|
|
4-H Study Materials
for Entomology Contests
|
January 2003
|
VII. Collection
and Preservation of Insects
Why Collect Insects
The insect world includes some
of the most fascinating creatures ever to exist on earth. In size,
they range from microscopic to several inches in length. Many exhibit
dazzling, bright color patterns. Some insects are harmful to plants,
animals and man, but most insects are beneficial. Some insects, like
honey bees, have been cultured by man for many generations.
Insects may be collected as a
hobby and for the enjoyment of observing them as a part of nature. They
may also be collected for scientific studies. There is no better way
to learn about insects than to collect them.
When and Where to Collect
Insects
Insects are present in virtually
every habitat. The more places a person looks for insects the greater
will be the variety collected. Insects may be found flying in the air
or buried in the soil. They may be found in the water, on vegetation
or under logs, stones and debris.
Insects are most abundant in
the spring and summer. However, insects can be collected any day of
the year. Some species can be found under bark, in rotting logs or
under debris even on the coldest day of the year.
Certain insects, such as moths,
are active at night and may best be collected at night. Others, such
as dragonflies and most beetles, are active during the day and are therefore
collected more easily during the day.
Collecting Equipment
Many insect specimens are lost
because proper equipment, such as a net, vial of alcohol or killing jar,
is not available at the time the specimen is sighted. The collector
should be equipped to take advantage of any opportunity that may be encountered.
Containers. The
collector should be equipped with a variety of containers in which to hold
specimens collected. Many prize specimens are damaged or ruined because
of inadequate containers for holding and transporting. Containers should
be large enough to accommodate specimens without cramping or bending them. This
requires large containers for dragonflies, butterflies, and other large,
delicate insects. Adequate containers should be provided to prevent
crowding as well as to isolate rare or delicate specimens. Some of
the most available containers collectors use include:
Sweep net. A sweep
net is one of the most important pieces of equipment an insect collector
should have. With a sweep net, the collector can capture flying insects
and insects found on vegetation. The net may also be used to collect
aquatic insects. However, nets designed for collecting aquatic insects
are heavier than most sweep nets.
Beating cloth. A
beating-cloth or beating umbrella may be placed beneath vegetation. The
vegetation is then shaken or beaten with a stick. Insects dislodged
from the bush or shrub fall on the beating cloth and can be collected.
Aspirator. An aspirator
acts like a miniature vacuum cleaner. It is used to collect small insects.
Light traps. Light
traps are used at night and attract a wide variety of night-flying insects. Many
varieties of light traps exist. Some collect the specimens alive and
others draw the insects into a killing agent, such as alcohol or cyanide.
Bait traps. Bait
traps are useful in collecting many beetles and flies. The design of
bait traps varies from elaborate devices to a simple tin can buried to soil
level and baited with carrion or decaying fruit. The ingenious collector
will succeed in constructing a trap to fit his or her needs and desires.
Bait. An effective
bait can be made with fresh fruit. Fill half of a 1-gallon container
with mashed fruit, such as peaches and/or bananas, and add a cup of sugar. Allow
it to stand for about a week, but do not cover it tightly. During this
week, add a little more sugar to the mixture each day to continue the fermentation
process. Yeast can be added to speed up the process. Before using
the bait, add about a cup of brown sugar to the mixture. Apply the
bait with a brush to the trunk of trees in the early evening. By nightfall
there should be plenty of insects ready to be collected.
Light sheets. A
simple white sheet with a bright light source shining on it can be hung outside
at night. This is an effective way to attract moths and other nocturnal
insects. Blacklights, mercury vapor lights or incandescent lights are
all good for attracting insects.
Berlese funnels. An
effective trap for collecting Collembola and other small soil insects is
the Berlese funnel. This trap can easily be made by placing wire mesh
into a funnel. Position the funnel over a jar of alcohol and place
a bright light source over the top of the funnel. Add some soil and
leaf litter to the funnel, turn on the light and wait 3 to 4 hours. The
small insects in the material will try to escape from the light by burrowing
down further into the material, past the wire mesh and into the jar of alcohol. Use
an eye dropper to remove the insects from the alcohol.
Killing apparatus. Killing
jars may be constructed in a number of ways. All consist of a container
(usually a jar) with a killing agent. Select a jar that has a tight
lid that is easy to open and close. Use a jar that is large enough
to hold the insects you will collect. A wide-mouth quart jar is probably
the largest size needed, but smaller jars are more useful.
It is always a good idea to add
a paper towel or a few tissues to the jar to absorb moisture that will accumulate
in the jar. Some collectors prefer to line the bottom of the jar with
plaster of paris about an inch thick. To prepare jars using this technique,
mix the plaster of paris with water, pour it into the jar and let it dry
before you use it.
The most common killing agent
used in killing jars is ethyl acetate (finger nail polish remover). Only
a few drops of ethyl acetate are needed in a killing jar because the vapor
kills the insects. You may need to add a few drops each day or whenever
the insects do not die quickly. As an alternative to killing agents,
insects may be killed by placing them in a freezer overnight.
Remember that some insects should
be killed and preserved in alcohol. Rubbing alcohol is good to use
for this purpose. Vials or small bottles containing alcohol are needed
to separate insect specimens for proper maintenance of the collection.
Other equipment. A
variety of other equipment and tools will come in handy on any collecting
trip. Some of the equipment a collector should have are:
Preservation of Insect Specimens
Properly preserved insect specimens
will last indefinitely. There are various ways of preserving insects. The
proper method is based upon the type of insect to be preserved. Most
are mounted dry on pins. Many small specimens are best glued to small
cardboard points mounted on pins. Some are preserved in alcohol and
others may be mounted on microscope slides. The following list will
aid in determining what method should be used for killing and preserving
different adult insects.
Kill and preserve in alcohol;
mount on slides:
Anoplura (sucking lice)
Collembola (springtails)
Mallophaga (chewing lice)
Siphonaptera (fleas)
Thysanoptera (thrips)
Kill in ethyl acetate; mount
on pins:
Blattaria (roaches)
Coleoptera (beetles)
Dermaptera (earwigs)
Diptera (flies): Tiny ones may
be killed and preserved in alcohol.
Hemiptera (bugs): Kill in ethyl
acetate vapor or alcohol; mount on pins.
Homoptera (aphids, scale insects
and whiteflies): Kill and preserve in alcohol. Some may be mounted
on slides.
Hymenoptera (bees, wasps, ants,
etc.): Small gall wasps and parasites may be killed in alcohol.
Lepidoptera (moths and butterflies)
Mantodea (mantids)
Mecoptera (scorpionflies)
Odonata (dragonflies)
Neuroptera (lacewings, antlions,
etc.)
Orthoptera (crickets, grasshoppers)
Phasmida (walkingsticks)
Trichoptera (caddisflies)
Kill and preserve in alcohol:
Ephemeroptera (mayflies)
Isoptera (termites)
Plecoptera (stoneflies)
Psocoptera (booklice)
Thysanura (silverfish)
Larvae of insects should be killed
in boiling water and allowed to remain in the water until they float to the
top which takes from one to five minutes, according to size, then preserved
in alcohol.
Centipedes, millipedes, mites,
spiders, ticks and other small arthropods, although they are not insects,
are frequently handled by entomologists. All these should be killed
and preserved in alcohol. The smaller ones are usually mounted on slides.
Pinned specimens. Properly
pinned specimens are valuable and useful. Improper pinning detracts
from the looks and value of any specimen.
Common household pins should
not be used to pin specimens. Special insect pins should be used. Insect
pins may be purchased in various sizes from a number of biological supply
houses. Size 2 or 3 pins are used for most specimens. Specimens
should be mounted squarely, not at an angle. All specimens should be
mounted at the same distance from the head of the pin. A pinning block
may be used as a spacer to help keep specimens and labels at a uniform height.
Pins are placed in specimens
to avoid hiding or damaging appendages or areas used for identification. The
standard methods for pinning some of the common insects are:
1. Grasshoppers, katydids,
etc.: Pin through the back part of the thorax to the right of the middle
line.
2. Stink bugs and other
large Hemiptera: Pin through the scutellum to the right of the middle
line.
3. Bees, wasps and flies: Pin
through the thorax slightly behind the bases of the forewings and to the
right of the middle line.
4. Beetles: Pin through
the right wing cover near the base.
5. Moths, butterflies,
dragonflies and damselflies: Pin through the middle line of the thorax
at the thickest point, between and slightly behind the bases of the forewings.
6. Small specimens may
be mounted by gluing the specimens to a paper point on a pin.
Relaxing chamber. Many
times it is impossible to pin specimens immediately after they have been
collected and killed. Most of these specimens dry in an awkward or
difficult position to pin. These specimens may be relaxed so that wings
or legs may be moved, even months after they have been collected. To
accomplish this, the insects have to be placed in a relaxing chamber for
a period of time. This allows muscle tissue to absorb enough moisture
to make them elastic.
A relaxing chamber is nothing
more than a sealed container, such as a large jar, containing sand or a similar
media saturated with water. A bit of alcohol may be added to prevent
the growth of fungi. A wire screen or small dish is used to prevent
the specimen from coming into direct contact with the wet media.
Insects are placed in the container
and left until their appendages will move freely. Specimens are then
removed, pinned, spread in the desired shape, and allowed to dry. To
keep the insects from drying out, they can be placed in the freezer for as
many as three days.
Spreading board. Spreading
boards are structures used in spreading the wings and legs of insects and
to hold them in the desired position until they are dry. They may be
made from small pieces of soft pine, cork, balsa wood or styrofoam. Insects
are pinned on the board, spread in the desired position and allowed to dry. Small
specimens dry in one or two days while larger specimens may take several
days.
Preserving in alcohol. Small
soft-bodied insects such as aphids and thrips would soon dry out and shrivel
or become distorted if not preserved in alcohol. Those insects that
should be preserved in alcohol have been listed previously. Many specimens
(especially larvae) turn dark when preserved in alcohol. The smaller
of these specimens may be prevented from turning black by replacing the alcohol
about two to three days after the specimens have been preserved. Killing
and leaving large larvae in boiling water for one to five minutes before
placing them in alcohol may prevent them from turning dark.
Mounting on microscope slides. Only
very small insects such as thrips, lice and aphids are usually mounted on
slides. This technique requires special equipment and a certain amount
of skill. The specimens are placed on the left-hand side of a microscope
slide and a drop of mounting media is added. Then a cover-slip is placed
over the media and specimen. After the mounting media dries, the edges
of the cover-slip are often sealed to prevent absorption of moisture which
may stain the mount. Mounting on slides is an excellent way to preserve
and study small soft-bodied insects.
Labeling specimens. A
proper label greatly increases the value of a specimen. All specimens,
whether pinned, preserved in alcohol, or placed on slides, should be properly
labeled.
A label should contain information
about the location where the specimen was collected, the date collected and
the name of the collector. Labels must be printed in permanent ink,
which is non-soluble in water or alcohol.
Pinned specimens should have
a proper label attached below the specimen. Specimens preserved in
alcohol should have the label inserted into the vial with the specimen, although
many specimens have the label attached to the outside of the vial. Specimens
mounted on slides should have the label glued to the upper side of the slide
and to the right-hand side of the specimen.
4-H
Study Materials - Home | Junior
Study Materials | Intermediate
Study Materials | Senior
Study Materials
Department of Entomology
- TAMU
