They're a tiny species with a huge impact on agriculture. And they're sporadically dying off. And no one knows exactly why.
Honeybees are an integral part of almond and, to a lesser extent, prune farming. Bees pollinate both trees. But for the past decade, substantial percentages of colonies have been dying off.
"It varies from year to year. Sometimes you lose 10 percent, sometimes you lose half," said Richard Gordon, who supplies bees to some Yuba-Sutter farmers. "It's a real problem."
The bee decline is not as big of a problem in Yuba-Sutter as it is in areas that grow more almonds (neither walnuts nor rice, the area's top crops, require honeybees), but both almonds and prunes contribute millions to the economy.
There were about 7,000 acres of almond orchards in Yuba-Sutter with a total value of more than $20 million in 2013. There were about 26,000 acres of prunes with a total value of more than $73 million in 2013.
Colony loss dropped off slightly in 2013-14, according to surveys by the Bee Informed Partnership, but there was still a shortage of about 40,000 bees this year, said Randy Oliver, a beekeeper in Grass Valley.
"We're just barely keeping up with almond pollination," Oliver said.
Reasons for the bee decline are complicated and spread across a variety of issues, Oliver said.
One major contributor is the varroa mite, which attacks all lifestages of the honeybee and can pass along viruses.
The mite has also developed resistances to some of the beekeepers' treatments, Oliver said.
Another issue is forage, or, more simply, food.
A shift in agriculture has led to the replacement of open pastures with corn and soybean crops in the Midwest, where many beekeepers move their bees to forage, Oliver said.
"With the herbicide use, there's no weeds out there (with flowers for bees to feed on), so it's become a desert for bee forage," Oliver said. "There's no more food for bees, and it's becoming pretty difficult for the beekeeper."
As a result of declines in forage, beekeepers have to spend more money on feeding bees supplementary proteins and sugars. Consequently, beekeeping has become very expensive, Oliver said.
And that expense has been passed on to the farmers.
The price for a hive of bees used to be around $45 before a major shortage in the winter of 2004. After the shortage, the price jumped up to $155 and has not come down. Today, the price hovers around $170 a hive, Oliver said.
"The bottom line is that it's harder and more expensive to keep bees alive these days," Oliver said.
For almonds, it's recommended that farmers use two colonies per acre, which means there are an estimated 1.6 million colonies in California almond groves, Oliver said.
"It's said that the almond bloom is the single largest pollinating event in the world," said Franz Neiderholdzer, orchard systems advisor for the Yuba-Sutter University of California Cooperative Extension.
The recent drought has also damaged the availability of bee forage, as dry conditions have prevented plants from flowering.
"Water is the new gold," Gordon said. "They need water to cool the hive off, and they need water for flowers to bloom. We're desperate for rain."
But, overall, Oliver said that conscientious beekeepers can ward off high mortality rates with the proper investment.
"The amount of bees that are available are up to the almond growers. If they offer enough money there will be enough bees," Oliver said. "If the growers offered $250 for a hive, there would be a lot of bees."
CONTACT reporter Andrew Creasey at 749-4780 and on Twitter @AD_Creasey.