Scientists Say: Ectoparasite

This is parasite that lives on — not in — another organism

This is a human head louse. It’s a type of parasite that can live on a person’s scalp.

Giles San Martin/Wikimedia Commons (CC BY-SA 2.0)

Ectoparasite (noun, “ECK-to-PAIR-a-site”)

Like a terrible houseguest, a parasite relies on another organism — one it lives on or in — for its nutrients and gives nothing in return. The parasite benefits, while the host usually suffers in some way. Many parasites, such as tapeworms, live inside the host’s body. But ectoparasites are found outside the host. (“Ecto-“ is from the Greek language, and means “outside.”) Examples include a dog’s fleas and the head lice that spread from kid to kid in the classroom.

In a sentence

Lice and fleas that lived on people were ectoparasites that helped spread the infamous Black Death through Europe.

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Bethany is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology from Wake Forest University School of Medicine.

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