Researchers in Germany have trained honeybees to sniff out drugs, according to a new study, suggesting the insects could someday be good alternatives to police dogs.

After exposing the bees to the scent of heroin accompanied by small electric shocks, the researchers found the insects quickly associated the smell with punishment and exhibited learned “avoidance” behavior, fleeing the source of the odor. They suggest honeybees could one day identify illegal substances in luggage and other contained spaces.

Why do we need drug-detecting bees in the first place? The problem is twofold, says Matthias Schott, coauthor of the study and a biologist, entomologist, and chemical ecologist at Giessen University. 

Training police K-9 units is expensive. According to one cost analysis, the average successful canine police program costs more than $55,000. (That analysis is from 2004, so the cost is likely higher now.) The dog and the handler training alone cost around $14,000, and it can take several years for a dog to be ready to hit the streets. “Dogs also, like humans, need time to rest and cannot concentrate for a long time,” Schott tells mental_floss. “You cannot search a whole airplane with a dog. It’s too much for one dog.”

Secondly, many existing drug-sniffing dogs have been trained to sniff out marijuana. But as marijuana is increasingly legalized, we need dogs to focus on drugs that remain illegal. That's a problem because “it’s not really possible to retrain a dog,” Schott says. “There is a need for freshly trained dogs at the moment, and it takes a long time.”

The ideal alternative drug hunter has good stamina, quick learning skills, and a fantastic sense of smell—and honeybees have all three. That's why Schott put a fake flower on a windowsill in his lab: to lure honeybees for testing. Drawn by an artificial sugar solution, they came—and were trapped. Schott used about 60 in his experiments.

His next step was to find some drugs. Luckily, the Forensic Science Institute of the German state of Hesse and the Police Laboratory for Criminal Technology allowed his team to work with seized heroin, cocaine, amphetamine, and cannabis—but under strict surveillance. “We had to do the experiments at the lab of the police,” Schott says. “We were watched all the time when we did the experiments. It was quite strange.” 

Since honeybees sense smell with their antennae, translating odors into electrical signals, their sensitivity to drugs can be measured by connecting the antennae to electrodes. In the lab, the bees had the strongest antennal response to heroin and cocaine. 

Using negative conditioning (a.k.a. punishment), Schott then trained the bees to sniff out and respond to the smell of heroin. He placed them in a tiny closed chamber about 1 centimeter high and 15 centimeters long that was lined with a metal grid. Because the chamber was so small, the insects were forced to be in contact with the metal at all times. At each end of the chamber were openings where odors were introduced. If the bee was positioned on the left side of the chamber, the odor would come from the left side, and vice versa.

Schott trained the bees to flee from the smell of heroin by introducing a small electric shock each time the drug was pumped into the chamber. As soon as the bee crossed over to the other side of the chamber, fleeing from the scent, the shock stopped. “She will get a shock, but really quickly she learns it and she will run away from it and will not receive more shocks,” Schott says.

After five minutes of conditioning with the heroin odor and a control odor (cis-3-hexenol, “an intense grassy-green odor of freshly cut green grass and leaves”), the bees could take a quick break before being tested again, this time without any electric shock punishment. If the bee still fled the smell of the drug even when there was no electric shock, the learning was complete.

“We observed a significant avoidance reaction when honeybees were presented with the heroin scent after training with heroin as a conditioned stimulus,” the authors write.

The entire process took less than 15 minutes, and then the bees were set free. 

But honeybees are pollinators. They already have a very important job—and they're in trouble. Do they really need to be hunting down drug traffickers? Schott says his study uses a very small sample. “I’m using 60 bees of a beehive, and a beehive has 30,000 bees in the summer, so it doesn’t do them a lot of harm,” he says. Plus, once the bees are trained, they can be used to sniff out illegal substances and then immediately released, none for the worse.

Schott also studies the bee decline and hopes these kinds of studies help raise awareness about their plight.

It’s not likely you’ll see drug-sniffing bees at border control just yet. The current applications are quite limited, since the bees would need to be in small, yet-to-be designed containers: “a suitable device would contain 40 honeybees in behavioral monitoring chambers into which the test scent could be drawn, and avoidance behavior would trigger an ‘alarm’ equivalent to the analogous signal given by sniffer dogs,” according to the study. 

Schott clarifies, “I would put them in a cupboard where you have air sucked in from luggage or something, and the bees are monitored. When they start to flee from that odor, then you know" heroin is present, he says. 

Next he hopes to compare the bees’ newfound narcotic-hunting skills to those of police dogs. “Can the bees perceive what the dog can perceive?” Schott asks. “They don’t have to be better than the dogs. It’s fine if they are just as good as the dogs. I think that would be quite cool.”