Preserving Specimens

Preserving Adults

The preservative of choice for adult Odonata is acetone because it does a fairly good job of preserving colors, which can be important in identification. Acetoning is not difficult. Soak the insects for 8 hours (overnight is fine), then allow them to dry before putting them into permanent envelopes. If you keep them in acetone for too long specimens can get brittle. The only tricky part is protecting them from dermestid beetle pests shortly after drying. Beetles can get to and destroy recently acetoned dragonflies, even inside your house. If you leave specimens out in the open for days, beetles can infest your specimens and you may not know it. For this reason, be careful not to leave specimens out in the open to dry for more than a few hours. Acetone evaporates so quickly that most specimens will be dry in one or two hours, especially in a warm area such as where the sun is shining through a window. Larger specimens of course take longer to dry than small ones. When in doubt, it is better to have a slightly damp specimen than one infested with pests and not know it. Use an easy to seal, wide-mouth, container for acetoning that is just big enough to hold the sizes of envelopes that you are using. The container should hold a pint or two of acetone. Be careful because acetone can disolve many types of plastic. Polypropylene Plastic (#5) is acetone-proof. Many "Rubbermaid" or "Tupperware" -type containers for home food storage are of this type. 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 or gravel surface on a hot day and it will vaporize almost immediately. Although acetone is considered a relatively safe chemical to work with, it is a good idea to work in a well-ventilated area. Store dried specimens in a similar, air-tight, plastic container to help protect against beetle infestation.

After collecting a dragonfly in the field, place it into a glassine envelope with label information written, in pencil, on the outside of the envelope. Fold the dragonfly’s wings together over the back and slip it on its side into the envelope. Then 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. If you place the specimen container in a cooler or refrigerator, they can stay alive for a frw days. The temporary envelopes used at this stage are cheap and reusable. The 3-3/4 x 5 inch size end-opening glassine envelopes from Bioquip are prefered. When you get home, clip the tips of the corners off the envelopes with scissors to allow the acetone in quickly. Submerse the dragonflies in the container of acetone while still in the envelopes. When it is time to dry them the next day, remove all the envelopes from the acetone jar (using long forceps to keep your fingers dry) and allow them to drip dry for ten or fifteen minutes over cardboard or a towel to prevent the acetone from disolving anything that you do not want destroyed. After 15 min. remove the specimens from the envelopes carefully with soft forceps and lay them on cardboard for a few hours to thoroughly air-dry. The envelopes with the clipped corners are reusable if you erase the penciled on data after recordng it permanently. The last step is to put the dry specimens into permanent, clear 3-1/8 x 6" Odonata envelopes with 3 X 5 label cards on which the date/location information is written. Fold over the end of the clear and seal with a paper clip. Label cards can be printed from the label template and the permanent Odonata envelopes can be purchased from Bioquip. You can then put all your specimens into a sealed plastic container or a shoe box with a few moth balls, and you're done. Once you have the necessary equipment (envelopes, jar, acetone, a pair of soft forceps, index cards, pencil, etc.) it is a simple process and goes pretty quickly. In a pinch you can temporarily freeze specimens as well, 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 very rapidly and colors are usually lost. Back to the top

Specimen Label Template (21 KB pdf). Please print specimen labels from the template document on 65-pound acid-free card stock (like Wausau Bright White Premium Card Stock), available at office supply stores. Write your data on each label in pencil

* Warning *

Acetone is VERY flammable! Although acetone is naturally-occurring in plants and animals (even humans produce small amounts of it) and it is not considered to be very toxic, care should be taken to minimize the inhalation of vapors. Minimize skin contact and AVOID contact with the eyes. Keep all acetone supplies out of the reach of children. Acetone is a primary component in many fingernail polish removers and, not surprisingly, can (and has) removed the finish from tables, countertops, floors, etc. Test plastic containers before using them with acetone as some plastics are dissolved by acetone. Polypropylene Plastic (#5) is acetone-proof. Many "Rubbermaid" and "Tupperware" -type containers for home food storage are of this type.

Collecting and preserving exuvia and nymphs/larvae

Although nymphs and exuvia are a bit trickier to ID (leave the ID to the MDS folks!) the information gained by their collection can be much more valuable than that from adult Odonata. The adults can, and do, fly long distances from their breeding waters. Nymphs can only survive in waters that are suitable for them and they provide very valuable information about breeding habitats.

As always, proper labeling is of tantamount importance! Take proper notes and make labels (written in pencil) while in the field.

Exuvia are the shed exoskeletons that the adults leave behind after they emerge from the water. Since they retain all or most of the characteristic of the nymph, they can be used for ID purposes without sacrificing any live bugs. Dragonfly enthusiasts who are not comfortable with killing anything can collect exuvia, guilt-free, while supplying some very valuable information about the breeding waters of the Odonata.

Collecting exuvia is usually no more difficult than picking berries (although exuvia are not brightly colored). Exuvia are abandoned by the adults at or near the water’s edge and will stay in place until heavy rain, waves or wind knock them down and break them apart.

They can be gently hand-picked into any sort of container. Exuvia are very brittle and care should be taken to handle them as little as possible. For ID purposes legs and antennae can be critical features and they may be of little use if they are mixed together, at the bottom of the jar. Getting the exuvia wet will make it much less brittle while collecting. You can carry them in a container filled with water while in the field.

At your earliest possible convenience, cover the specimens, in a tightly sealed jar or vial, with 80% ethanol. The ethanol softens up the brittle specimens and will preserve them. Fill the jar as full as you can with ethanol, to avoid having the liquid slosh around and damage the specimens. Don’t forget to insert a paper label (Resistall is preferred) and use a pencil or Pigma Micron Pen for writing down the information as the ethanol will dissolve normal ink.

Nymphs/Larvae may be collected with aquatic sampling nets, fish landing nets made with fine mesh, screening, kitchen strainers, etc. Sample in a variety of aquatic habitats: sand, gravel, muck, decaying leaves, riffles, aquatic vegetation, undercut banks, etc.

Samples can be dumped into white pans or shallow tubs for sorting. Place specimens in a container or jar with some damp moss or other vegetation. It is not necessary to immerse them in water and this can actually may be detrimental as the oxygen levels in the water can be quickly depleted and the sloshing action of the water can damage the specimens.

Simple preservation of nymphs in alcohol has been the norm for many years, but in the words of Odonatologist, Ken Tennessen, merely preserving nymphs in alcohol turns them into "little bags of poop". He recommends a hot water treatment first, in order to denature some proteins, allowing for firmer specimens that will be useful far into the future.

Place nymphs into water that is nearly boiling (about 200°F and removed from heat source). Larger nymphs should 'parboil' for 30-40 seconds, smaller nymphs for 15-30 seconds. After they have cooled, daub the excess water off and place in a jar or vials with 80% ethanol, the larvae still contain a lot of water and the alcohol should be replaced after a month or so to reduce the risk of decomposition.

All paper labels (Resistall preferred) should written in pencil or Pigma Micron Pen and inserted into the alcohol. Back to the top

* Warning *

Ethanol is VERY flammable! Use all appropriate cautions and keep alcohol supplies out of the reach of children. There are restrictions on shipping flammable liquids through the Postal Service so the specimens should be hand delivered to the MDS coordinator, perhaps at a workshop.

Dragonfly 101 Dragonfly Biology Dragonfly Behavior Dragonfly Life Cycle Surveying Species of Interest Collecting Specimens Preserving Specimens

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Dragonfly Nymph

Exuviae in Specimen Jar