GRAND JUNCTION — Colorado’s first confirmed Africanized honeybees have turned up in a Palisade orchard, stunning entomologists who didn’t believe the bees could survive cold Colorado winters.

The bees, which are much more aggressive than common honeybees, were discovered by an orchard owner who recently was attacked and stung while working on his hives wearing his normal protective gear.

A single bee from the aggressive hive was confirmed to be an Africanized honeybee through genetic testing at Colorado State University. The hive has been destroyed.

“I was stunned by the results of the test. They survived what we considered to be a pretty brutal winter,” said Bob Hammon, a CSU extension agent and entomologist in Grand Junction.

“We don’t understand the significance of that yet.”

Africanized honeybees first turned up in the United States (in Texas) in 1990 after they were introduced into Brazil from Africa.

The bees prefer tropical climates, and it was believed they couldn’t survive in areas with extended winters because they need steady sources of nectar and pollen.

But the bees have slowly been migrating north. The closest they are known to have come to Colorado previously was southern Utah. They have existed there for six or seven years.

Hammon said the bees likely came to Colorado from a Texas queen unknowingly introduced to a local hive by a beekeeper or in the shipping of bees back and forth to California to pollinate almond groves.

The bees are considered a threat to humans and animals when they are in large colonies. Their venom is no more potent than the common European honeybee, but they are much more aggressive and swarms of the bees can deliver multiple stings.

“Bees with an attitude,” Hammon called them.

Africanized honeybees are not distinguishable by sight from common honeybees. They are only microscopically smaller. That size is part of the testing that takes place to determine if they are Africanized bees. Wing and leg segments are measured and mathematically analyzed.

CSU has set up a special laboratory in Fort Collins to test for Africanized honeybees. Beekeepers who suspect they might have Africanized bees can send bees to the lab for genetic testing. Directions for submitting bee samples and the form to include with the bees can be found at wci.colostate.edu.

Nancy Lofholm: 970-256-1957, nlofholm@denverpost.com or twitter.com/nlofholm

Africanized honeybees first turned up in the United States (in Texas) in 1990 after they were introduced into Brazil from Africa. The closest they are known to have come to Colorado previously was southern Utah.