Inside the laboratory.
After discussing the handover arrangents.
Xu Yun turned off the Penguin group chat and began preparing the cockroach bait for practical use.
About half an hour later.
Ding-dong—
Accompanied by a buzz, a WeChat notification sound went off.
Xu Yun picked up his phone, and the sender was Chang Licheng, the class monitor of Applied Physics Class 2.
He hurriedly replied with a quick ’Hold on,’ then grabbed the prepared dicine box and took the elevator down.
Five minutes later, Xu Yun walked out from the main entrance of the dical Center building.
"God Xu! Over here!"
Just as he stepped out, a burly male student rushed up to him.
The boy was around six-foot-one, with a very reliable square-shaped face, and his sparse hairline indicated his grades were likely good.
This was Chang Licheng, the current class monitor of Applied Physics Class 2, ranking in the top three of the departnt academically, a scholarship recipient, but still so distance away from being a ’study god.’
"Licheng is here, thanks for your hard work."
Xu Yun greeted the newcor familiarly and handed over a bottle of mineral water he had brought from the lab:
"Here, have a drink first. I’ll tell you about the specific steps while we’re at it."
Chang Licheng took the mineral water, guzzled down a big mouthful, all the while adopting a listening posture.
Xu Yun first took out a simple reagent, akin to a syringe, from the small box and waved it in front of Chang Licheng:
"What I have here is a newly synthesized cockroach dicine. The specific ingredient is called Imidacloprid, although as soone working in physics you probably won’t understand what that is. Just consider it a special insecticide."
Then he produced a piece of white test paper and squeezed out a rice-sized drop of gel bait:
"Look carefully, just squeezing out this small amount every ti is enough for the cockroach bait; squeezing more would only be wasteful.
Small amounts, multiple tis, these two terms are key."
Chang Licheng nodded, noting the size of the dose, and then asked:
"Got it. But God Xu, should we squeeze this stuff onto specific spots or anywhere?"
Xu Yun quickly shook his head upon hearing this, saying:
"You’ve hit the key point, Licheng. First, carefully recall if you’ve seen any dry, non-sticky, fine grains akin to sand, densely packed, brownish small specks in your dormitory?"
Chang Licheng paused, thought for a few seconds, then his eyes suddenly lit up:
"Hey? When you put it that way... I might have! I spotted quite a few back then in the corner near the dorm’s washing machine, sotis even on the desk. My roommate said it was mouse droppings!"
"That’s feces, alright, but not mouse droppings. It’s cockroach excrent."
As Xu Yun explained, a shadow passed over his eyes:
"Just stick the bait around those black spots first, and you can also apply so at the corners; this is called targeted elimination."
Cockroach droppings are not just simple cockroach excrent.
They are never found individually; each sighting presents a random dense distribution.
Translated into layman’s terms, they are clusters of small black spots, exhibiting a very typical ’densely packed’ effect.
This is because both adult and juvenile cockroaches’ rectal pads can secrete a ’aggregation pheromone’ that is excreted in their feces.
This pheromone sends ssages to nearby cockroaches—inviting them with a call to action, offering a safe place filled with abundant food, and even serves as a al for small cockroaches.
Cockroach feces usually appear in shaded areas of bathrooms, kitchens, and balconies, which is the pri spot for bait placent.
After introducing the bait usage thod, Xu Yun’s remaining instructions covered the minutiae:
"Licheng, let your classmates know when spreading the bait, try to cover the entire floor completely.
Imidacloprid is an insect-specific insecticide; it poses no harm to mammals unless consud twenty vials of bait at once, otherwise, it’s harmless to humans.
Additionally, I added a bittering agent, so even if stray cats or dogs accidentally consud it, they wouldn’t be poisoned."
Chang Licheng jotted down all of Xu Yun’s instructions and then bade farewell, carrying the small box back to the dormitory.
The dormitory for Applied Physics students is in Building 14 of the East District, right next to the donation sanctuary Pogranate Garden, very close to Susu Road, so cockroach appearances are more frequent than in other dormitory buildings.
Before leaving the dormitory, Chang Licheng particularly reminded a few dorm leaders that at least one person must await follow-up notifications in each dormitory.
As a bona fide Liaodong native, Chang Licheng shared the typical righteousness and generosity of most Northeast n. Over the past half year, his character has been unanimously praised by his peers, earning him a good rapport.
Without necessarily rallying an army with a single call, at least his words attract significant attention.
Thanks to his charismatic influence, when he returned to the fourth floor where Class 2 was located, the majority of the dormitories were ready as per his request.
At this mont.
Even Ye Guohong, who had previously gone out with his girlfriend, returned to wait at the entrance of the dormitory hallway.
Upon seeing Chang Licheng arrive, Ye Guohong proactively stepped forward, his gaze pausing on the white small suitcase in Licheng’s hand:
"Hey Old Chang, are you planning to change careers to beco a technician? Ear cleaning or pedicure? Where’s the hand badge for slippers?"
"Get lost!"
Chang Licheng first made an internationally friendly gesture ’凸’ to his buddy, then his expression beca serious and he asked:
"Old Ye, is there anyone in each dorm room?"
Seeing that Chang Licheng got down to business, Ye Guohong stopped joking, pointing to a closed dorm room about seven or eight ters away:
"He Tao and his dorm mates all went to work part-ti, except for them, there’s at least one person in each room."
Chang Licheng nodded slightly; being a weekend, having only one dorm empty was quite an achievent:
"That empty room can be set aside for now. Old Ye, gather the dorm leaders or representatives to co to my room. I’ll brief them on the details."
Ye Guohong, an old partner of Chang Licheng, nodded heavily in agreent:
"Alright, I’ll go find them now."
Five minutes later.
Ye Guohong brought a few dorm leaders to Chang Licheng’s dorm room, but Chang Licheng’s seat was vacant:
"Old Chang, where are you?"
Quickly, a voice echoed from the balcony outside the dormitory:
"I’m here, I’m here, Old Ye, bring everyone over!"
Ye Guohong and the dorm leaders exchanged glances and walked toward the balcony entrance in succession.
At this mont, Chang Licheng was crouched Asian-style on the floor, gazing sideways at the bathroom entrance, lost in thought.
Seeing this, Ye Guohong squinted suspiciously:
"Old Chang, what’s this, trying to be like Old Eight? Not the sa ti, but the sa restroom...?"
"Get lost!"
Chang Licheng waved them off irritably:
"I’m looking at cockroach poop!"
Ye Guohong’s look at him grew even more curious:
"Cockroach poop? Your taste is even heavier than Old Eight’s..."
Chang Licheng responded with a double ’凸凸,’ then called everyone over and relayed the instructions Xu Yun had given him.
Ten minutes later.
All detailed briefings complete.
Each dorm leader had been assigned a syringe of bait and returned to their dormitory to spread it.
Chang Licheng anwhile took out two larger, thicker syringes, handing one to Ye Guohong:
"Old Ye, hold this. Let’s cover the corridor trail, try to finish it within half an hour.
Even though it may not necessarily work, Assistant Xu really helped us a lot, so we should do our part first and leave the rest up to fate!"
Ye Guohong nodded, took the syringe, and followed Chang Licheng to spread the bait.
Forty minutes later.
Inside and outside every dormitory on the entire floor, every hidden corner showing signs of cockroach presence was packed with bait.
Everything was ready, just waiting for the east wind.
.....
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