Collection and preservation of insects
COLLECTION,KILLING AND PRESERVATION OF INSECTS
The five steps in the collection, Killing and preservation of insects are
1. Collection
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2. Killing
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3. Preservation
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4. Storage and
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5. Display
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Why?
To study about the insect.
When?
Early morning and late evening.
Where?
ü In the air
ü In fresh or brackish water
ü On the foliage or stems of trees and Shrubs
ü On the ground or near the roots of plants
ü Internally in plants, plant products, seeds, and fruit
ü among debris
ü In the nests or habitations of animals and man
ü In the soil
ü On or in other insects or animals
How?
Various methods and equipments have been used
to collect insect from different habitats. The following devices are used to
collect wide range of insects from different habitations.
a.
Insect net / Aerial net:
It
is used to collect flying insects like butterflies, dragonflies,
grasshoppers, antlions, flies,wasp and
bees.
b.
Aspirator / Pooter:
It is used to collecting small
insects by sucking them into a container. An aspirator consists of a glass
vial, with a stopper pierced by two flexible tubes. The end of one of the tubes
is covered by a small piece of gauze to prevent specimens from being drawn into
operator’s mouth. The specimens are collected by sucking on the end of the
gauze- covered pipe while holding the end of the other tube close to them. .
Ex: white flies, Jassids.
c.
Berlese funnel:
It is
used to collect soil dwelling insects. It comprises of a funnel on which a wire
gauge is kept. And a container filled with poison is kept under the funnel. The
soil / organic sample is kept over the gauge over that a heat emitting bulb is
switched on. Due to the heat, insects move downward and get collected in the
container.
d. Light Trap:
It
can be used to collect nocturnal insects (which are active during night).
ex. Moths.
e.
Dip net or Dipper
It is used
to collect aquatic insects
f.
Pit fall trap
Container such as plastic buckets, plant pots,
glass jars or tins are sunk into the ground to trap flightless, ground-living
insects. ex:ground beetles, cockroaches, crickers.
g.
Malaise trap
It resembles a tent with two open sides. A vertical
gauze wall in the middle intercepts flying insects, which are directed upwards
into a killing bottle fixed to the highest point of the trap. Malaise trap is
mainly used to catch bees, wasps and flies.
h.
Beating sheets
Well camouflaged or hidden species on plants are
best collected with a beating sheet. This method is useful for collecting
sessile or wingless groups such as some beetles, bugs, stick insects and
caterpillars.
i.
Suction trap
Suction traps draw specimens into a receptacle or
net by creating a down-draught. They are used to collect small flying insects
such as flies, aphids and wasps.
II. Killing:
Killing
should be done immediately after capture. Insects are killed either
mechanically or by using chemicals. There are two types of killing agents.
- Mechanical methods
a)
Pinching
Larger butterflies can be stunned or killed by
pinching the thorax between the thump and fore-finger.
b)
Freezing
Insects can be killed by placing them in a freezer.
This method is particularly suitable foe reared moths and butterflies. Care
should be taken to ensure the specimens are dead before removing them from
freezer, which may take up to 48 hours.
- Chemical methods
a.
Liquid killing agents
Ex:
Chloroform, Ethyl acetate and carbon tetra chloride can be used to kill the
insects.
Ethyl
acetate bottles/ Killing agent:
ü Make a paste
of plaster of paris and water, and place a thick layer on the bottom of a
bottle.
ü Allow the
plaster of paris to dry in a well ventilated place.
ü Saturate the
plaster of paris with ethyl acetate. Any excess liquid should be poured off.
ü Place crumbled
absorbent paper on top of the plaster of paris.
ü Let the bottle
dry out before recharging it with ethyl acetate.
b.
Solid killing agents
Ex: Potassium cyanide, Sodium
cyanide, Calcium cyanide are the common solid killing agents.
Cyanide bottle/
Poison bottle:
ü Wide mouthed
strong glass bottle or vial with a tight lid can be used.
ü Place a layer
of potassium cyanide (¼ inch) at the bottom.
ü Cover it with
a layer of dry Plaster of Paris (1/2inch).
ü Tap it with
wet Plaster of Paris (1/2 inch) and allow drying.
III. Preservation:
Insects can be
permanently preserved either dry or in liquid. The method of preservation
depends on the type of insect.
a. Wet preservation / liquid preservation:
Soft
bodied insects can be preserved in liquid preservatives like ethyl alcohol (70%)
and formalin (4%). Ex: Eggs and immature stages.
b.
Dry preservation:
Relaxing chamber: Relaxing
the dried specimens will prevent breakage. A relaxing jar is easily constructed
by placing 5 cm of sand in the bottom of glass jar. The sand is then saturated
with water, to which a few drops of formalin or carbolic acid crystals have
been added to prevent mold growth.
(i).
Direct pinning
Rust proof nickel
coated entomological pin was used to pin the insect. They are available in various
sizes as 000, 00, 0,1,2,3,4,5,6, &7.
Minuten
pins/Micro pins:
They are very thin,
slender, delicate and headless pins.
Pinning
Position:
Pinning
region
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Example
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Pronotum
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Cockroach, Grasshopper
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Scutellum
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Bugs
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Right elytra
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Beetles and weevils
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Mesothorax
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Moths, Butterflies, Bees, Wasps, Dragonflies
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(ii)
Indirect pinning or Double Mounting:
There are three types
of double mounting.
Carding: A rectangular (5 x 8 mm or 5 x 12 mm) white card
or celluloid bit may be used.
Pointing: The insect specimen is glued to a triangular card
(10 x 5 mm)
Staging: The stage is a narrow rectangular piece of pith or cork. Small insects
are pinned with micropins onto the stage. Then the stage is pinned with a
bigger pin.
- Display:
Display: Glass topped boxes for displaying insects
Ricker mount: Glass or
transparent cover topped, cotton filled, wooden box.
Storage boxes: Wooden boxes
of 45 x 30 x 15 cm
Labelling: Labels (Locality and Taxonomic) are must for
every collection.
Setting board
/ Spreading board:
It
is used for setting the wings of butterflies. It has wooden board with a
central groove in the middle and flat cork strips glued on either side of the
groove. Using paper board strips, the spread wings can be set
Pinning
Block: It is used to keep mounted specimen labels in a uniform height.
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