2. FORAGING BEHAVIOUR OF DRAGONFLY ADULT AND
LARVAE
Presented by: Awais nazir
Roll No: 33
Supervisor : Dr. Azhar Abbas Khan Baloch
Subject : Insect Ecology
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3. INTRODUCTION
A dragonfly is an insect belonging to the order Odonata
Consist of short bristly antennae, compound
eye composed of nearly 30,000 lenses, thorax is in the
center for locomotion, head is a tough, rounded capsule,
chewing mouth part
Incomplete Metamorphosis (Egg, Nymph, Adult)
Fig 1: Metamorphosis Stage Fig 2: Adult Dragon Fly 3
4. BIOLOGY OF DRAGONFLY LARVAE
During all stages of their lives, dragonflies are fearsome
and efficient hunters
If dragonfly larvae were eight to sixteen inches long, as
they probably were 300 million years ago, we would dare
not swim in fresh water for fear of being attacked
Any moving, living thing could be prey for dragonfly
larvae, including other dragonfly larvae, daphnia,
mosquito larvae, tadpoles and even small fish
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Fig 3: Dragonfly with
Labeling
5. BIOLOGY OF DRAGONFLY LARVAE
Aquatic larvae are very visual; any nearby movement is
noticed.
Their antennae are very sensitive and are used as tactile
sensors, picking up even slight movement.
Prey is secured primarily through the use of the
powerful, extendable lower lip (labium) that is equipped
with “teeth.”
In as little as 1/100 of a second, the labium can be
extended out to 1/3 the length of its body, snagging the
victim with the teeth and delivering it to the waiting jaws
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7. FORAGING BEHAVIOR OF DRAGONFLY LARVAE
Some dragonfly larvae, such as the darners, stalk their prey
among the plants and detritus of their underwater jungle
These “crawlers” are able to see a moving target from a
distance of several inches and will slowly pursue prey in a
cat-like manner until within striking distance
Other larvae, such as the emeralds, skimmers and the long-legged
cruisers, are “sprawlers,” blending into the bottom
materials with camouflaging markings or by a build up of silt
on body hairs
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9. FORAGING BEHAVIOR OF DRAGONFLY
LARVAE
Sprawlers lay in wait with their antennae laid out on the
muck or sand until suitable prey happens by
A third hunting style is demonstrated by the “burrowers.”
Most clubtails
spike tails are burrowers who disappear below the sand
or silt, only their eyes and the tips of their abdomens are
visible.
They lunge at anything that comes within striking
distance
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Fig 6: Sprawlers
10. FORAGING BEHAVIOR OF DRAGONFLY LARVAE
Despite their skill as predators, the larvae are also heavily
preyed upon by fish, birds, predatory aquatic insects and
other dragonfly nymphs
Larval gills are located inside their abdomen and water must
be pulled in through the rectum and expelled for them to
breathe
To avoid predators they accelerate this process and
effectively become “jet propelled.”
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13. FORAGING BEHAVIOR OF DRAGONFLY ADULT
Adults are also fearsome predators that have even been
known to take down a hummingbird
Their hunting prowess is due in no small part to large
eyes, resilient and maneuverable wings, spiky legs that
form a snagging net and a powerful, muscular thorax
serving both the wings and the legs
Adult dragonflies capture exclusively live prey and
almost always while they are on the wing
Flying insects are located visually and smaller prey is
caught directly by the mouth
Larger insects are snared in a basket that the dragonfly
forms with its legs, transferring the food to its mouth after
it has been secured
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14. FORAGING BEHAVIOR OF DRAGONFLY ADULT
Prey is either eaten on the wing or from a perch
The hard parts of beetles and wings of butterflies, moths,
damselflies and other larger insects are discarded and
may be found below a favored perch by the observant
naturalist
If you can approach close enough to a chewing
dragonfly you will be able to hear them “crunch, crunch”
on the exoskeleton of their “McBug” sandwich.
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17. TEMPERATURE CONTROL
Because warmth is needed for activity and an efficient
metabolism, most dragonflies disappear to protected
perches on cool days or when the sun disappears behind a
cloud
Despite the fact that insects are “cold blooded,” many
dragonflies maintain an internal temperature as high as 110
degrees F.
This is accomplished by the burning of calories during
physical exertion and by staying in the sun
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18. TEMPERATURE CONTROL
A cold dragonfly preparing to get the day started will shiver
its wings to create heat in its thorax until it has warmed itself
enough to take flight
Some dragonflies, such as the Ebony Bog haunter, Stygian
Shadow dragon and the blue darners have adapted to
cooler weather
as a method of allowing early- or late-season emergence or
to take advantage of the plethora of insect life that becomes
active at dusk
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19. TEMPERATURE CONTROL
In hot, sunny weather it is important that dragonflies don’t
overheat
Cooling strategies include becoming less active, moving into
shade and changing their body position
The obelisk position orients the dragonfly’s abdomen
directly at the sun, thereby reducing the surface area
exposed to solar heating
Some dragonflies also point their wings forward and down in
order to reduce exposure to sunlight and, perhaps, to reflect
light and heat away from their bodies.
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20. TEMPERATURE CONTROL
Dragonflies drink by thrusting their bodies down onto the
water’s surface in a sequence of one to three splashdowns
Water is absorbed through the exoskeleton
Dew is also absorbed on cool mornings.
Some species will be seen flying well after sunset on
moonlit evenings or under street lights
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21. MIGRATION
Certain species of dragonfly migrate, either en masse or
individually
Dragonflies follow weather fronts, fleeing cold fronts in
the fall on their way south and chasing warm fronts in the
spring when moving north
Another seasonal migrator is the Variegated Meadow
hawk who may be seen in early spring returning from
year-round haunts in Oklahoma or Texas
It is risky business though, as April snow and cold can
strand and freeze thousands.
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22. WINTERING
Most winter beneath the ice in the larval form in a state of
diapauses, which is a sort of suspended animation
Other species, such as some of the meadow hawks, lay
their eggs along shorelines where the eggs will sit through
the winter until high water in spring washes them into the
lake
22 Fig 11: Meadow Hawks ( Dragonfly Species)
