Inside the laboratory.

After discussing the handover matters.

Xu Yun closed the penguin group and started preparing combat bait.

After about half an hour.

Ding Dong--

Accompanied by a vibration, a WeChat notification sound rang.

Xu Yun opened his phone, and the sender was Chang Licheng, the class monitor of the Applied Physics 2 class.

He quickly replied with "wait a moment" and picked up the prepared small medicine box and went downstairs.

Five minutes later, Xu Yun walked out of the main gate of the Medical Center building.

"Xu God! Over here!"

As soon as he stepped out, a tall and sturdy boy ran towards her.

The boy was about 1.85 meters tall, with a very reliable square face, and his sparse hairline indicated that his grades must be excellent.

This person is Chang Licheng, the current class monitor of the Applied Physics 2 class, and one of the top three students in the department. He is also a recipient of the department scholarship, but there is still a gap between him and the "academic god".

"Licheng, you're here. Thank you for your hard work."

Xu Yun greeted the person familiarly and handed him a bottle of mineral water that he brought out from the laboratory.

"Here, have some water first. I will also explain the specific operation steps to you."

Chang Licheng took the mineral water and gulped down a big mouthful, while listening attentively.

Xu Yun took out a simple reagent similar to a syringe from the small box and waved it in front of Chang Licheng.

"This is the newly synthesized cockroach poison in my hand. The specific ingredient is called imidacloprid. But as a physics student, you probably won't understand what it is. Just treat it as a highly effective insecticide."

Then he took out a piece of white test paper and squeezed a rice grain-sized bait on it.

"Look, the cockroach poison only needs to be squeezed out in such a small amount each time. Squeezing too much will be a waste. The key is to use a small amount multiple times."

Chang Licheng nodded, noted the dosage, and asked, "I understand. But Xu God, do we need to squeeze it in a specific location? Or can we put it anywhere?"

Xu Yun quickly shook his head and said, "You mentioned the key point, Licheng. First, try to apply the bait near the black spots. You can also apply some in the corners. This is called targeted killing."

Cockroach droppings are not just a simple excretion of cockroaches.

Cockroach droppings do not exist as individual particles. They are always randomly distributed in clusters.

In layman's terms, they are small black dots that appear in clusters, showing a typical "cluster effect".

This is because both the rectal pads of adult cockroaches and nymphs can secrete a "aggregation pheromone" along with their feces.

This pheromone sends a message to the surrounding cockroaches, attracting them with the signal "food is abundant and safe, come quickly", and it also becomes the food for young cockroaches.

Cockroach droppings usually appear in the shady areas of bathrooms, kitchens, and balconies, making them the perfect locations for bait placement.

After introducing the usage of the bait, Xu Yun only had some minor details left:

"Licheng, when you go back, tell your classmates to try to cover the entire floor when placing the bait.

Imidacloprid is a kind of insecticide specifically for insects and is harmless to mammals. Unless you swallow twenty baits in one breath, there won't be any problems for the human body.

I also added a bittering agent to it, so even if stray cats or dogs accidentally eat it, they won't be poisoned."

Chang Licheng carefully noted Xu Yun's instructions, bid farewell to him, and returned to the dormitory with the small box.

The dormitory for the Applied Physics major is in Building 14 of the East District, right next to the donated Shiliu Garden. It is very close to Susong Road, so the frequency of cockroach infestations is higher than in other dormitory buildings.

Before leaving the dormitory, Chang Licheng specifically instructed several dormitory leaders to have at least one person in each dormitory waiting for further instructions.

As a true man from Liaodong, Chang Licheng, like most Northeastern men, is righteous and generous. His character has received unanimous praise from the class over the past year and a half, and he has a great popularity.

Not to mention having a large number of followers, at least people will pay more attention to what he says.

With the blessing of his personal charm, when he returned to the fourth floor where the Applied Physics 2 class was located, most of the dormitories had already prepared according to his requirements.

At this moment.

Even Ye Guohong, who had just gone out with his girlfriend, rushed back and was waiting at the entrance of the dormitory building.

Seeing Chang Licheng, Ye Guohong took the initiative to greet him and his gaze paused on the white suitcase in his hand.

"Oh, Lao Chang, are you planning to change careers and become a technician? Ear cleaning or foot scraping? Where are your slippers and hand cards?"

"Get lost!"

Chang Licheng first made an international friendly gesture of "middle finger" to his best friend, and then his expression became serious as he asked, "Lao Ye, is everyone in each dormitory here?"

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Seeing that Chang Licheng was talking about serious matters, Ye Guohong stopped joking and pointed to a closed dormitory about seven or eight meters away."He Tao and his roommates all went to work part-time, and besides them, there's at least one person in every dorm room."

Chang Licheng nodded slightly. It was the weekend, and it was rare to have a dorm room with no one in it:

"We can ignore the empty dorm for now. Old Ye, you organize it. Call all the dorm leaders or representatives to me, and I'll hand over the details to everyone."

Ye Guohong, who was also Chang Licheng's old partner, nodded heavily:

"Alright, I'll go find them now."

Five minutes later.

Ye Guohong brought several dorm leaders to Chang Licheng's dorm, but there was no one at Chang Licheng's seat:

"Old Chang, where are you?"

Soon, Chang Licheng's voice came from the balcony outside the dorm:

"I'm here, I'm here. Old Ye, bring everyone over to take a look!"

Ye Guohong and the dorm leaders exchanged glances and came to the entrance of the balcony one after another.

At this time, Chang Licheng was squatting on the ground in an Asian squatting posture, looking at the entrance of the bathroom as if in deep thought.

Seeing this, Ye Guohong couldn't help but raise a question mark on his face:

"Old Chang, what are you doing? Planning to imitate Lao Ba? Not at the same time, but in the same toilet...?"

"Get lost!"

Chang Licheng waved his hand at him irritably:

"I'm looking at cockroach droppings!"

Ye Guohong looked at him even more strangely:

"Cockroach droppings? Your taste is even heavier than Lao Ba's..."

Chang Licheng responded with a double 'middle finger' gesture, then called everyone forward and relayed what Xu Yun had told him.

Ten minutes later.

All kinds of details were handed over.

Each dorm leader was given a tube of gel bait injector, and they went back to their dorms to lay down the gel bait.

Chang Licheng took out two larger and thicker injectors, and handed one to Ye Guohong:

"Old Ye, take this. Let's go and smear the tracks in the corridor, and try to get it all done within half an hour.

Although this thing may not necessarily work, Assistant Xu has helped us a lot. Let's do our part first, and leave the rest to fate!"

Ye Guohong nodded, took the injector, and followed Chang Licheng out to lay down the gel bait.

Forty minutes passed.

In all the dorms on the entire floor, wherever there were traces of cockroaches, gel bait was laid.

Everything was ready, just waiting for the right moment.

........

Note:

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