Why do trucks keep spilling swarms of honeybees onto US highways?

On Tuesday, a truck carrying hives of honeybees overturned on an Oklahoma highway, setting loose swarms of angry insects and trapping a sheriff’s deputy who had responded to the scene in his cruiser.

Surprisingly, bee-related accidents aren’t uncommon on US highways, as trucks regularly transport hives of bees across the country for use by commercial farmers to pollinate their crops. The apparent uptick in bee truck crashes is likely due to an increased number of trucks carrying bees on the road as farmers are hiring beekeepers from afar to fill the void left by losses of local hives in recent years.

Many farmers who harvest crops such as almonds, apples, sunflowers, and grapes have come to depend on renting bees from commercial beekeepers because wind and other physical processes are often ineffective at pollinating the crops.

While there were only 387 beekeeping establishments in the US in 2012, commercial beekeeping is a multi-million dollar business, the US Department of Agriculture noted in a 2014 report. Many beekeepers – who work on a contract basis – live a semi-nomadic lifestyle, often transporting the bees long distances to reach farmers.

Each truckload of bees contains about 400 to 500 hives, with each hive containing a single queen and between 10,000 and 30,000 worker bees. But in the summer, the hives can contain 50,000 to 60,000 worker bees.

Despite several reports of bee-related accidents in the past few years, honeybees are often preferred by beekeepers because they are easier to transport in a densely-packed colony than other potential pollinating creatures, such as bats, wasps, or butterflies.

Beekeepers take particular precautions in transporting the bees, loading them onto trucks at night or before sunrise when they are in their hives and relatively inactive.

The service often comes at a price: beekeepers took in $292.5 million in fees solely for pollinating almond crops alone, the USDA report noted.

During Tuesday’s accident, the inherent risks became particularly apparent, as angry swarms of insects mobbed state highway patrolman Carl Zink, as he responded to a call about an overturned truck on Interstate 35 near Paul’s Valley, Okla., at about 1 p.m., NBC News reported. He was briefly trapped in his cruiser, recording a video as the bees swarmed around the car, although he was only stung once.

It is next to impossible to recapture escaped bees following such an accident. In most cases, emergency personnel have to kill the swarms to prevent them from attacking people. The loss of hundreds of thousands of bees in a single crash frequently ends up being yet another blow to the commercial bee industry, which has suffered extensive losses in recent years due to colony collapse.

Without pollination by commercial honeybees the United States could effectively lose one-third of all its crops, including broccoli, blueberries, cherries, apples, melons, and lettuce.