What is the most dangerous insect? For us humans, it’s the mosquito, hands down.
Cockroaches do not really fit into the danger category. Some of the approximately 4600 species do carry allergens, and they can carry sickness-causing bacteria, though there’s little evidence linking them to disease outbreaks. Yet when it comes to invoking sheer terror, cockroaches rank pretty high up on the list. Which raises the question, why would such a small animal raise that strong a reaction?
Jeffrey Lockwood is a professor of ecology at the University of Wyoming and the author of The Infested Mind: Why Humans Fear, Loathe, And Love Insects. Lockwood says many of a cockroach’s traits trigger hardwired disgust reflexes. “Fear and disgust are the two universal negative human emotions,” he explains. “One signals immediate danger, and one signals the potential for disease or contamination.” These bugs fit both definitions. “Cockroaches are oily and greasy, which is a real signal for disgust. Also, if you step on one, there’s the crunch—which is disgusting in own right—and that’s accompanied by a whiff of dirty urinal.” This is because they store uric acid in their bodies, a major component of human urine.
On top of that, they move so quickly for their size. One experiment clocked an American roach at nearly 3.5 miles an hour, the equivalent of a human running faster than 200 miles per hour. Add in their propensity to sneak around (not a bad idea when you’re that small) and they have a high startle factor. So they’re very good at pushing all of our fear and disgust buttons.
Yet there’s no real reason to fear them. In fact, they should be admired. Cockroaches were contemporaries with the dinosaurs, and some think if there ever was a widespread nuclear war, they could be the only ones left.
Taken from “You Asked: Why Are Cockroaches So Terrifying?” by Markham Heid (https://time.com/4403068/cockroaches-bugs-insects-fear/?) The illustration came from that site.