Exercise

Exercise - 1

Exercise: Collection and Preservation of Insects

Equipments
  1. Insect net
  2. killing jar
  3. forceps
  4. relaxing jar
  5. spreading board and pinning block
  6. insect pins and labels
  7. storage box
1. Insect net
There are two basic kinds of nets — aerial nets and sweep nets. The lighter bag on an aerial net is designed to capture insects in flight or at rest. The heavier bag on a sweep net is designed to collect insects in tall grass or shrubs by sweeping or beating through the plants.

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2. Killing jar
Material:
  • Wide-mouth glass jar with a tight lid
  • Absorbent material like cotton, sawdust, or plaster of paris
  • Benzene or ethyl acetate
  • Blotter or cardboard pieces to fit in jar
Place a 1-2 inch layer of absorbent material at the bottom of the jar. Pour in ethyl acetate or benzene and allow it to soak in (when using plaster of paris, do not allow any excess ethyl acetate). Place the blotter or cardboard over the absorbent material (if using plaster of paris, this layer is not necessary). Seal the jar lid tightly. Wrap the lower half of the jar with masking tape to prolong the potency of the killing jar by protecting it from sunlight. When it takes noticeably longer time to kill specimens in your killing jar, recharge the jar by adding more ethyl acetate or benzene.

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3. Forceps
Forceps are used to minimize the risk of damaging specimens whenever you handle insects by hand. Tweezers can be used but are not designed to handle insects and are more likely to accidentally injure specimens than forceps.

4. Relaxing jar
It is best to pin insects soon after they die and while they are still relaxed to minimize breaking any body parts. If this is not possible, dead insects can be softened in a relaxing jar.
A relaxing jar, like a killing jar, is a wide mouth jar (to easily place and remove specimens) having tight lid. Place an absorbent layer (such as sand, cotton, cloth, sponge) in the bottom of the jar. Saturate the material with water and add a little ethyl acetate to inhibit fungus development. Place a protective layer (such as cork, cardboard) over the absorbent material. Place insects that need to be softened on the top layer for some days until they are relaxed.

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5. Spreading board and pinning block
Spreading boards are useful for stretching the wings of insects flat and holding them in place while the specimen dries. A pinning block can be any piece of styrofoam (styrofoam used for packing appliances in boxes, for instance). A pinning block is useful to position legs and other body parts before the insect dries. A pinning block can also be used as a mounting board by cutting a rectangular slit large enough to position an insect’s body and allow the wings to lay flat. Different-sized slits are necessary for different-sized insects.

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6. Insect pins and labels
Insect pins are long, slender pins made specifically for mounting insects. They are available in different sizes varying from 00 – 07, sizes of 2 and 3 are the most useful for general collectors. Small insects should be mounted on cards or pinned with small size (00 size) pins called as minutens.

Labels for pinned specimens should be made on relatively heavy paper. You can purchase blank labels from a biological supply company or you can make your own with unlined index cards or heavy paper. Each label should be approximately 1/2 x 3/4 inch in size or smaller. For neatness, all labels should of same size.

The following information should be included on your labels:
  • Location (state or nearest town)
  • Date of collection (day, month, and year)
  • Name of the collector
  • Environment from which specimen was collected (Host plant, Soil, under light, etc.).
Permanent ink pen or pencil should be used to write on labels. Computer printing is also acceptable. Do not use ball point ink or other nonpermanent ink that can run or smear when wet.
7. Storage boxes
Specimens can be stored in Schmidt boxes or similar insect storage boxes. Cigar boxes and small cardboard boxes can also be used but only for short-term storage because carpet beetles and other scavenging insects can get into these boxes and destroy specimens. Cut a piece of corrugated cardboard or styrofoam of the size of the bottom of the box to make it easier to place the specimens in the box.
Larger collections can be stored in glass-topped display cases.


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Collecting Insects:
Insects can be collected from almost anywhere. The more places you look for, the more types of insects you can find. You can find many insects on their respective host plants. Examine different plant parts depending upon the insect to be collected. Aquatic insects can be found in ponds, lakes, streams, rivers, and bogs and on nearby plants. Watch for insects at different times of the year. Insects are most common during summer, although they can be found outdoors from early spring to late fall. Some may be out only at certain times of the year.
You can increase your chances of finding different insects by using different collecting methods. One common type, known as sweeping, is done by moving a net back and forth through tall plants. This collects a variety of small insects that may otherwise be overlooked.
Another good method for collecting is gathering insects found at night around lights. Black lights are the most attractive. Not all nocturnal insects are attracted to lights so inspect plants and other sites at night.
Once insects are collected, put them in killing jars for several hours. You can also kill insects by putting them in the freezer for one day (some insects may take longer to be killed by freezing). Take them out after they are dead but before they dry out and are rigid.

Pinning Insects:
Rest the specimen on a pinning block and steady the insect by either holding it with your fingers or holding it in place with a forceps. Place the insect pin into the insect body. Insects are generally pinned through the thorax on the right side (Figure 3).

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Approximately 3/8 inch of the pin should be showing above the insect body, enough so you can comfortably hold the pin with little risk of accidentally touching the specimen (Figure 4).

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Once the insect is pinned you can spread the wings by placing it on the spreading board so that the wings are in level with the top of the board. Position the wings where you want them, then use strips of paper anchored by pins to hold the wings down. If it is necessary to position any body parts, place the specimen on a pinning block and use insect pins to maneuver the body part into the position you want.

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Insects too small to pin can be placed on a paper point. Use stiff paper, such as an index card, and cut out to the shape and size shown in Figure 5.

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Place an insect pin through the point on the wide end. The tip of the point can be left as such or bent. Apply a small drop of glue to the tip of the point. Place the insect so the right half of the body is on the point (if the point is left unbent) or place the bent tip against the right side of the body (Figure 5). You may have to hold the insect with forceps until the insect dries enough and won't fall off.



Last modified: Wednesday, 21 December 2011, 11:11 AM