What parasite completes its life cycle on or in its host?

• A. Ctenocephalides species
• B. Otodectes species
• C. Hypoderma species
• D. Dermacentor species

Answer: (B)

The key idea is that some parasites complete every stage of their development while attached to or living on the host. Otodectes cynotis, the ear mite, spends its entire life cycle in the ear canal of the host—from egg to larva to nymph to adult. Because all stages occur on the animal, this parasite completes its life cycle on or in its host, which is why it’s the best answer here.

In contrast, fleas begin on the host as adults but need the environment to develop the offspring: eggs fall off the animal, hatch into larvae, then pupate before becoming adults again. Warble flies (Hypoderma) develop as larvae in the host but must leave to pupate in the environment, and ticks (Dermacentor) also spend substantial time off the host between life stages. These patterns mean their life cycles aren’t completed entirely on the host.

So, the parasite that completes its life cycle on or in the host is the ear mite.