Most soil animals are very small. As a result, we don't know much about them. Simple questions like where they live haven't been completely answered. Part of the problem is that larval stages do not look like the adults. Maggots for instance, do not resemble flies. The Tullgren funnel is one method used to separate soil animals from leaves. A light bulb applies heat and light above to leaves, or other materials. Animals moving away from the light bulb are trapped in a vial below. This is a good method for larger animals that can survive the heat. Beetles, springtails and fly larvae are often recovered. Smaller animals frequently dry out and die. Animals trapped in moisture on the sides of the funnel also die.

Soil animals are classified by size. Larger soil animals (macrofauna) include burrowing animals, insects, slugs and snails and earthworms. Middle sized animals (mesofauna) include spring tails (collembolan) and mites. The smallest animals (microfauna) include nematodes.

The most common animals in mushrooms are collembola, fly larvae, beetles, and mites. Millipedes and nematodes are also extracted sometimes.

Earthworms are segmented and larger than most other soil animals. The "nightcrawler" shown here is not native to North America. They dig deep burrows and are very important in decomposition. By mixing soil and organic matter, they have changed the layered structure of some forest soils. I have never isolated one from a mushroom.

Collembola are primitive wingless insects, usually less than 2 mm long. The "spring" under the abdomen and short, thick antennae are distinctive. They have six legs and are white or grey.

The most common fly larvae are white with black heads. They lack legs or antennae. Their bodies are segmented.

Beetles have six legs, antennae, a head and three body segments. They are usually reddish brown or black. Beetle larvae have white, soft, segmented bodies. The six legs are just behind the head. The head is a hard, reddish capsule.

Mites are rarely longer than 1 mm and difficult to see with the naked eye. They are reddish and have eight legs. They do not have the narrow waist between their abdomen and thorax that spiders have.

Millipedes have tube-shaped bodies made up of many segments. Each segment has two pairs of legs (4). The antennae are short. Centipedes in contrast have one pair of legs per body segment.

Nematodes are extremely thin, and range in length from 0.5 to 1.5 mm. They do not have segmented bodies like earthworms. They are transparent (clear).

Among the questions that can be answered using the Tullgren funnel are:

• Do mushrooms contain soil animals?
• Do older mushrooms contain more animals?
• Are different animals found in mushrooms than in leaves?

To get the best results use multiple funnels. By chance one funnel may give a very high number, or a very low number. You can calculate the average by using more than one funnel. You might want to read designing experiments before starting.

Materials for Tullgren Funnel

Ring stand support for Tullgren funnel. Ring stand or other support. 1 ring to hold funnel 6 inch diameter plastic funnel Painter's lamp 25 watt lamp bulb Aluminum foil Masking or duct tape Vial, pill bottle, or small bottle Small piece of window screen
Wood rack for Tullgren funnel. 2 pieces 1 X 6 x 6 inch boards. Drill hole slightly larger than funnel spout in top board. Hole not needed in bottom board, but may help keep vial in place. 1 piece 1 X 2 x 6 inch lumber - left support. 1 piece 1 x 2 x 30 inch lumber - right support.

Materials for Counting Animals:

• Petri dishes or saucers.
• Jar lids.
• Magnifying glass or dissecting microscope.
• Forceps (tweezers).
• Eyedropper.
• Kitchen scale capable of weighing in pounds and ounces, or kilograms and grams.
• Paper plate or plastic storage container to weigh mushrooms.

Procedure:

1. Place one or more mushrooms in a Tullgren Funnel. Place the 25-watt bulb so that the temperature on the surface is about 30°C (86°F). Animals are trapped in 3-4 days. It may take longer if the mushrooms are wet, large, or tough.
2. Pour the contents of the vial into a petri dish, or small saucer. Sort the animals into "species" by using a magnifying glass. Transfer the "species" into jar lids containing a small quantity of 70% ethanol with forceps or eyedropper. Record the number of "species" you collected.
3. Weigh the mushrooms in your funnel, record the weight, then calculate the number of "species" and individual animals per kilogram of mushrooms.

RECORD DATA

• Mushroom plus container weight=______ grams.
• Weight of container for weighing mushrooms=_______ grams.
• Weight of mushrooms minus container ______ grams.
• Total number of animals=___________.
• Total number of "species"=_________.
• Number of "species" per kilogram of mushrooms divided by kilograms of mushrooms minus container weight=______ species per kilogram of mushrooms.
• Number of individuals per kilogram of mushrooms divided by kilograms of mushrooms=_______ animals per kilogram of mushrooms.

You can calculate the average by dividing the total number by the weight of mushrooms in all of the funnels. For example: 500 individuals divided by 5 kilograms=500 ÷ 5=an average of 100 animals per kilogram. Remember you cannot calculate an average from only one funnel.

Further Reading

• MacFadyen, A. 1962. Soil arthropod sampling. Advances in Ecological Research. Volume 1, pages 1-34.
• Nardi, J. B. 2003. The World Beneath Our Feet: A Guide to Life in the Soil. Oxford University Press, USA. 200 pp. ISBN 0195139909.

OTHER EXPERIMENTS

• Moist Chamber
• Yeast in Liquids

Last update: 19 Nov 06. © 2006. Robert Fogel, Ivins, UT 84731.