PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
THORAX
The thorax is made up of 3 segments (from front to rear):
1 pair of legs on each .
PROTHORAX (1 st )
MESOTHORAX (2 nd )
METATHORAX (3 rd )
1 pair of wings and
1 pair of spiracles on each
All 3 thoracic segments may not be visible from above, eg beetles.
LEGS
Moths, mantids and
grasshoppers have
ears on their legs
Some legs
(and bodies)
are covered with
sensory hairs
Mole cricket,
front leg modified
for digging.
WINGS
Sound and
communication
Some
grasshoppers
and beetles rub
their rear leg and
forewing together.
Some male
crickets chirp on
hot summer
nights by rubbing
specialized parts
of their forewings
to attract females.
Honey bees'
wings stroke over
11,000 times per
minute, to make
their distinctive
buzz.
Mosquitoes beat
their wings in
flight to make the
w
Males have bushy
antennae which
are designed to
pick up on the
wing beat of their
mates.
House flies beat
their wings up to
200 times per
second to make
their familiar buzz.
ADULT INSECTS HAVE 6 LEGS (3 PAIRS)
There is 1 pair on each segment of the thorax.
LEGS ARE JOINTED AND HAVE 5 PARTS
Coxa (articulates with the sternum).
Trochanter (often overlooked, tiny).
Femur (the stoutest part).
Tibia (usually long and slender).
Tarsus of 1-5 segments, in adults the
last tarsal segment usually has a pair
of claws, larvae usually have one claw.
LEGS ARE OFTEN MODIFIED FOR SPECIAL PURPOSES,
not necessarily for locomotion:
Digging, eg mole crickets.
Catching prey, eg praying mantids.
Cutting leaves, eg leaf-cutting bees.
MANY, BUT NOT ALL INSECTS HAVE WINGS
There is 1 pair on the mesothorax and 1 pair on the metathorax.
WING STRUCTURE
Wings are usually formed of 2 layers of thin membrane strengthened
by a framework of tubular veins, the spaces between being known as cells.
In the early stages of development wings are present as wing buds which
are filled with blood and supplied with trachea (air tubes).
Wings are articulated to the sides of the thorax and connected
internally to strong muscle bands.
Wing venation is used for identification especially, in wasps and flies.
VARIATIONS include:
Some adults have no wings, eg female painted apple moth.
Some insects with wings cannot fly, eg German cockroach.
Hind wings modified to form clubs (halteres), eg flies.
Forewings modified to form hardened wing covers (elytra), eg beetles.
Forewings have a thickened front portion, the rest of the wing being
gauzy, eg true bugs (green vegetable bug).
Surface of wings may be covered with hairs or scales, eg butterflies.
Wings may be coupled together, eg butterflies.
Fly, hind wings
club-shaped (halteres).
Beetle, forewings
hardened (elytra).
Bug, forewing with
thickened portion.
Insects and allied pests - Biology 15