Adapted from the Wisconsin Odonata Survey, written by Bob DuBois
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- Getting Started
A beginning cooperator should start by learning the common species of Odonata in his or her area before doing much collecting. Purchase a field guide or two and a pair of close-focusing binoculars if possible. The initial focus should be to have fun, learn, and just enjoy the process of discovery and exploration! During this process, you can let me know what you’re finding, and you are always welcome to send specimens you have identified to me for confirmation. Once you feel confident about your ability to identify common species, there will be little further need for you to collect them unless vouchers are needed to establish new county records. Vouchers of uncommon species may be needed to establish the existence of breeding sites. Some familiarity with dragonflies before you start collecting will clearly help you to target your efforts toward species and habitats that will contribute the most knowledge, and to avoid taking unneeded specimens. back to top
- The Identification Process
Some dragonflies and damselflies possess sufficiently distinct characteristics to readily allow their identification in the field. These species can be documented with good quality photographs or even sight records in some circumstances. However, even experienced odonatists can identify only about 50% of the species they see without capturing them. Another 20-30% of species can be identified in the field by capturing and examining them live with a hand-held magnifying lens. Specimens that are captured and examined in the field can usually be released unharmed. However, you will find that some species can be identified only by examining them with a microscope. The dichotomous keys and microscopes used for identification are expensive, and much terminology must be learned. The learning curve is gradual because a beginner needs to see lots of specimens to understand the subtle ways that similar species differ. Becoming proficient requires a substantial investment of time, effort, patience, and money. Such an investment is certainly not required for cooperators with MOSP, but if you do make this commitment, you will be well positioned to add significantly to the knowledge of Odonata in Minnesota. Do all that you can to avoid making misidentifications; if you have doubt about the identity of a species, collect the specimen or don’t record it. The easiest approach for many cooperators will be to send me specimens they are having trouble identifying. I will enter verified records into the statewide database, and will temporarily house the specimens in a secure collection I maintain at my home. All specimens will be permanently curated at the University of Minnesota’s Bell Museum. back to top
- What to Sample
Dragonflies and damselflies spend most of their lives as larvae living under water in a variety of aquatic habitats. When ready to mature, they crawl out onto land and emerge from their larval skins (called exuviae) as young adults (called tenerals). This survey samples mature adults, larvae, and exuviae, all of which are at least potentially identifiable to species. Tenerals are soft-bodied, fly weakly, and do not develop full adult coloration until at least a few days after emergence. For this reason, and because they do not preserve well, collecting of tenerals should be minimized. However, the presence of tenerals is important to note because they indicate a breeding site, and their appearance marks the time of emergence of the species.
A rule of thumb is to sample whatever life stage is available, preferring mature adults (easiest to identify) and exuviae if they are present. In some circumstances we may ask you to focus on just one life stage. For example, some clubtails (Gomphidae) are infrequently seen as adults because they have short flight periods and spend much of their short adult life foraging high off the ground or perched in trees. Thus, these species are best sampled as larvae or exuviae. Exuviae have the advantage over adults of firmly indicating a breeding site; adults could have flown to a site from elsewhere. Identification of exuviae can be easier than for larvae because exuviae represent the final and most mature molt of the larval stage where the key larval characters needed for identification are fully developed. Larvae could be at any stage of development, and if only partly grown, may not show the key characters needed for their identification. However, larvae are still very useful and are available over a wider time frame than the other stages.
Males are often more conspicuous than females, and you are likely to encounter many more males than females. In some species, females are very reclusive and are rarely seen. Collecting mostly males is acceptable because they are usually, but certainly not always, easier to identify. Both genders are useful in collections. As you gain experience, we may ask you to focus on one gender or the other with different groups of Odonata. back to top
- How Many to Sample
With mature adults of those species for which specimens are necessary, try to collect a few (two or three) specimens of each. Please note that within some genera, the species are closely related and look very similar. To further complicate the picture, males and females usually differ in appearance, as do tenerals and mature adults. When you learn to identify tenerals, note their occurrence but avoid collecting them unless you have a specific purpose for doing so. When collecting exuviae, an ideal method is to collect all of the exuviae along a measured distance of shoreline, 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. back to top
- When to Sample
June and July are "prime time" for odonates, so your most intense efforts should be concentrated then. However, some species fly later in the summer and fall, often well into October. May is an important month as well, because some species, including some of our rarest ones, have short, early flight periods. A few migratory species arrive in Minnesota as early as mid-April. Regarding time of day, the greatest diversity can often be attained during sunny, warm afternoons. However, some species are most active at other times, so the best time to sample could depend on the species you are looking for. Avoid sampling during inclement weather, as most species perch in trees or other vegetation then and are difficult to find. When collecting exuviae, time your searches to the known emergence periods of the species of interest because exuviae persist only briefly (a week or two) before wind and high water levels displace them. Mid-May through early June is a crucial time frame for collecting clubtail exuviae along rivers and emerald exuviae in bogs. An excellent goal for cooperators is to thoroughly document the diversity of dragonflies and damselflies at one or a few sites near their home. To do so, visit the site at 10-day to two-week intervals during the entire flight period (late April through October). back to top
- Where to Sample
Minnesota has the distinction of being one of the most unstudied states when it comes to Odonates. We have counties with no records of dragonflies or damselflies. Surely, Odonates live in those counties, but no one has recorded any data from them. Since one of the missions of the MOSP is to fill in the distributions of these insects, you are highly encouraged to spend some serious time and effort in those regions.
Other habitats of interest include spring seeps; ephemeral ponds (vernal pools); large rivers; small streams that run through bogs/fens; wooded swamps; acid bog ponds and wetlands with sphagnum mosses; and alkaline wetlands. These areas hold species we need to learn more about, and, due to the difficulty in entering some of these habitats, they have not been as well sampled as some other habitats. Feel free to contact me for help in finding promising areas to sample close to where you live. Presence of sphagnum mosses, in floating mats or with scattered, fishless pools in sedge meadows, are good indicators for a number of rare species of emeralds (Corduliidae). In lakes, diverse shoreline vegetation often provides habitat for many species of Odonata. Some species have very specific habitat requirements, whereas others can be found just about anywhere. Aquatic systems differ in a variety of ways including: waterbody size, water chemistry, presence or absence of sunfishes, and types of emergent and submergent vegetation. Moreover, at any aquatic site there will be a variety of smaller habitat areas that differ subtly from others in shading, shelter from wind, and types of vegetation. So, try to check all habitats present at any site you visit.
Always ask permission before collecting on private lands. Many public lands do not require a special permit, but please check before collecting on those lands. Scientific and Natural Areas (SNA), USFWS preserves, MN State Parks and some other publicly managed lands require a permit before collecting. ASK FIRST! In my experience, the managers of these lands are usually very open to scientific work being conducted on their lands but permission must be obtained, first. Don’t spoil it for the rest of us. back to top
- How to Sample
As you gain experience you can record the presence of those species that you are sure you can identify in the field, and can begin to collect two or three specimens of those species that you can’t identify, especially those you think might be unusual. Feel free to send me specimens at any time to confirm your identifications. Look for subtle differences among species in sizes, shapes, colors, wing patterns, and habits, and visit all the different habitats at a site. Be aware also that species differ in their behaviors, and that these behaviors can vary with time of day and season. Many species fly boldly in plain view, but some are secretive and require patient observation to be located. Sometimes you may be looking for a certain species or group of species at specific sites that I or others have directed you to. Do not collect a species that you know is federally listed as threatened or endangered.
Net dragonflies in flight by swinging at them from behind. Many species will fly a predictable route, so you can watch a while to see the pattern and then set up an ambush at a convenient spot, perhaps where you are partially hidden by a tree or shrub. When perched, approach them with very slow movements. Once in the net, remove the specimen by hand (they don’t bite very hard). If it is a dragonfly, place it by itself, wings held back together, in a glassine or paper envelope along with a date and location label. Close the envelope with a paper clip. Put the envelope into a checkbook box or other similar container. With damselflies, it is easier and cheaper to put 20-30 of them in a tightly sealed jar or vial containing acetone. Alternatively, you can place them into a regular letter-size paper envelope. When they begin flying out faster than you are putting them in, simply write the date/location information in pencil on the outside of the envelope, seal it, and freeze it. Collect all different sizes, shapes and colors of damselflies. back to top
- About Labels
Every biology student is taught that the label is more important than the specimen. Believe it - a specimen with no label is basically worthless. There is nothing more frustrating than having a rare specimen and having no idea where it was collected. Information that must be included on the label is the date, the location, and your name. Locations 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, if you collect a certain species only at a sphagnum-bordered cove at the southeast corner of a lake, then say so. If you visit a lake but stay within a few hundred feet of a public boat ramp, please say so. If you visit an unnamed wetland, pond or stream you should give the Township/Range location from a plat book (or a 7.5 minute quadrangle map) and a physical description (e.g. 200 meters NE of the intersection of Bellwood and After Hours roads). If you don’t have a plat book or a 7.5 minute map, then please make sure that your location description is very clear. The bottom line is that if you find a rare species, you want someone else to be able to read your label and find the spot where you caught it. If you have a GPS unit, include the exact coordinates (latitude and longitude). Please use pencil because pencil marks don’t run when wet or when exposed to acetone. Place labels inside the envelope or jar, not clipped or taped to the outside where they could fall off. back to top
- Preserving Specimens
*See cautionary note about acetone at the end of this section.
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. You need to soak the critters for at least 8 hours (overnight is fine), then allow them to dry before putting them into permanent envelopes. 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, I’m 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. I use an easy to seal, wide-mouth, tupperware-type container for acetoning that is just big enough to hold the sizes of envelopes I’m using. The container holds a pint or two of acetone. 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.
Here's the basic procedure I use. After collecting a dragonfly in the field, I place it into an opaque Odonata envelope then close the envelope with a paper clip and attach a date/location label. I fold the dragonfly’s wings together over the back and slip it on its side into the envelope. I 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. The temporary envelopes used at this stage are cheap and reusable. I prefer end-opening glassine envelopes from Bioquip (www.bioquip.com) and find the 2-3/4 X 4-1/4 inch size most useful. When I get home, I clip the tips of the corners off the envelopes with scissors to allow the acetone in quickly. I submerse the dragonflies in the container of acetone while still in the envelopes. When it is time to dry them the next day, I remove all the envelopes from the acetone jar (using long forceps to keep my fingers dry) and allow them to drip dry for ten or fifteen minutes. Some folks actually make little racks for this purpose (like dish drying racks). I simply prop the envelopes up against jars or some vertical surface over cardboard or a towel to protect the finish of the table I’m working on. After 15 min., I 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. The last step is to put the dry specimens into permanent, clear envelopes with 3 X 5 cards on which the date/location information is written. I fold over the end of the clear envelope and seal with a paper clip. The permanent envelopes are made of either cellulose or polypropylene and are more expensive than the temporary ones. They can be purchased from www.afn.org/~iori/oinstore.html. 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.
Larvae and exuviae are best preserved in 70% 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.
When you have accumulated a good supply of acetoned specimens, let me know and arrangements will be made to get the specimens. You may have to mail them to me. It is possible that I will be heading your way and I could pick them up, but mailing will be the most direct route. When mailing specimens, make sure they are well padded to minimize breakage during shipment. If you think you have collected a rare species, let me know immediately so that after confirming the species, we might be able to make a return visit to the site while the flight period is still occurring.
* 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. 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. When your preserving acetone starts to become yellow and smelly form the dissolved fats, just pour it onto pavement or a gravel road and allow it to evaporate. back to top
- Photographic Records
Photographic records of the common, easy to identify species will be accepted in most cases. A male Twelve-spot Skimmer (Libellula pulchella) is unambiguous and can be easily IDed from a photograph showing the wing patterns. Other species must be photographed from several angles to show the relevant field marks. This may require you to net the insect and to take hand-held photos from a variety of angles. If there is any question as to the identification of the individual in the photo, if it is a rare species, or if it is a significant range extension for that species, a voucher specimen will be required for ultimate acceptance into the database. back to top
- Equipment You May Want
- A big, lightweight aerial net that you can swing quickly (you can make your own or you can buy one commercially from Bioquip Products [see Resources]).
- A supply of paper or glassine envelopes. (I can give you some or purchase your own from the sources listed previously. They cost about eight cents apiece.)
- Acetone (can be purchased at any hardware store; one gallon should last you all year).
- A field guide (cost about $20 - see Resources).
- Field clothing including which may include chest waders, old tennis shoes, wading shoes, hip boots, or at least knee-high boots (depending on the type of habitat). Open-toed sandals are usually not recommended due to the hazards of sharp sticks, rocks or broken glass.
- Pencils, paper, paper clips, scissors.
- A wide-mouth rubbermaid-type or tupperware container capable of holding about 2 pints of acetone.
- Plastic or cardboard containers about the size of a checkbook box for holding your envelopes.
- A sealable, shoe box-size container or large zip-lock bag to hold specimens until I can get them.
- A notebook for recording field notes (optional).
- A carrying bag for hauling all this "stuff".
- Optional but nice - a hand-held thermometer, a quality pair of close-focusing binoculars (ones that focus as close as 4 feet are available) and a quality 16X or 20X hand lens. I have information on purchasing good binoculars. back to top
- Making All of this Simple
- Net it and put it in an envelope with date/location label.
- Acetone it over night then let it drip-dry briefly.
- Put it in a sealable container.
- Hand pick it from a measured length of shoreline or from a bog.
- Put it in any sealable vial or jar with date/location label.
- Add 70% ethanol (or isopropyl alcohol) to jar (best), or leave dry.
- Using any kind of hand/dip net, collect it from the water.
- Put it in a tight-sealing jar or vial with date/location label.
- Add 70% ethanol (or isopropyl alcohol) to jar.
| Adults and tenerals | |
| Exuviae | |
| Larvae | |