Collecting Aquatic Insects

At some point many fly fishers decide to keep a record of the hatches and major types of insects they encounter on their streams or lakes – in other words an insect collection. Some basic planning upfront can make this a valuable and fascinating activity rather than a waste of time.

            Remember when you where eight or nine years old? Remember how your backyard was full of strange creatures you tried to catch, and when successful went to see how high your mom would jump when you dropped your prize on the kitchen table? Remember how exciting it felt to hold something strange up close and really look at it and wonder what it might be like to be a snake or a lizard or a butterfly? For many kids this fascination turned into an insect (usually butterfly) collection that unfortunately too often got relegated to the bottom of a closet where it slowly decomposed. Now you are a fly fisher. And like the eight-year-old you once were you are again trying to get a close look at strange creatures, and wonder, “What size and color is this little @@**##; what fly will imitate it?” You might also be thinking about starting another insect collection so you can bring that frustrating little @@**## home, find out just what it is, and come up with a fly pattern that will work when you see fish taking it again. Beware. Remember that decomposed butterfly collection? This time start with a plan. 

There are three major issues to consider for collecting and maintaining an aquatic insect collection: 

1.     What techniques to use for collecting specimens from a stream or lake.

2.     How to preserve specimens correctly so they will last for decades.

3.     How to organize your collection so you will know what you have and be able to find specimens when you want them.

Field Collecting Tactics

            The collecting approach you use will depend partly on your purpose for collecting and how detailed you want to be. But before you even start you need to make sure it is legal. Some states have laws that require anyone collecting aquatic organisms, even insects, to have a collecting permit. State fish and game departments typically manage such permits, and the rules are usually in place to prevent the spread of invasive species and regulate commercial collecting of species for bait. Important concerns for sure. While I have never heard of a fly fisher getting pinched for picking up some rocks and looking at the insects on them, you should check existing state game laws to see what’s allowed and what isn’t.

            If your main purpose is to collect a few specimens of the insects flying around the water that fish seem to be eating, then all you need is something to grab them out of the air with. A big hat will work in a pinch. Better is a small net, like an aquarium net, that you can keep tucked in your vest. Better yet is a large net, such as a butterfly net. The downside is that this is more than most anglers want to carry while fishing. If you want to see what fish might be feeding on underwater you will need to take a different collecting approach.

            The simplest method of collecting insects from a stream or lake bottom is to just pick up some moderately sized rocks from a medium to fast riffle, or chunks of wood or small logs submerged near the lakeshore. If no rocks or wood are present then look for aquatic plants or plant debris, like decomposing leaves. Lift the pieces of substrate carefully as many insect nymphs or larvae will let go when they sense their home is mysteriously rising out of the water. Once you have a rock or log in hand you can check it carefully for different types of insect larvae and even see if pupae are attached. This can give you some good clues about what fly patterns to try. If you want to get a better look at the bugs on the rocks drop them into a small white tray (a white mason jar lid also works well) with a half-inch of water. Once in the water against a white background, you will be able to clearly see their color and how they move. You can also drop your prospective fly pattern into the water next to them, and see exactly how close in size and appearance your fly really is: instructive, but also quite humbling. 

            The fact that many insects fall off or let go when you lift substrate from the water means you don’t get a very complete picture of what is really there. A more effective approach in streams is to hold some type of net against the bottom, perpendicular to the current, while you or a friend disturbs the substrate upstream of the net. The current carries any dislodged insects into the net, which you can then lift from the water and check what critters are crawling on it. Again medium to fast riffles, six inches to two-feet deep, are great places to sample. It is best to take four or five kicks from different areas in the riffle. Take one from a shallow, slow area near shore, another further out in faster water with larger substrate, and the others from areas with slightly different current speed and bottom type. After each kick remove the major types of insects from the net and place them in a white try or jar lid with water. A pair of light tweezers will make capturing and handling the insects much easier. Some of the types of collecting nets available include:

·      A fine-mesh net cover for your landing net. These work great for capturing emerging or adult insects drifting in the surface film, but they do not work so well for gathering insects off the bottom.

·      Small collapsible or folding kick nets. Many fly shops carry collapsible kick nets that fold down to a size that fits in your vest, but are large enough to take a good sample. A good choice for many situations.

·      Noncollapsible kick nets. A larger kick net can be made easily at home from fiberglass window screen and two, four-foot, one-inch-diameter wooden dowels. Attach a three-foot square of window screen to the dowels and you are set. Works great, but is bulky to carry.

·      D-frame aquatic sampling net. These are commercially available nets made with a D-shaped metal hoop with fine-meshed net bag attached to a five-foot wooden or metal handle. I have found one sold by Wards Scientific (www.wardsci.com) for about $50 to be very good. The nice thing with this net is that it can be used effectively in streams and lakes, though you probably won’t want to carry something this size while wading a stream.

Besides tweezers and a white lid or tray, it is helpful to have a small hand lens. A 10x to 15x magnifying glass or jeweler’s loupe, will help you see whether those wingpads really are well developed or not.

            Last, consider how your collecting might impact the stream or lake. In most healthy trout waters disturbing a few square feet of bottom will have no impact on the insects or fish. Of course if dozens and dozens of anglers are collecting from the same general area day after day, it is a different story. As with most things moderation is always best. Also avoid taking samples where and when trout or other fish may have recently spawned, or from areas with sensitive plant communities growing on the bottom. Basically, if in doubt, keep your net out. After you have finished looking at the insects, only keep a few for your collection and return the rest to the stream or lake unharmed. 

Preserving Your Specimens

            Keeping a few specimens from your collecting activities will have no detrimental effects on the insect population, and can be very interesting when you get them home and take a really close look at them. Up close you can find out what they are, read about their behavior and habits, and fine-tune some patterns to match them. But if you want them to stay in good condition and be useful for years, even decades, you need to preserve and store them correctly. Fortunately, this is easy to do.

            If you had a butterfly or other insect collection as a kid, you will remember how your specimens were speared onto special pins and stuck in a wooden or cardboard box. Pinning aquatic insects does not work. The reason is that when aquatic insects – nymphs, pupae, or adults – are exposed to the air for even a few hours they shrivel up into unrecognizable little blobs. Therefore, all stages of aquatic insects must be stored in a liquid preservative. The best preservative in my opinion is 85 to 90% (percent, not proof) ethyl alcohol. Yes, that’s good old grain alcohol, so you can imagine just how pickled these critters end up. But you don’t have to use drinkable alcohol. I usually buy 90% denatured ethanol at a drug store or chemical supply company. Denatured ethanol is treated with other chemicals that make it quite undrinkable. If you can’t get ethanol you can use isopropyl or rubbing alcohol, as well. However, isopropyl alcohol causes specimens to get brittle so that legs or tails easily break off. Other chemical solutions have been concocted to preserve insects without changing colors, as alcohol will fade or slightly alter the color of many specimens. These solutions, however, often use more toxic chemicals like formaldehyde, so I don’t mess with them.           

            You will also need something to put your specimens and alcohol into that stays completely sealed so the alcohol won’t evaporate over time: A not so easy problem to avoid with alcohol. Many commercial bug collecting kits sold in fly shops come with small screw-cap glass vials. Nearly all these screw-cap vials don’t seal well enough. It may take one or two years, but eventually the alcohol evaporates and your nice mayfly nymph ends up looking like King Tut’s little finger. For years I have used one-dram glass shell vials with plastic snap-on lids sold by the Kimble glass company (Kimble product # 60965D-1). They are easier to use than screw-cap vials and they seal so tight that vials I have had for over 15 years show no loss of alcohol and the specimens inside look in much better shape than I do.  

Keeping Your Collection Organized

            Many people loose energy or get lazy at this stage and skip this part. Bad idea. Collecting bugs is fun, taking some home to look at up close is cool, spending time labeling vials, recording where and when they were collected, and keeping it organized is work. It’s this work however that keeps your collection out of the closet and will make it a valuable resource of information that becomes more valuable with each passing year. If you start a collection don’t skip these next three steps.

1.     Label all vials correctly. The simplest label I’ve found is a piece of heavy weight white paper cut small enough to just fit inside the sample vial. Putting the label inside the vial prevents it from ever falling off the vial as often happens when labels are attached to the outside. Because the label is in the alcohol the best tool to write with is a #2 lead pencil. It’s cheap and pencil never fades or bleeds in the alcohol. On one side of the label put the date the specimen was collected, where it was collected (state, county, lake or stream name, a short location description, and who collected it). On the other side write the name of the specimen and who identified it. Common names are fine, but include scientific name if you know it. Do not include guesses on the label. 

Example Label:

Side 1:            15 April 2008, Lane Co., OR

                       Beaver, Cr., rivermile 11

                        Coll. Rick Hafele

Side 2:            March Brown Mayfly

                        Rhithrogena morrisoni

                        ID. Rick Hafele

Always label your vials BEFORE you leave the stream or lake for home. It is amazing how one forgets where certain specimens were collected once you pull into your driveway.

2.     Record where and when each vial was collected and what is stored in the vial. This can be done in a notebook or computer spreadsheet. The nice thing about a computer spreadsheet is that once set up you can search your spreadsheet for specific information: All the stoneflies collected in April, for example. The level of information you record is up to you, but at a minimum include a vial number (this number needs to be on the vial also) so you can find a specific vial quickly, specimen name, and where and when it was collected. Including information about the weather, fish feeding activity, and effective patterns turns this notebook or spreadsheet into an excellent fishing log.

3.     Build or buy some type of storage cabinet for your collection. It won’t take long before you have dozens if not hundreds of vials with insect samples from many different locations. A small cabinet to store your collection not only adds to its visual appeal, but also reduces potential complaints from less buggy people in your house. 

With a little effort your collection can escape the closet and become a useful tool and valuable record that might even spark the curiosity of others, perhaps your own kids or grandkids, and start another generation of fish people.

 Just the Facts:

·      An insect collection isn’t for everyone, but if you’re interested start off right. 

·      Check local and state game laws for what collecting is allowed and what permit if any is required.

·      The basic equipment needed includes: Collecting net (small collapsible net best), small white tray or jar lid, tweezers, hand lens, and vials and alcohol.

·      Number and label all vials immediately.

·      Create a notebook or computer spreadsheet for recording detailed information about the contents of each vial and where and when the specimens were collected.

·      Find a small cabinet to store your vials in. 

·      More information about aquatic insect collecting can be found on the web.