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Natural History Collecting Larvae Exuviae (cast larval skins) should also be collected from aquatic plants, rocks, logs and other supports. I prefer to keep exuviae dry and pin them through the base of the wing cases, placing a small drop of white glue at the point where the pin exits the base of the thorax ventrally. It's also useful to preserve a selection in 70% ethanol. Adults Observing patrolling dragonflies before swinging away often pays; positioning yourself in the most advantageous location, especially if it is somewhat concealed, is usually fruitful. Move deliberately. Refrain from waving the net around; keep it as inconspicuous as possible. Swing at fast-flying agile species from behind as they fly by; many will easily dodge a net swung head-on. When an adult specimen is captured, place it alive in a glassine envelope (available in several sizes -- the most versatile is 3.5" x 2.25" -- at stamp collector stores). The wings should be together above the back. In general, put only one specimen in each envelope; they can damage each other. But place pairs caught in tandem or in copula in the same envelope if possible; face them away from each other. If they are too large to go together in a single envelope, make certain that the fact they were mating is indicated on both envelopes. The collection number (cross-referenced to field notes) or full collecting data must be written on the envelope in soft pencil, india ink or other ink that is insoluble in acetone (if the acetone treatment describe below is used). Teneral (recently emerged) adults are fragile and preserve poorly. Place them in paper bags for a day or two so that the cuticle hardens and the colour pattern develops. If collected while emerging, the adult should be placed in a bag and the associated exuviae should be kept and cross- referenced to the adult specimen. Preparation of Adults For convenience, specimens are usually kept alive in the envelopes until the collector returns to base. This also allows time for the specimens to empty their digestive tracts; colour is usually preserved better in a specimen with an empty gut. The colour pattern of some species, especially some blue ones (e.g. Aeshna eremita, A. constricta, A. canadensis) fades soon after capture. This fading can often be reversed by exposing the specimen to sunlight. However, if possible, such species should be treated in acetone immediately. Acetone treatment: Acetone dehydrates the specimen and dissolves fat, reducing the decomposition of colour pigments. Acetone is flammable; use caution. Avoid breathing the fumes and absorbing the liquid through your skin. Acetone can be purchased at most hardware or paint stores. Keep the acetone in a wide-mouth plastic or glass jar or other container inert to the solvent. The wider the mouth, the better. Make sure that the lid is leak-proof. Pack the jar(s) in a box for stability. Acetone is one of those substances that is difficult to carry on scheduled airline flights. Sometimes it is best to get it after you arrive at your destination. Try to take along the necessary jars or containers, though. It is normally harder to find a good jar with the right dimensions than it is to find acetone. The dragonfly must be killed and its body arranged in the proper configuration before treating it in acetone, otherwise it may dry with abdomen curled and wings and legs awry. I prefer to do this by placing a few drops of my usual insect killing agent, ethyl acetate, in the envelope containing the specimen. As soon as the insect is dead, the abdomen should be straightened (to make measuring it easier) and the legs should be brought forward (so that they do not obscure the base of the abdomen). The envelope containing the dragonfly then is immersed, on edge, in the acetone. If ethyl acetate is not available, the envelope and dragonfly can be placed in the acetone, killing the dragonfly. However, if this is done, you will have to remove the envelope from the jar after a minute or so; straighten the abdomen before replacing the envelope in the acetone. This method is a bit messier and subjects you to more acetone exposure, which is best avoided. Some collectors kill dragonflies, especially larger species, by injecting acetone into the thorax and base of abdomen with a hypodermic needle. This introduces the chemical into the muscles and organs faster than simple soaking, and some swear that it improves colour retention. Leave the dragonflies in the acetone for about 24 hours. The usual procedure is to take the envelopes out for drying when the next day's catch is ready to go into the jar(s). The acetone should be replaced after a few batches have been processed, i.e. when it becomes pale yellow (indicating considerable dissolved fat). Drain the acetone out of the envelopes back into the jar (some collectors snip a little bit off the bottom corners of the envelopes to facilitate drainage) and dry them and the specimens in them in a well-ventilated place. When possible, I do this outside in the sun and breeze. When the envelopes are very dry, store them in Tupperware or cardboard boxes that will withstand crushing. Store the envelopes vertically, like a card file, and DO NOT pack them tightly. At this stage specimens can be squeezed and flattened if jammmed too closely together. Tupperware containers are good because their tight seal prevents most pests from attacking your specimens. In humid climates, the inclusion of silica gel dessicating packets helps keep the specimens dry. Specimens can be shipped by mail safely and efficiently in the glassine envelopes. Simply make certain they will not shift or slide around in the container (pack with tissue if necessary) and nest the box in a larger box, protected on all sides by three or four inches of packing material. If using acetone is impossible, simply dry the specimens as rapidly as possible after they have been killed. Placing the boxes containing specimen envelopes at close range over or under electric lights is helpful. Or put them on the dashboard of your car in the sun. The faster the drying occurs, the better the colour preservation. In the tropics, acetone is invaluable, since air-drying specimens is difficult and specimen damage is common. Acetoned dragonflies may even resist damage by pests (ants, carpet beetles, psocids, mice) more than untreated ones. Another alternative is storage in 70-80% ethanol, either in envelopes or without them. If envelopes are not used, specimens may later be removed from the alcohol and dried in envelopes in the correct position. Most collectors consider both air drying and alcohol storage less desirable than the acetone treatment. Permanent Storage Additional Information Rob Cannings, Curator of Entomology
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