongubg to the Protodonata (Meganisoptera)
were close ancestors. This order also includes
mayflies and several extinct orders in a group "Paleoptera." The way the wings are articulated and
manipulated and general, but smaller appearance, indicates this relationship. Odonata have large
rounded heads with large compound eyes and two ocelli. Their legs are designed for catching,
which is usually insects. There are 2
pairs of long, transparent wings that have independent movement. The abdomens
are much elongated. The chewing mandibles are situated under the head in the
adult. Most families show a
thickened structure called the pterostigma, which is located near the wing tip
and which is thought to serve in aerodynamics and vision and may also aid in
rapid wing movement. The nymphs have thicker
bodies and they are shorter than adults. They are apterous and have smaller
heads thann the adult. The labium is
modified to serve as a prehensile organ for catching prey. Damselfly nymphs absorb oxygen through
external gills located on their abdomen, while dragonfly nymphs obtain oxygen
through an organ located in the
rectum. To distinghish the two
groups, dragonflies are strong fliers with tough bodies. They hold hold their wings either out to
the side or out and downward when not flying. On the other hand, damselflies are not as strongly built, even,
and when at rest most species hold their wings folded back over the
abdomen. The eyes of dragonflies
cover most of the head and almost touch each other at the top, while in
damselflies there exists a larger gap between the eyes. All
species are aquatic or semi-aquatic as immatures and occur primarily around
lakes and ponds and other bodies of water However, many species range far
from water. They feed primarily on
other insects. Complex genitalia are
found among males. There are grasping cerci for holding the female and a set
of copulatory organs on the abdomen where the sperm are held after being
produced by the primary genitalia. The male has its copulatory organ on the
underside of the 2nd abdominal segment. The eggs are deposited
in water or on vegetation near water or other damp places. Pronymphs hatch and live from nutrients
that were left in the egg. They then pass through 9 to 14 molts as nymphs feeding extensively on other aquatic
organisms, including small fish. The nymphs change to pale flying teneral
immature adults followed by reproductive adults. = = = = = = References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Lohmann, H. 1996.
Das phylogenetische System der Anisoptera (Odonata). Deutsche
Entomologische Zeitschrift 106(9): 209-266. Rehn, A.
C. 2003. Phylogenetic analysis of higher-level relationships of Odonata.
Systematic Entomology 28(2): 181-240. Trueman, J. W.
H. 2008. Tree of Life Web Project –
Pterygote Higher Relationships. Trueman, J. W.
H. & R. Rowe. 2008. Tree of Life Web Project – Odonata. Dragonflies and
damselflies. |