“Honeybees can be trained to detect landmines.”

The system reported here uses two complementary landmine detection methods: passive sampling and active search. [...] Honeybees have emerged in recent years as efficient bioaccumulation and biomonitoring animals.

This capability was exploited using a passive method allowing the honeybees to freely forage in a mined area, where trace explosives present in the environment stuck to the honeybee body, which were subsequently transferred onto an adsorbent material for analysis by a fluorescent polymer sensor.

Honeybees have emerged in recent years as efficient bioaccumulation and biomonitoring animals. Used together, both methods [passive sampling and active search] are anticipated to be useful in an end-to-end process for area surveying, suspected hazardous area reduction, and post-clearing internal and external quality control in humanitarian demining.

Landmines emit a chemical flux over time, and honeybees can collect the trace residues of explosives (as particles or as vapour) on their body hairs. [...] The mined site gave a substantial response in the optical sensor films, with quenching efficiencies of up to 38%.

Sandia chemists are working with entomologists at the University of Montana to see if foraging bees can reliably and inexpensively detect buried mines. One goal of ongoing tests at Montana is to determine which explosives bees can smell and then train them to seek those chemicals. If bees can be trained to associate the odor of explosives (such as TNT) with food (sugar syrup, for instance), the bees may spend more time near plants and surface soils contaminated with TNT, increasing the odds that they would bring back TNT residues from an area that contains buried mines.

Tests were conducted to determine whether conditioned honey bees can be used to locate buried landmines and explosives. [...] U M 's earlier trials had demonstrated that honey bees can be trained to efficiently and accurately locate explosives signatures in the environment.

"The experiment is to condition our bees on the smell of TNT. This scent, it's coming from the TNT. In the centre of this scent, we put the reward. We put sugar solution as a reward to condition the bees that they can find food just in the middle of smell of TNT scent." - Professor Nikola Kezic, Zagreb University.

University of Montana researchers trained honeybees to detect explosives in landmine fields using classical conditioning with sugar rewards for TNT scents. Field tests at Ft. Leonard Wood confirmed detection capabilities.

The current DARPA program extends this work to the training of honeybees to actively search for contaminants such as the explosive residue being released by landmines.

As a result, the bees associate the smell of explosive material with sugar water. That causes them to stick out their tongues that wiggle in the air, looking for nectar. [...] The trained bees are put inside a monitoring device housing a camera to closely watch these buzzing insects’ PER in response to certain materials.

In the early 2000s, DARPA funded research at the University of Montana demonstrating that honeybees could be trained using classical conditioning to detect explosive vapors from landmines in controlled field tests at Fort Leonard Wood, with LIDAR tracking confirming bee localization over mines.

So honey bees can be used to discriminate between minefields and, er, other fields. [Note: The author appears to be cautioning about the distinction between detecting individual mines versus surveying minefield areas.]