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Introduction to Insects: Structure, Function, Development and Feeding Behavior. Thomas J. Weissling Assistant Professor of Entomology University of Florida Fort Lauderdale Research. THE INSECTS. Fossil records indicate insects on land more than 300 million years ago - mid paleozoic.
Introduction to Insects: Structure, Function, Development and Feeding Behavior
Thomas J. Weissling
Assistant Professor of Entomology
University of Florida
Fort Lauderdale Research
crustaceans which were abundant in the oceans over 500 million
years ago. Trilobites are extinct:
but we are surrounded by crustaceans…most of which are aquatic.
Insects shared the terrestrial habitat with various relatives such
as spiders, ticks, mites, and scorpions.
that share the following characteristics:
1) Body segmented, the segments usually grouped in two or three
rather distinct regions
as the animal grows
University of Nebraska-Lincoln, Department of Entomology, Leon Higley
a tubular structure dorsal to the alimentary canal with lateral
openings in the abdominal region
7) The body cavity a blood
cavity or hemocoel, the
located above the alimentary canal, a pair of connectives
extending from the brain around the alimentary canal, and paired
ganglionated nerve cords located below the alimentary canal
10) Excretion usually by means of tubes (the Malpighian tubules)
that empty into the alimentary canal, the excreted materials
passing to the outside by way of the anus
12) The sexes nearly always separate
10+ legs, 2 body regions, mandibles, 2 pairs of antennae, no wings
1-2 pair of legs per segment, 2 body regions, mandibles, 1 pair of antennae, no wings
8 legs, 2 body regions, chelicerae, no antennae, no wings
6 legs, 3 body regions, mandibles, 1 pair of antennae, 0, 2, or 4 wings
are chelicerae which are not homologous to the mouthparts of
insects. They are an 8-legged group in an evolutionary line that
diverged from the insects in the mid-paleozoic
mandibles, maxillae and tracheal system but have only two body
regions, and they add segments as they molt (anamorphosis)
segments and legs were not added at molting (epimorphic).
Legs were retained on the three segments behind the head, and the
remainder of the body included only 11 segments
When the three segments with legs became capable of moving
the creature, the rest of the body became more specialized (for
reproduction, viseral functions, etc.)
Ended up with three body regions.
occupying the earth are insects
(approximately 1.5 million different
Less than 1%
to be pests
Beneficial or not
considered to be pests
1. Beneficial: (Pollination, Honey, Beeswax, silk [65-75 million
pounds produced annually], shellac, dyes, break down raw
materials, aerate soil, biocontrol of weeds and bad bugs, human
food, medicine & surgery [cantharidin (Spanish fly-blister beetle), bee venom for arthritis, blow fly larvae (maggot therapy)], research animal
2. Aesthetic Value: jewelry, pets, nice to look at
3. Injurious: plants, stored foods, woods, fabrics, humans and animals
essential in pest
1. Three, usually distinct body regions (head, thorax, and abdomen)
2. One pair of segmented antennae
3. Usually have one pair of compound eyes
4. Three pair of segmented legs, one pair on each of the three
5. Usually with two pair of wings, some have only one pair
(i.e., flies) or no wings at all.
as feeding and sensory perception.
Made up of 3 segments, the prothorax, mesothorax, and
metathorax. A pair of legs arise from each segment. Wings,
if present, arise from meso-, and meta-thorax.
Incomplete or gradual metamorphosis. The immatures, or
“nymphs” look similar to the adults (grasshoppers, aphids,
like the adult. The larvae pass through a pupal stage to change
into the adult form (wasps, beetles, moths, butterflies, flies).
is generally thought to directly affect absolute photosynthesis of
piercing/sucking or rasping mouthparts. Tend to remove plant
carbohydrates and nutrients after carbon is taken up but before it
is converted to tissue.
generally root and stem feeders that affect plants water and
nutrient balance. Severe reductions in water uptake results in
decreased turgor which decreases the expansion of new leaves,
stems and fruit. In addition, photosynthesis can be decreased.
results in direct destruction of harvestable produce which affects
quality, yield or both. Yield losses are not always proportional
to the damage.
Results in morphological changes in plant architecture. Can
result in reduction of physiological as well as harvestable yield.
Also gall forming insects.
Photos: University of Florida
University of Nebraska
University of California
Entomology And Nematology Department
Copyright University of Florida 2000
For more detailed information see the Featured Creatures WWW site at http://creatures.ifas.ufl.edu/