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Species
Basic Characteristics of an Insect
On the criteria of species diversity, distribution, and sheer
numbers, Insects must be regarded as the most successful class
of animals ever to live. There are over 700,000 species of insects
known, outnumbering all other forms of life combined. They are
distinguished from other classes in the Phylum Arthropoda by having
a body divided into three main parts: head, thorax, and abdomen.
Jointed Feet
All arthropods, including insects, are equipped with jointed appendages,
for which the phylum is named (from the Greek arthron,
"joint," and podus, "foot").
The appendages are variously modified for walking, feeding, sensory
perception, copulation, and defense. Several pairs of appendages
modified for piercing, sucking and chewing form the mouthparts;
the insect mouth is a very busy place when all its dexterous parts
go to work on a piece of food.
Reproduction
In insects, reproduction is usually sexual, with separate male
and female animals. Fertilization is usually internal. In most
species, sperm are deposited directly into the female's vagina
at the time of copulation, though in some species the male deposits
a sperm packet outside the female, who then picks it up. The female
reproductive system may also include a spermatheca, a blind sac
in which sperm may be stored for a year or more.
Though most insect species produce a multitude of eggs, some flies
produce live offspring, usually a single young at a time. Many
insects mate only once in a lifetime.
External Skeleton
The body of an insect is completely covered by the cuticle, an
exoskeleton (external skeleton) constructed from layers of protein
and chitin. The cuticle can be modified into a thick, hard armor
over some parts of the body or be paper-thin and flexible in other
locations, such as the joints of the appendages.
The exoskeleton protects the animal and provides points of attachment
for the muscles that move the appendages. To grow, an arthropod
must occasionally shed its old exoskeleton and secrete a larger
one, a process called molting.
Many insects have one or two pairs of wings that attach to the
dorsal side of the thorax. Since the wings are believed to have
developed from basal parts of the legs rather than whole appendages,
insects are able to fly without sacrificing any walking legs.
Insect wings may have first evolved as extensions that helped
ventilate the gills or aided in the swimming of aquatic larvae,
only later becoming organs for flight.
Endangered Species
There are many, many different kinds of terrestrial and freshwater
invertebrates in British Columbia. Most of these invertebrates
are arthropods - insects, spiders, and their relatives. It is
not known how many invertebrates can be found in the dry, warm
lowlands of the south Okanagan and Similkameen valleys, but we
estimate that perhaps 15 000 species live there.
Although many of these are common and widespread, some are confined
to the dry grasslands of the southern Interior - and there are
literally hundreds that are found nowhere else in the province.
These are inhabitants of the Great Basin grasslands and wetlands,
which extend only a few, narrow fingers north into Canada. Several
species of insects that are considered rare in this region include:
Beetles
The endangered Parowana Tiger Beetle (Cicindela parowana),
is an example of the Order Coleoptera (Beetles). Main characteristics
of these animals are that they have two pairs of wings, the front
ones are horny covers protecting the membranous hind wings. They
have biting and chewing mouthparts and complete metamorphosis.
Dragonflies
The endangered Vivid Dancer (Argia vivida), is an
example of the Order Odonata, the Dragonflies. This order has
two pairs of net-veined wings; biting mouthparts and an incomplete
metamorphosis.
Mantids
The endangered Ground Mantid (Litaneutria minor), is
an example of Order Mantodea. The main characteristics of all
of these animals within this order include: two pairs of horny,
membranous wings; biting and chewing mouthparts in adults; and
an incomplete metamorphosis.
Flies and Mosquitoes
The endangered Apiocerid Fly (Apiocera barri) and
the threatened Robber Fly (Megaphorus willistoni),
are examples of the Order Diptera. Mosquitoes are also members
of this order and possess the same main characteristics as these
flies: one pair of wings and, the hindwings modified to form balancing
halteres; sucking, piercing, lapping mouthparts; and complete
metamorphosis.
Butterflies and Moths
The endangered Mormon Metalmark (Apodemia mormo)
and the threatened Viceroy (Limenitis archippus),
are examples of Order Lepidoptera, the Butterflies and Moths.
Species belonging to this order share the characteristics of having
two pairs of wings covered with scales; hairy bodies; tubular
mouthparts forming a long coiled tongue for sucking; and complete
metamorphosis.
Ants, Bees and Wasps
The endangered Scoliid Wasp (Campsomeris pilipes)
is an example of the Order Hymenoptera. Ants, bees and wasps belong
to this order because they display the same main characteristics:
two pairs of membranous wings; head mobile; well-developed eyes;
chewing or sucking mouthparts; stingers (in some species); complete
metamorphosis; and many species are social.
The Thompson-Okanagan and Similkameen valleys of southern British
Columbia contain all of these species and more that are endangered
for a variety of reasons. Insects in these regions are primarily
threatened by loss or degradation of their habitats and are at
risk because their ecosystems are at risk. this section sponsored by: |
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