The main difference between parasites and predators is that the former are organisms that live at the expense of another organism, called the host, while the latter capture and feed on another organism, called the prey. The Australian Museum explains that parasites are generally smaller than their host, whereas predators are typically larger than their prey. Moreover, parasites do not kill their host, but predators often kill their prey.
Although parasites do not kill their host, they harm the host by spreading pathogens, which often affect the host’s metabolism, reproductive activity and behavior. Alison N. P. Stevens, a professor in the Department of Biology at Mount Ida College, states in an article published on Nature Education that scientists classify parasites in two categories. Ectoparasites live and feed outside the body of their host, while endoparasites live inside the host’s body. Plants and animals, both vertebrate and invertebrate, serve as hosts. Examples of ectoparasites are bacteria, fungi, protozoa, ticks and lice. Examples of endoparasites are tapeworms, flukes and protozoa.
Most predators attack in groups to overwhelm their prey. Unlike parasites that only have a single host, predators consume a vast range of animals. In some cases, they eat a large number of prey. For example, lady beetles usually devour hundreds of aphids daily. Other predators target a specific prey group. An example of this are feather-legged assassin bugs that eat ants only. Carnivorous predators include wolves, lions, tigers and hyenas. Predatory invertebrates include centipedes, scorpions, planarian worms, nematodes, and predatory snails and slugs.