Flying solo: Some bees got no honey

By Barbara Maynard
Correspondent

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April showers bring May flowers, and May flowers bring ... bees. Honeybees are famous for their powers of pollination, but native bees were doing the job long before European settlers brought hives from Europe.

The elaborate social structure that makes up a honeybee hive is well known: Fertile queens lay eggs, non-fertile female workers feed young, gather food, and construct and defend the hive, and drones (males) exist solely to mate with the queen. Bumblebees have a similar caste system.

In contrast, so-called solitary bees do not live communally or share labor with nest mates. Instead, each female constructs her own nest, and as adults, both males and females take care of feeding themselves.

One species of solitary bee native to Larimer County and most of North America is the orchard mason bee, a relatively small, black bee recognized for its industrious pollination of fruit trees. "There's evidence that a small colony can do just as much pollination as a (honeybee) hive," said Jacob Udel, president of the Northern Colorado Beekeepers Association and keeper of both mason and honeybees.

Mason bees pack their entire active lifespan into a few short weeks in spring and early summer, making them well suited for pollinating spring's first flowers. Udel's colony of mason bees started to emerge on March 23 this year, and by April 10, he figured their active season was winding down. During this short burst of activity, the bees feed and mate, and females find and provision nests, and lay eggs before dying.

Female bees nest in tunnels in soft, rotten wood or stems. Once she has found a suitable spot, the female starts to pack the nest cavity with pollen and nectar, in which she lays a single egg. She then seals off this nest cell with mud, and starts packing food into another cell in front of the first. By the time she's done laying eggs, the tubular nest is a row of individual nest cells, lined up one in front of the other. Eggs destined to become males are at the front of the tube, and future females are in the back. The entrance to the tube is sealed with a thick plug of mud, which presumably prevents birds or parasitic insects from getting to her young.

The eggs hatch a few days after they were laid, and the nearly immobile larvae consume the pollen and nectar left by their mother. After a month of eating, the larvae spin themselves into a cocoon, where they will spend several months in the pupal stage. Around September, the young bees emerge from the cocoon as fully formed adults, which overwinter in their nest cells, awaiting the following spring. Once the days warm up, the bees chew their way through the mud plugs that protected them through their year of development, and begin the cycle anew.

"The males come out first followed by females," Udel said. "Males mate with females as soon as the females emerge, then they die shortly thereafter."

Attracting bees

Insect-lovers can attract mason bees to their gardens by providing nesting sites. Solitary bee houses can be found for sale locally, or they can be made at home by drilling 5/16-inch diameter holes into just about any block of wood large enough to accommodate a 6-inch deep hole. Even though the mason bees are solitary, they tend to nest close to each other, so a cluster of suitable nest sites will be used by a number of different females--but they will not share the same nesting hole.

Another style of mason bee nest available at stores consists of a bunch of 5/16-by-6-inch cardboard tubes lying horizontally in a tin can. Each tube has a paper liner that can be replaced once the inhabitants have cleared out each spring--replacing the liners helps to keep the nest holes fresh and free of parasites after years of use.

Those who shudder at the thought of intentionally attracting bees to the garden should be reassured by the knowledge that solitary bees are much more docile than honeybees are. "You really have to work hard to get stung by one," Udel said. On the rare occasion when a mason bee does sting, the pain is reportedly much milder than a honeybee or yellowjacket sting.

Another solitary bee native to the western United States is the leafcutter, which is about the same size as a honeybee, with light bands on its dark abdomen. Leafcutters are important pollinators for the production of alfalfa seed, and some farmers have semi-domesticated the bees by encouraging them to nest in bee boards, which the farmers then store under the proper conditions to release the bees the following year to coincide with the alfalfa flowering.

While both mason bees and leafcutters are docile and prolific pollinators, they can cause homeowners and gardeners some unease. Leafcutter bees earn their name by lining their nests with pieces of leaves neatly cut from nearby bushes--roses and lilacs are favorites. Homeowners spotting 3/4-inch semicircular pieces cut from the edges of their shrub leaves should realize that the bees don't eat the leaves, and they rarely cut enough to damage the plants. (Technically, mason bees are considered a type of leafcutter bee, too, because they belong to the same family. The mason bees, however, don't cut leaves.)

Homeowners also can become concerned when they see bees flying to and from holes between wooden shingles. If the bees in question are either mason or honeybees, they are unlikely to cause any damage to houses or other structures because these species use soft, rotten wood, rather than excavating their own holes.

Mason and leafcutter bees are only two of several species of solitary bees found locally. Investigating the local bee diversity can be a low-tech proposition: Rather than drilling only 5/16-inch holes in a bee house, try every size drill bit in the toolbox. Some solitary bees don't nest in wood, and some wasps--with mild stings, like the solitary bees--do, so the results are unpredictable.

"I got a little block and drilled all sorts of different sizes of holes from real teeny to just about mason bee size," Udel said. "Last year something was in the real teeny holes--who knows what was in there."