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Lovable Leeches

Miss Heidi H. Haugen
Access Excellence-Genentech
Adapted from: "Those Amazing Leeches" by Cheryl M. Halton (Dillon Press, Inc.-1989)

Focus Question

"How do you collect and raise leeches?"


Leeches are classified as annelids, or segmented worms. They are related to earthworms and share many traits. They are found in shallow ponds, lakes, and marshes. Some leeches have even been found to live in small desert water holes as well as in antarctic waters. Most leeches live in water; however, some leeches are amphibious. Other leeches are called land leeches and live in moist regions around the world.

Although scientists have found many medicinal applications and uses for leeches, they can be a nuisance. In 1799, soldiers serving under Napoleon marched from Egypt across the Sinai Peninsula to Syria. They drank water from any source they could find, including waters contaminated by leeches. As a result many problems occurred when the leeches attached to the insides of the soldiers noses, mouths, and throats. Once attached, the leeches began to gorge on blood and enlarge. Many of the soldiers died from suffocation due to the enlarged leeches in the air passages. In addition, other soldiers died from excessive blood loss.

Leeches are parasites, that is they live off other organisms without benefiting the host in return.

Where to look for Leeches

Leeches can be found nearly every place there is water. Shallow ponds, lakes, and marshes are popular leech collecting sites. The best time for leech collecting is during the spring and summer. Most leeches are nocturnal and avoid light. Leeches can often be found in shady areas of ponds or in dark places under rocks, logs, and debris of the bottom of lakes.

Collecting leeches

Leeches can be collected by either using a small dip net, or gently with forceps. Many of the leeches you find are probably non-bloodsucking varieties. Most leeches, in fact, feed on small invertebrates such as snails, worms, and insect larvae. There are other leeches that have been found to eat fish & amphibian eggs, and feed on decaying matter at the bottom of their water source. Some of the bloodsucking leeches attach themselves to an organism such as fish and frogs for food.

If you prefer the easy way to look for leeches you can visit or order from your local science supply shop. Both Carolina Biological and Wards carry leeches.

Caring for Leeches

Avoid placing leeches in chlorinated water. Leeches are sensitive to substances such as chlorine, copper, and other chemicals. Water from the collection site, spring water, or dechlorinated tap water is suitable for maintaining an environment for the leeches. Do not used distilled water alone since its extreme purity can be harmful to the leeches' metabolic balance. Keep the water clean and cool. Once the water shows signs of becoming dirty, it should be cleaned. Do not change the water all at once. When changing the water change only 25%-50%. Sudden temperature changes could harm the leeches. In addition, keep leeches out of direct sunlight or artificial light sources because they too can harm the leeches. A 10 gallon aquarium is ideal for a classroom supply of leeches (50max). Be sure to secure a top on the tank-leeches can lengthen their bodies and fit through incredibly small openings. A screen lid can be purchased at most pet stores. Be sure that the lid secures tightly on the aquarium. Filling the tank 75% of the way allows for a barrier in order to prevent leeches from escaping. You can add sand, small rocks, shells, and plants to your aquarium. By adding rocks and other items, your display will look natural and provide places for the leeches to hide.

Feeding your Leeches

Food requirements are different for each type of leech. Leeches do not eat often. They can thrive for months on a single meal. A few live water snails a week would make a great meal. Some of the larger bloodsucking leeches will require a meal from a turtle or frog every month or two. Other bloodsucking leeches can be given earthworms, frog eggs, insect larvae, or even raw ground meat every six-months.


Please answer the following on a separate sheet of paper.
  1. Write a Learning Log on the proper collection and caring methods for leeches.

  2. Why can't you use water directly from the tap for raising leeches?

  3. Where are some locations where you might find leeches? Why?

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