Horny
insects.
Insects are arthropods,
having a hard exoskeleton, a three-part body (head, thorax,
and abdomen), three pairs of jointed legs, compound eyes,
and two antennae. The head holds, mainly, the large compound
eyes, the antenna (feelers), and the mouthparts. The legs
(and wings, if applicable) are attached to the thorax.
On most Insects, the abdomen is not an outstanding feature
composed of 11 segments. On grasshoppers, there is a large
round disc on the first segment next to the thorax. It
is called a tympanum and is the grasshopper's ear. And
on each abdominal segment, there is a small breathing
hole called the thoracic spiracle.
Insects are the most diverse group of animals on the planet.
There are approximately 2,200 species of praying mantis,
5,000 dragonfly, 20,000 grasshopper, 82,000 true bug,
120,000 fly, 110,000 bee, wasp ant and sawfly, 170,000
butterfly and moth, and 360,000 beetle species described
to date. Estimates of the total number of current species,
including those not yet known to science, range from two
million to fifty million, with newer studies favouring
a lower figure of about six to ten million. With over
a million described species more than half of all known
living organisms with estimates of undescribed species
as high as 30 million, insects potentially represent over
90% of the differing life forms on the planet. They are
most diverse at the equator and their diversity declines
toward the poles. Insects may be found in nearly all environments
on the planet, although only a small number of species
occur in the oceans, a habitat dominated by another arthropod
group, the crustaceans.
Insects possess segmented bodies supported by an exoskeleton,
a hard outer covering made mostly of chitin. The segments
of the body are organized into three distinctive but interconnected
units, or tagmata; a head, a thorax, and an abdomen. The
head supports a pair of sensory antennae, a pair of compound
eyes, if present, one to three simple eyes, if present,
("ocelli") and three sets of variously modified
appendages that form the mouthparts. The thorax has six
segmented legs (one pair each for the prothorax, mesothorax
and the metathorax segments making up the thorax) and
two or four wings (if present in the species). The abdomen
(made up of eleven segments some of which may be reduced
or fused) has most of the digestive, respiratory, excretory
and reproductive internal structures... |
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