Collecting Aquatic "Bugs"

Collecting aquatic insects requires only a limited amount of equipment:

--rubber boots, hip or chest waders
--a long handled net or kitchen sieve
--a shallow white pan
--an assortment of small liquid proof vials and jars
--forceps
--field notebook
--100% to 80% alcohol for preservative
--field bag to carry things such as the vials, forceps, notebook etc.

Other accessories may include:
--special aerial net
--a camera to record pictures of the site
--GPS unit for long/lat info
--thermometer
--fine meshed aquarium net
--turkey baster and/or eye dropper

These supplies can be made or purchased in various forms from retail hardware and drug stores or biological supply companies.

It is wise to go collecting with another person or a group. Not only does this provide a safety factor because slimy rocks are slippery but it also enables the collecting to be done more efficiently. One person can be making general collections with a dip net in the water while the other can be making aerial sweeps of the vegetation, turning over rocks and logs or investigating special microhabitats that may be present.

To make collections in ponds and along lake shores the net is passed through the weeds and open water. In streams and rivers the net can be held downstream of the feet and the feet shuffled to disturb pebbles and small stones. Insects on the stones will fall off and be carried by the current into the net. The net is then swirled in the water to remove fine silt and mud. The contents of the net are then dumped into the pan with about 2 cm of water in it. The insects will be seen crawling out of vegetation, sticks and pebbles and can be easily picked up with forceps or a small net and transferred to a vial or small jar with preservative. Insects can also be collected from submerged logs and stones by hand.

Net sweeps of the shoreline vegetation will collect adults. Sweeps of the water surface with a fine-meshed net will collect exuviae Exuviae are the cast off "skins" left behind after an insect moults from one larval stage to the next or from pupa to adult. of many aquatic insects.

I find one of the most useful collecting tools for shallow water is an ordinary kitchen sieve about 20 cm in diameter. The kitchen sieve can be swept through the vegetation, mud and gravel with no damage. I carry a snap lid 35 mm film canister filled with alcohol and a pair of forceps tied around my neck with a string. I find that I can sweep the net through the water and quickly examine the material collected. When I find interesting specimens I "pop" the film canister lid put them in the alcohol and snap the lid back on.

For each collection location a label written on good paper and in pencil or alcohol proof ink should be made indicating the location, date, and collector's name. Notes about the sample and sample location should also be made in a field notebook for future reference. Photographs of the habitat also provide useful information.

The alcohol should be changed after 24 to 48 hours to ensure the specimens will be thoroughly preserved and not start decomposing. If the jar has a large number of specimens or large specimens in it the alcohol may have to be changed a number of times to ensure proper preservation.

The next step is to sort the specimens into groups and begin to identify and study them. Small vials (2 to 3 drams in size) are ideal for storing sorted insects. (Vacutainer tubes used for collecting blood samples work well.) The sorted insects are preserved in 70% alcohol so they will not become brittle. A label of the location, collection date and name of collector is included in each of the vials with the name of the specimen if it has been identified.

Alcohol is a good all purpose preservative for most aquatic insects, although there are many, some extremely vile, concoctions that have been devised for particular groups. Ethyl alcohol (ethanol) seems to be a better bug preserver than methyl (methanol) or isopropyl (proponal). However, all alcohols cause colours to fade which makes it less than perfect for some groups such as adult dragonflies and damselflies and Lepidoptera. For these groups pinning is a better way of preserving the specimens. The captured specimens are placed in a killing jar (This is an air tight jar that has absorbent material in the bottom with a small amount of ethyl acetate (finger nail polish remover) poured on it.) until they die. An insect pin is placed through the thorax of the insect and the specimen is spread out on a special spreading board until dry. A label is attached to the pinned specimen for reference.

A very worthwhile and rewarding activity is the "rearing" of immature insects. Only a small percentage of aquatic insects in the province can be identified to species in the larval stage so they have to be associated with the adult stage to be identified. For this procedure mature larvae, or pupae, are collected and kept alive in a container of water; (one specimen/container). Rearing containers can be simple plastic beverage cups with a loose fitting lid to elaborate trays with mesh sided cages and aerators to provide oxygen and current to the larvae. Each group of aquatic insects requires different rearing conditions to successfully complete their life cycles. For some groups the larvae may need to be fed. With luck the larva will develop to maturity and the adult insect will emerge. The larval and pupal skins and the adult stage can then be preserved together and become a valuable record of the association as in the image to the left which has the larval and pupal skins along with the reared adult male.

Identifying many aquatic insects can be done with the unaided eye or a simple 10X hand lens. However, for most identifications lower than order or family some form of low powered microscope is very useful. A stereoscopic dissecting microscope capable of magnifications of 7 to 40 times is ideal for this type of work. (Microscopes are also great things to climb and perch on!!!) For most groups no elaborate specimen preparation is needed but other groups require special dissections and mounting on microscope slides to study them under high magnifications with the aid of a compound microscope.

Order and some family level identifications are relatively easy to do with some practise and a good guidebook. However, the majority of genus and species identifications require a great deal of experience and often a substantial library to do with accuracy.