With all the talk about honey bee nutrition lately, just how much food does a honey bee colony need and how far can the workers fly to find find it?

"A healthy honey bee colony requires approximately 50 pounds of pollens and 100 pounds of honey to survive for 12 months," says Extension apiculturist Eric Mussen of the UC Davis Department of Entomology and Nematology, who will speak at both the Western Apicultural Society Conference and the California State Beekeepers' Conference this fall.

"Honey production exceeding 100 pounds may be harvested as a honey crop," he says. "From spring until late fall the adult honey bee population turns over at a rate varying from an initial high of around 2000 bees a day to 1000 in the summer, and to 0 in areas with real winter."

During the peak season, a queen bee can lay 2000 eggs a day. That's a lot of mouths for the nurse bees to feed. They need food, and lots of it.

"In order to meet the nectar and pollen demands to feed all that brood (immature bees) each colony has to have an acre-equivalent of honey bee-attractive bloom within foraging flight range," Mussen says. That's up to four miles from the hive and covers a 50-square mile area.

The foraging field force of a honey bee colony, he says, usually consists of one-third of the total population.  Some 40,000 to 50,000 bees comprise a colony during the peak season. The foraging population is subdivided into groups of bees specializing in collecting water, nectar or honeydew, pollen, or propolis (plant resin).

That's a lot of work for the foragers.

Here's how the numbers roll.

Statistics show that California has a total land mass of 104,765,440 acres. Of that, fresh water covers 4,949,760 acres. "The remaining 99,815,680 acres are solid ground," Mussen says.

"Our best estimate is that California beekeepers maintain 500,000 colonies of resident honey bees, the number of colonies in California swells to around 1.6 million during almond pollination."

There's plenty of food for the bees during almond pollination season, as California almond acreage totals more than 800,000. Later, though, beekeepers are looking for temporary places to put their bees.

If bees were placed on prime locations, "they would require flight access to between 1 to 1.6 million acres, or approaching a maximum of 1.6 percent of California's landmass," Mussen points out.

"The demand for honey bee forage exceeds the floral quantities in areas readily available to beekeepers. To negate the need for having to feed the colonies supplemental, artificial feed, beekeepers hope to gain access to more areas that appear to contain adequate food. Besides being expensive, artificial feed does not contain all the required nutrient or the necessary microbial complex to meet the needs of honey bees."

That's why there's a concerted drive, Mussen says, for growers to provide "more bee forage along their field edges, interplanted as cover crops, or on fallow ground that they control."

Residents can do their part, too, by providing bee friendly plants.

And that's not just food for thought. It's food for the bees.

Potted passionflower vine. (Photo by Kathy Keatley Garvey)

That would be Agraulis vanillae.

Visitors to the open house saw Gulf Frit eggs, caterpillars, chrysalids and adults.

UC Davis professor Christina Cogdell, who teaches art design and history, loaned some of her Gulf Frit population, as did Bohart volunteer Greg Kareofelas and yours truly. Fortunately, museum officials collected them on a sunny Friday because the Gulf Frits would not have been flying on rainy Saturday.

The Red Barn Nursery, Davis, loaned a potted passionflower vine, which the entomologists  decorated with caterpillars. Tabatha Yang, public education coordinator and outreach coordinator, affixed a sign that read "How many caterpillars can you find?"

As one caterpillar crawled up the sign, Bohart Museum director Lynn Kimsey held up one finger, designating "One!"

As if on a cue, a caterpillar began pupating.

Butterfly expert Art Shapiro, UC Davis professor of evolution and ecology, stopped by. He had initially planned to go on a butterfly monitoring field trip, but rain dashed his plans.

All in all, it was a Gulf Frit kind of day, despite the downpour.

Seven more weekend open houses are planned throughout the 2013-2014 academic year. The next one, "Beauty and the Beetles," is set from 1 to 4 p.m., Saturday, Nov. 23 in Room 1124 of the Academic Surge building on Crocker Lane, UC Davis campus. The events are free and open to the public. All ages are welcome.

The museum houses nearly eight million insect specimens, plus a "live petting zoo" and a gift shop. Noted entomologist Richard M. Bohart founded the museum in 1946.

Check out that moustache!

Once you see the powerfully built robber fly of the Asilidae family, with its huge eyes, short proboscis and bristly "moustache," you won't forget it. It's an aggressive predator known for its speed, its strength, and its power.

The robber fly lies in wait and ambushes flying insects, including honey bees, syrphid flies,  grasshoppers, dragonflies, damsel flies and others--many larger than it is. Scientists say the robber fly stabs its prey with its short, powerful proboscis, injects a paralyzing toxin that liquifies the insides, and then sucks out the content.

Sort of like aficionados of Slurpees at the local Seven-Eleven.

Robber flies are the kinds of things you might expect in a science fiction movies--except this isn't science fiction. They've earned their nicknames of "bee killers" and "assassin flies."

These insects, found throughout much of the world (there are some 7000 species in the robber family Asilidae), can be as long as two inches and as short as 0.2 inches. 

If you look on BugGuide.Net, you can see robber flies attacking other insects, including syrphids or flower flies. 

But check out that bristly moustache! Actually it's called a mystax, derived from the Greek mystakos, which mean "moustache" or "upper lip." Some entomologists think the mystax provides some head and face protection for the robber fly when honey bees and other would-be prey fight back.

University of Minnesota honey bee researcher Marla Spivak, in her TED talk on honey bee health, referred to bees as "flower feeders."

That they are. Flower feeders.

As are other pollinators from butterflies to beetles to bats. 

But it's a special treat to see butterflies, honey bees and carpenter bees sharing blossoms of the same plant, the passionflower vine (Passiflora).

Several years ago a UC Davis professor planted a fenceline of passionflower vines at her residence off east Covell Boulevard, Davis. This year she is reaping her reward: Gulf Fritillaries (Agraulis vanillae),  honey bees and Valley carpenter bees are all over it. Why Gulf Frits? The passionflower vine is their host plant. You can see the entire life cycle from egg to caterpillar to chrysalis to adult in her yard.

The Valley carpenter bees (Xylocopa varipuncta) are frequent foragers, too. The females frighten many people because of their size and loud buzz. They're a solid black, in sharp contrast to the males, which are golden with green eyes.

We didn't see one predator Thursday in her Davis yard.

In our yard, we have scores of predators on our passionflower vines: scrub jays, European paper wasps, jumping spiders, ladybugs, assassin bugs and an occasional praying mantis.  Although the jays pick off the caterpillars from our passionflower vines, they don't seem to go for the adults. 

Butterfly expert Art Shapiro, distinguished professor of evolution and ecology at UC Davis, points to research published in a 2007 edition of the Journal of Chemical Ecology that indicates that the Gulf Fritillary adults are poisonous to birds. A team of scientists from Maryland, Virginia and Georgia wrote in the abstract of their article, “Novel Chemistry of Abdominal Defensive Glands of Nymphalid Butterfly (Agraulis vanillae):  “Abdominal defensive glands of both sexes of the Gulf Fritillary butterfly, emit a pronounced odor when disturbed…we suggest that the constituents in the glands may play a defensive role against potential avian predators.”

The article relates that Linnaeus (1758) first described the tropical butterfly and noted that its brilliant coloration of the reddish-orange butterfly makes it conspicuous.