Pinworm

The human large intestine, specifically the cecum and appendix area; eggs may be found on clothing, bedding, or skin in the perianal area.

They feed on intestinal contents, mucosal cells, and bacteria within the human gut.

Nocturnal migration; gravid females travel to the perianal region at night to deposit thousands of eggs. This often causes intense itching (pruritus ani) which aids in the spread of eggs via the hands.

Risk: Causes enterobiasis, leading to itching, irritability, and sleeplessness. Highly contagious, especially in households or childcare settings. Benefit: None to humans; purely parasitic.