What is the term for organisms that feed externally on the outside of their host?

The term for organisms that feed externally on the outside of their host is ectoparasites. These organisms live on the surface of their host, deriving nutrients at the host's expense. Common examples include fleas, ticks, and lice, which latch onto the skin or fur of their host and feed on blood or skin.

This term contrasts with endoparasites, which reside within the host's body, often in internal organs or tissues, and could include worms like tapeworms. Symbionts refer to organisms that live in a close relationship with another species, which can be mutually beneficial, harmful, or neutral, but they do not specifically indicate external feeding. Saprophages consume decomposing organic matter, which is also not related to their feeding habits on a host. Understanding these distinctions is essential for properly identifying and managing pests in various contexts, particularly in household pest management.