"I hated bedbugs more than anything. However, even in winter, a few bedbugs never stopped appearing in my room. If I had any worry, it would be this hateful worry about bedbugs. I scratched the itchy spot where a bedbug bit me until it bled. It stings. It must be a deep pleasure. I fall soundly asleep."
Yi Sang (1910–1937) wrote this in the short story 'Wings,' published in the magazine 'Jogwang' in 1936, during the Japanese occupation. The author seems to have likened the protagonist, who lives off the money given by a prostitute wife, to a bedbug. However, people today may find it hard to understand Yi Sang's intent. This is because with the development of the economy and improvement in hygiene, few people have seen bedbugs. Many students also do not understand the proverb "burning down the straw-roofed house to catch the bedbug" for the same reason.
However, it's not that bedbugs have gone extinct just because they are not easily visible to us. On the contrary, they are once again thriving recently. They were briefly held back by massive pesticide attacks from humans, but have expanded their activities from slums in underdeveloped countries to glamorous hotels in developed nations, taking advantage of globalization and the era of world travel. Recently, a family of travelers in Korea encountered bedbugs in the bedding, walls, and ceilings of a local hotel, causing a stir. Indeed, it is the heyday of bedbugs.
◇ Humanity's first parasite lurking in ancient cities
Professor Warren Booth of Virginia Tech in the United States explained that bedbugs have always paralleled human history, having lived in caves with bats and then accidentally fallen onto Neanderthals 60,000 years ago. In a paper published in the international journal 'Biology Letters' on the 28th of last month, he noted that while the number of bedbugs living on bats is decreasing, those that have settled on humans are thriving with urbanization.
The research team compared the DNA of 19 bedbugs collected in the Czech Republic. Of these, 9 were bedbugs parasitic on humans, and the rest came from bats. DNA undergoes mutations at a constant rate over time. Therefore, analyzing DNA reveals how many generations have been passed down. The ancestors of the two groups, which emerged from the dinosaur era 100 million years ago, were found to have decreased in number around the last ice age, about 45,000 years ago.
After that, their fortunes were different depending on their hosts. Bedbugs living on bats have continued to decrease in number to this day, but those that transferred to humans saw a dramatic increase in population 8,000 years ago. This coincides with the emergence of agricultural civilization and the appearance of the world's first cities. Çatalhöyük in present-day Turkey had a population of only a few thousand people 9,000 years ago, but the city at Uruk, the center of Mesopotamia, now in present-day Iraq, had a population of 60,000 people 5,000 years ago.
This study suggested that bedbugs might have been humanity’s first and most thriving parasite. Even though fleas from rats later spread the plague bacteria (bacterium) driving humanity to the brink of extinction, bedbugs, despite their repulsive appearance, only pierce the skin for a small amount of blood, causing no more harm than mild annoyance. They chose to grow in tandem with their hosts.
◇ Survived DDT quickly through genetic adaptations
The reason people today are unfamiliar with bedbugs is that they disappeared for a while thanks to DDT (dichloro-diphenyl-trichloroethane), a pesticide used in the 1950s. People thought they had successfully eradicated bedbugs. However, the resilience of bedbugs was stronger than expected. In just five years, they developed resistance to DDT.
Scientists discovered gene mutations bestowing pesticide resistance in nerve cells of German cockroaches and whiteflies. Professor Booth announced last month in the Journal of Medical Entomology that he also found the same mutation in bedbugs. The research team completed preparations to decode the entire genome of the bedbug in 2024, ready to uncover the secret to their resilience.
Coincidentally, bedbugs developed pesticide resistance thanks to companion animals like dogs and cats that live with humans at home. The pesticides effective against bedbugs were banned after the 1990s. Even battling continuously, the enemy had vanished. Instead, there were pesticides used to eliminate fleas on dogs or cats.
Pesticides for pets had similar ingredients to those that once killed bedbugs. As people slept with dogs and cats, opportunities increased for exposure to these pesticides. Bedbugs hiding on humans also gained a chance to develop resistance through this process. The increase of companion animals in urban life provided new avenues for bedbugs.
◇ Spread along with bat guano fertilizer used in agriculture
There have been previous studies tracing the history between bedbugs and humans through DNA. Back in 2019, a research team from the Dresden University of Technology in Germany decoded the DNA of bedbugs collected worldwide to confirm two routes by which bedbugs connected with humans. It was also confirmed that a new species of bedbug appears every 500,000 years.
It was previously believed that bedbugs first parasitized bats 64 million years ago on mammals; however, that timeline was extended back to the dinosaur era, 115 million years ago, by that research. The research team confirmed two routes by which bedbugs transferred to humans. One bedbug which parasitized eagles switched to humans as hosts, and another which lived on bats transferred to humans globally due to increased bat droppings harvesting for use as fertilizer.
In 'Wings' by Yi Sang, the protagonist intended to shout at the end, “Wings, sprout again. Let’s fly. Let’s fly. Let’s fly one more time.” Critics interpreted this as an expression of a strong will towards freedom and hope. As is often the case in reality, not everyone sprouts wings. But let’s not be disappointed. Even without a single wing, bedbugs have thrived for over 100 million years.
References
Biology Letters(2025), DOI: https://doi.org/10.1098/rsbl.2025.0061
Journal of Medical Entomology(2025), DOI: https://doi.org/10.1093/jme/tjaf033
Current Biology(2019), DOI: https://doi.org/10.1016/j.cub.2019.04.048