Many insects seem harmless at first glance, but some of the facts scientists have uncovered are enough to make anyone uneasy. From creatures that live beneath human skin to insects that can recognize faces, the insect world is filled with strange and unsettling surprises. While most of these creatures play important roles in nature, their habits can be surprisingly disturbing.

One of the creepiest examples is the botfly, whose larvae can develop beneath human skin after being transferred by mosquitoes. Victims may actually feel the larvae moving before they are removed. Cockroaches are no less unsettling—they have been known to feed on eyelashes, hair, and even fingernails while people sleep. Even more shocking, a cockroach can survive for days without its head because it breathes through tiny openings in its body rather than through its mouth.

Mosquitoes may seem small, but they are considered the deadliest animals on Earth because they spread diseases that kill hundreds of thousands of people every year. Giant hornets have powerful stings that can cause severe tissue damage, while bullet ants deliver one of the most painful stings known, often compared to being shot. Fire ants also attack in groups, releasing signals that trigger nearby ants to sting at the same time.

The insects around us may be closer than we realize. Dust mites can number in the millions inside a single mattress, feeding on dead skin while we sleep. Houseflies constantly spread bacteria after landing on waste and decaying matter. Scientists also estimate there are trillions upon trillions of flies worldwide. Perhaps the strangest fact of all is that honeybees can recognize human faces, proving insects are far more intelligent—and mysterious—than many people imagine.