The following sample preservation methods are recommended.

Use 95 or 99% alcohol to preserve most field samples. Organic residues will be holding a lot of water. If too dilute of a alcohol/water mixture is used, it will not effectively preserve the sample.

If the sample residue is mostly coarse mineral material, then dilute the alcohol to about 80% with stream water. Coarse, woody organic material will "consume" less alcohol; but fine, leafy material requires a lot of alcohol.

Use copious amounts of alcohol; at least twice the volume of the sample residue.

For best results, let the field-applied alcohol sit in the sample jars for a few hours to a day, then decant off most of the original alcohol, add fresh 80% alcohol, and stir/shake gently.

Be reasonably gentle with the samples, so that invertebrates don't break into pieces. When a large amount of fine organic matter or silt is present (e.g. lentic benthos samples), then make sure the alcohol gets well mixed into the residue. For this sample type, you may want to consider spiking the alcohol with formalin (about 4 cc formalin per liter jar). If you do use formalin, please write "Formalin" on the outside label of the sample jar. Please avoid formalin if at all possible. Represerving the field collected sample with fresh alcohol (as described above) will be adequate in most cases.

Do not allow samples to sit around for long without preserving (especially in direct sunlight). Invertebrates will die and deteriorate very rapidly. Preserve samples shortly after collection. Never leave unpreserved samples out in the hot sun. Also, try to keep preserved samples from sitting in the hot sun for too long.

Some invertebrate groups require special preservation techniques if they are going to be identified to a low taxonomic level or kept as museum specimens.