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Collecting and Preserving Specimens

While it is certainly possible to survey for most odonates without collecting them, there are some circumstances where collection would be helpful. You may want to collect species you cannot identify for later assistance or further inquiry. A very small number of species (or genders of a species) can only be identified by examining them under a microscope, which would require collection. Finally, a voucher specimen may be required to verify an exceptional record, such as a new species found in the state or county. Do not collect a species that you know is federally listed as threatened or endangered. In addition, try to avoid removing individuals from small populations.

Materials Needed for Preserving Adult Specimens

  • Acetone - can be purchased at any hardware store; one or two gallons should last you all year (MSDS sheet)
  • Wide-mouth container capable of holding about one pint of acetone
  • End-opening, 2-3/4" x 4-1/4" glassine envelopes (www.bioquip.com)
  • Polypropylene envelopes (www.iodonata.net/envlopes.htm)
  • Polyethylene baggies
  • Stainless steel and vinyl-covered paper clips
  • Plastic or cardboard containers about the size of a checkbook box or sandwich box for holding specimens in envelopes
  • 3"x5" note cards
  • Label paper
  • Large forceps
  • Soft forceps

Preserving Specimens

The following is a basic preservation procedure for adult odonates: After collecting an odonate in the field, place it into a glassine envelope, close the envelope with a paper clip and attach a date/location label. To place it in the envelope, fold the dragonfly’s wings together over the back and slip it on its side into the envelope. Put the envelope into a sandwich-type plastic container (or checkbook box) for the duration of the field outing along with any other specimens collected that day. Unless it is very hot, they will stay alive for hours (even days) and will pass through all the food waste from their gut, which allows them to preserve better.
When back from the field, clip the tips of the corners off the envelopes with scissors to allow the preservative in quickly. Submerge the dragonflies in a container of acetone while still in the envelopes. Use an easy to seal, wide-mouth Tupperware or Rubbermaid-type container that is just big enough to hold the sizes of envelopes being used. Acetone is preferred because it does a fairly good job of preserving colors, which can be important in identification. Soak the specimens for at least 8 hours (overnight is fine). When it is time to dry them, working in a well-ventilated area, remove all the envelopes from the acetone jar using long forceps to limit skin contact. Allow them to drip-dry for 30 to 60 minutes. Small racks can be made or purchased for this purpose (like small dish drying racks). Then carefully remove the specimens from the envelopes with soft forceps and lay them on cardboard for a few hours to thoroughly air-dry. Dermestid beetle pests can get to and destroy recently acetoned dragonflies, so be careful not to leave specimens out in the open to dry for more than a few hours.
The last step is to put the dry specimens into a polyethylene baggie. Then slide that and a 3"x5" card on which the date/location information is written into a permanent, clear, polypropylene envelopes. This double- bagging technique helps insure the specimen will not be damaged during subsequent removal. Fold over the end of the clear envelope and seal with a paper clip. Finish by putting all of your specimens into a shoe box or similar container with a few moth balls.
In a pinch you can also temporarily freeze specimens, for example to accumulate a larger amount of specimens over time and then go through the acetone routine less frequently. However, freezing is less desirable because when thawed out, the specimens will decompose rapidly and colors are invariably lost.
Acetone removes the lipids from the specimens and turns yellow after considerable use. You can discard old, yellowed acetone by throwing it on an asphalt surface on a hot day and it will vaporize almost immediately. The envelopes with the clipped corners may be reused.
Nymphs and exuviae are best preserved in 70-80% ethanol and placed in vials or small jars, with date/location labels inside the jars. Isopropyl alcohol (rubbing alcohol) is easily purchased at any drug store and can be substituted for ethanol. Exuviae do not absolutely need to be placed in a liquid preservative and can be stored dry. However, they are more vulnerable to breakage when dry and are much more difficult to examine under a microscope.

About Labels

Labels are a crucial part of a collection. A specimen with no label is basically worthless. If you find a rare species, you want someone else to be able to read your label and find the spot where you caught or observed it. To that end, information that must be on the label includes the date, the location, and your name. It is always best to include the exact coordinates (latitude and longitude) as well as a narrative description for locations. Latitude and longitude can be marked in the field if you have a GPS unit or mapping app on your phone, or obtained afterwards with a website like Google Maps. Location descriptions should be as precise as possible and should include not just the name of the lake or stream, but the exact location on it. For example, "a sphagnum-bordered cove at the southeast corner of Clear Lake", or "a few hundred feet west of the public boat ramp on Mud Lake". Be especially descriptive if you visit an unnamed wetland, pond or stream. Use pencil because ink can smear when wet. Place labels inside the envelope or jar of collected specimens, not clipped or taped to the outside where they could fall off.

Making Collection Simple

  1. Net it and put it in an envelope with date/location label.
  2. Acetone it overnight then let it air-dry for several hours.
  3. Put it in a polypropylene or cellulose envelope with date/location information written on a 3x5 index card.
  4. Seal with a paperclip.
  1. Hand-pick it from a measured length of shoreline or from a bog.
  2. Put it in any sealable vial or jar with date/location label.
  3. Add 70-80% ethanol (or isopropyl alcohol) to jar (best), or leave dry.
  1. Using any kind of hand/dip net, collect it from the water.
  2. Put it in a tight-sealing jar or vial with date/location label.
  3. Add 70-80% ethanol (or isopropyl alcohol) to jar.

How Many to Collect?

When collecting mature adults, try to obtain two or three specimens, including a male and female if possible. Note the occurrence of tenerals, but avoid collecting them unless you have a specific purpose for doing so. An ideal method for collecting exuviae is to gather all found along a measured distance of shoreline (100 feet is usually sufficient), looking from the water's edge to several feet up the bank. Note that exuviae could be on the ground or attached to stems of vegetation from an inch or two to quite a few feet above the ground.
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