Wisconsin Odonata Survey

Back

Guidelines for Sampling Odonata
from Robert DuBois



Getting Started


A beginning cooperator should start by learning the common species of Odonata in his/her area before doing much surveying. 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, visiting the Wisconsin Dragonfly Society (WDS) facebook group page is likely to be helpful and encouraging. There you can post your photographs to confirm your identifications, ask questions, and learn about coming WDS activities. Further, feel free to let me know what you’re finding (robert.dubois@wisconsin.gov), and you are always welcome to send photographs and even specimens you have identified for confirmation.

The Identification Process


Most dragonflies and damselflies possess sufficiently distinct characteristics to readily allow their identification in the field. Important characteristics to notice include colors, patterns, sizes, shapes, and even behaviors. The many "easy" species can be readily documented with good quality photographs or even sight records in many circumstances (see section on acceptance of records). However, even experienced odonatists cannot identify all of the species they see without capturing them. Of these "tougher" species requiring capture, most can be identified in the field by netting them and examining them live with a hand-held magnifying lens (10X loupe). Specimens that are captured and examined in the field can usually be released unharmed.

However, for a beginning cooperator to get to this level of proficiency, a significant learning curve is involved. The learning process is definitely eased by netting lots of specimens and examining their appropriate structural parts with a hand lens and comparing what you see with the illustrations in a good field guide. The learning curve is gradual because a beginner needs to see lots of specimens to understand the subtle ways that similar species differ. You will soon notice that within a number of 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. So even though we have "only" 164 known species of odonates in Wisconsin, there are more than twice that many "looks" you will eventually become familiar with.

Becoming proficient requires a substantial investment of time, effort, and patience. Everyone I know who has made this investment would agree that it was entirely worthwhile, both in terms of their own personal enjoyment and in their ability to contribute knowledge that will help to conserve and protect dragonflies. Obviously, the harder any of us works to hone our identification skills, the better positioned we will be to add significantly to the scientific knowledge about the Odonata of Wisconsin.

A very small number of species (or genders of a species) can only be identified by examining them under a microscope. The dichotomous keys and microscopes used for the most difficult identifications are expensive, and much terminology must be learned. For most people, this level of commitment is superfluous and they focus on those species and genders that they can reasonably identify. Any level of cooperator investment in learning to identify odonates is appreciated by the leaders of WOS and WDS. We simply ask that you do all that you can to avoid making misidentifications. If you have doubts about the identity of a species, take multiple photographs to show to others, or even collect the specimen. If doubts remain, don't record it.

We will enter all verified records submitted through WOS into a statewide database that is used to provide information to support rarity status assessments and give management guidance for property protection. All specimens sent to us will be housed in a secure collection maintained at the WDNR Superior Service Center. Vouchers of rare species will be shipped to appropriate museums or university collections.

What to Sample


Dragonflies and damselflies spend most of their lives as nymphs living under water in a variety of aquatic habitats. When ready to mature, they crawl out onto land and emerge from their nymphal skins (called exuviae) as young adults (called tenerals). This survey samples all stages: mature adults, nymphs, 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 hours or 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 their presence indicates a nearby 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) if they are present. In some cases it may make sense 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 far from shore over water or perched in trees. Thus, these species are best sampled as nymphs or exuviae. Exuviae have the advantage over adults of firmly indicating a breeding site; adults could have flown to a site from a considerable distance. Identification of exuviae can be easier than for nymphs because exuviae represent the final and most mature molt of the nymph stage where the key characters needed for identification are fully developed. Nymphs could be at any stage of development, and if only partly grown, may not show the key characters needed for their identification. However, nymphs are extremely useful, especially when mature, 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.

When Collecting, How Many is Enough?


With mature adults of those species and circumstances for which specimens are necessary, try to collect a few (two or three) specimens, including a male and female if possible. Regarding tenerals, it is best to 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 (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.

When to Survey


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 Wisconsin as early as mid-April. Regarding time of day, the greatest diversity can often be seen during sunny, warm afternoons. However, some species are most active at other times, so the best time to survey could depend on the species you are looking for. Avoid surveying 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 in large numbers only briefly (a few weeks at most) before wind and high water levels displace them. Mid-May through mid-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. If this is your goal, visit the site at 10-day to two-week intervals during the entire flight period (late April through October).

Where to Survey


The habitats of focus in recent years have included 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; coastal wetlands; and alkaline wetlands. These areas hold species we need to learn more about, and they have not been as well sampled as some other habitats. 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 your site. Feel free to contact me for help in finding promising areas to sample close to where you live.

How to Survey


The goal of surveying should be to gain as complete a picture as possible of the species that occur at a site. Depending on season, one or more life stages may be present (adults, nymphs, or exuviae). For adults, as you gain experience you should record the presence of those species that you are sure you can identify in the field, and photograph or collect specimens of those species that you can't identify. Look for subtle differences among species in sizes, shapes, colors, wing patterns, and habits. Make liberal use of your field guides to confirm identifications. 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, weather conditions, and season. Many species fly boldly in plain view, but some are secretive and require patient observation to be located. Do not collect a species that you know is federally listed as threatened or endangered.

Net dragonflies while 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 odonates are perched, approach them with very slow movements, then when you are close enough, swing fast. Once in the net, remove the specimen by the wings holding them together over their back (they don’t bite very hard). Examine it with your hand lens at the appropriate angle to see structures as they are illustrated in your field guide. If you are collecting a specimen, 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, small sandwich box, or other similar container. Watch the instructional videos on collecting and preserving specimens located on this website.

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. For locations, it is always best to include the exact coordinates (latitude and longitude). This can be marked in the field if you have a GPS unit, or done online with a mapping program (like Google earth or Acme Mapper). 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, 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 latitude/longitude coordinates or 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 GPS unit, online mapping capability, 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 or observed it. Please use pencil because pencil marks don't run when wet. With collected specimens, place labels inside the envelope or jar, not clipped or taped to the outside where they could fall off.

Preserving Specimens


An instructional video on this topic can be found below. 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 (obtain an MSDS sheet containing safety and fire hazard information associated with use of acetone). Acetoning is not difficult. You need to soak the specimens 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. I use an easy to seal, wide-mouth Tupperware or Rubbermaid-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 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 and limit contact with your skin.

Here's the basic preservation procedure used by Bob DuBois: After collecting an odonate 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. To place it in the envelope, 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 to the lab, 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 30 to 60 minutes. Small racks can be made or purchased for this purpose (like small dish drying racks). I then 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 http://www.iodonata.net/. I actually prefer a double-bagging technique (see instructional video below). You can then put all your specimens into a shoe box or similar container 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 invariably lost.

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.

Equipment You May Want


  1. A digital camera with strong macro-photography capabilities.
  2. A quality pair of close-focusing binoculars.
  3. A lightweight aerial net that you can swing quickly (you can make your own or you can buy one commercially from BioQuip Products [see Resources]).
  4. A quality hand lens (loupe). Many odonatists use a 10X loupe like the Belomo triplett.
  5. Knee-high rubber boots, hip boots, or waders (depending on water depth where you intend to go).
  6. A supply of paper or glassine envelopes.
  7. Acetone (can be purchased at any hardware store; one or two gallons should last you all year).
  8. Field guides for dragonflies and damselflies (cost about $20 - see Resources).
  9. Field clothing and insect repellent as appropriate.
  10. Pencils, paper, paper clips, scissors.
  11. A wide-mouth container capable of holding about one pint of acetone.
  12. Plastic or cardboard containers about the size of a checkbook box or sandwich box for holding specimens in envelopes.
  13. A notebook for recording field notes (optional).
  14. A carrying bag for hauling all this "stuff".

Making Collecting Simple


Adults
  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.

Exuviae
  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.

Nymphs
  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.

 


This site is produced in conjunction with the Wisconsin Aquatic and Terrestrial Resources Inventory and sponsored by the Wisconsin Department of Natural Resources. The information presented on this site is subject to the Wisconsin Department of Natural Resources' Legal Notices, Disclaimers, and Terms of Use.