They’re called lovebugs but nobody seems to love them. In fact, a lot of people in South Korea want them dead.

The thumbnail-size insects began swarming parts of Seoul and nearby cities in mating pairs last month. The infestation is expected to end by this weekend, and lovebugs pose no health risks to humans, so officials have opted for a gentle approach.

Municipal workers are mostly spraying water at them and officials have advised residents to do the same. “Lovebugs are not pests!” the Seoul government says in a promotional video. “Stop using pesticides and protect nature!”

But residents getting caught in the swarms, or scraping layers of lovebug carcasses from their storefronts, can’t understand why Seoul’s most annoying summer insect is getting off so lightly. They want officials to put away the garden hoses and break out the poison.

“There’s nothing beneficial about them,” Ahn Yeon-sik said this week as he hosed down lovebugs from the front of his bar in Incheon, a city neighboring Seoul where officials have also urged the environmentally friendly approach.

Nearby, a man trying to sit on a bench swatted the bugs with a piece of cardboard. A pedestrian ducked swiftly to dodge a pair bearing down on her.

“I’m told they hate water, but it hasn’t worked,” Mr. Ahn said, pausing to bat one away from his neck. He added that he had also doused them with mosquito spray and soju, a popular spirit, to little effect.

The humble lovebug, Plecia longiforceps, pollinates flowers and helps to break down fallen leaves and branches to enrich the soil. It does not bite or carry disease, scientists say.

But because lovebugs are often locked together in their characteristic mating formation, they can appear to be twice their actual size. They also travel in large swarms that can feel unpleasant if you become surrounded.

Seoul had its first known lovebug infestation in 2022 and people in and around the capital are still not used to them. This year, officials in Seoul and Incheon have received thousands of complaints from residents, asking for the insects to be removed from their homes and streets.

Kim Jae-woong, a welder, set off for a hike last weekend at a mountain in Gyeyang, a district of Incheon. He found swarms of lovebugs so thick that they obscured his view and piles of carcasses on the trails. Some bugs even worked their way into his shorts and T-shirt.

“I thought it was bearable at first,” he said. “And then there were dead bugs on the ground and it stank.”

He said he shoveled them by hand to clear the trail for other hikers before trekking back down, shaking the bugs off his body and returning home.

“I heard they were beneficial insects. Why are they called that?” he said. “They have such an unpleasant, repulsive image.”

So far, most officials in Seoul and Incheon have stuck with a water-based approach to lovebug management. Several Seoul districts have urged people to spray them with water and to avoid wearing brightly colored clothing, which could draw their attention. At least one district has rented pump sprayers to residents for free.

But on Tuesday, health officials in Gyeyang caved to the public pressure by activating fumigation trucks. South Korea routinely uses them on mosquitoes, cockroaches and other insects that actually threaten public health.

“We couldn’t handle the volume of complaints,” said Baek Eun-sil, the director of the district’s infectious disease prevention team. “People said they were too disgusting, scary and uncomfortable to live with if we didn’t kill them.”

Even the fumigation didn’t help, said Nam In, who runs a coffee shop there. He said he doubted that officials had any power to fight the infestation.

“They’re just trying to appease us psychologically,” he said as lovebugs crawled on his cafe’s windows and tile floor. “The number of bugs is beyond human control.”

The size of the infestation is anyone’s guess. It seems likely that the bugs entered South Korea on ships that had sailed from eastern China, said Seunggwan Shin, a professor of biology at Seoul National University who studies the insects. Their eggs lie in damp soil and underneath leaves during the winter before emerging in warm weather.

Over the past few summers, they have been limited to the region around the capital, he said. It’s not clear how officials could more effectively deal with them.

Mr. Shin said using pesticides could allow the bugs to develop a resistance, with negative impacts on their predators, such as birds and preying mantises. His research suggests that lovebugs could be lured away with light.

Residents are trying other approaches in the meantime.

One hiker scraped off lovebugs that were clinging to a railing along a trail and collected them in a small plastic bag. He brought them home and put them in his freezer, then made them into a burger patty that he cooked and ate in a YouTube video.

He gave his “loveburger” 4.5 stars out of five.