The conversation usually starts like this:
"I saw this huge, huge bumble bee with yellow on its back. It was buzzing like crazy."
Often it's not a bumble bee, but the Valley carpenter bee, Xylocopa varipuncta, that's been foraging on the blooms of the passionflower vine (Passiflora).
The yellow "markings?" Tiny yellow grains of pollen.
Valley carpenter bees are passionate about the passionflower vine, a robust climbing vine that's the host plant of the Gulf Fritillary butterfly (Agraulis vanillae).
The Valley carpenter bees are large (about the size of a queen bumble bee). The females are solid black, while the males are golden/buff-colored with green eyes. If you're lucky, you'll see both on your passionflower vine.
Planting Passiflora will usually result in a diversity of visiting species, from butterflies to honey bees to carpenter bees. You'll see Gulf Frits laying their eggs on the leaves and tendrils.
Yes, the vine will cover your fence, but not for long. The Gulf Frit caterpillars will skeletonize the plant. (And that's why we plant ours--for the Gulf Frits.)
Well, also for the other insects, too!
We remember seeing a varroa mite attached to a foraging honey bee one warm summer day in our pollinator garden. The mite was feeding off the bee and the bee was feeding on the nectar of a lavender blossom.
Didn't seem fair.
We've never seen a varroa mite on bumble bees or carpenter bees, but Davis photographer Allan Jones has--and he's photographed them. (See below)
When varroa mites tumble off a honey bee and into a blossom, they can hitch a ride on other insects, such as bumble bees and carpenter bees.
"Varroa have been recorded hitching rides on bumble bees and yellowjackets," observed native pollinator specialist Robbin Thorp, distinguished emeritus professor of entomology at UC Davis. "Varroa have been reported as feeding on larvae of these and other critters--but not successfully reproducing on them. Also bumble bees and yellowjackets typically overwinter as hibernating queens not as perennial colonies like honey bees. Thus they are not suitable hosts for Varroa."
Extension apiculturist emeritus Eric Mussen says that bees other than honey bees aren't reproductive hosts for the varroa mite.
"As far as I know, Varroa destructor may be able to find soft areas of the exoskeleton of insects other than honey bees and feed on them," he says. "I have no idea whether or not the substitute hemolymph would sustain the mites for very long. The mites have practically no digestive capabilities. They simply utilize the previously-synthesized bee blood, to which they seem to be perfectly adapted."
"Since the mites reproduce on honey bee pupae, there are a number of considerations about potential other reproductive hosts," Mussen said, citing:
- Are the nutrients of the substitute host close enough to those of honey bees to support immature mite development?
- Can immature mites that develop properly at honey bee cell environmental conditions (temperature and relative humidity) find a similar environment in the nests of other insects?
- Do other insects tolerate the presence of mites on their bodies or in their brood nests?
Like honey bees, bumble bees do segregate their pupae in single cells, Mussen says, but he was unable to find any studies devoted to whether bumble bee pupal conditions support Varroa destructor reproduction.
Sounds like a good research project!
We all take shortcuts.
We look for the shortest line at the supermarket, we use keyboard shortcuts, and we text ”how r u?”
So, why shouldn't honey bees use shortcuts? They do.
If you've ever watched a carpenter bee drill a hole in the corolla of a tubed flower to get at the nectar—this is "nectar robbing" or bypassing pollination—you may have seen a honey bee come along and sip nectar from the hole. Why work hard to get at the nectar when it's right there for the taking?
This is the insect version of a convenience market!
Take the foxgloves (family Plantaginaceae, genus Digitalis). Sometimes you'll see a honey bee trailing or shadowing a carpenter bee that moves from corolla to corolla.
Short cut to the nectar!
Foxgloves are called "the lurking place of the fairies."
That could be.
Foxgloves are also known by their genus name, Digitalis--meaning fingerlike. The genus is native to western and southwestern Europe, western and central Asia, Australasia and northwestern Africa.
Question: Have you ever pulled off the flowers and gloved them on your fingers? Probably. Not good for the plant, but what fun!
The common foxglove, Digitalis purpurea thrives in a shady spot in our yard. The honey bees and carpenter bees love it, as does a single earwig, which apparently considers it its "hidey hole."
How did it get its name? Legend has it that a botanist Fuchs first named it and the name corrupted or morphed into foxglove, according to Wikipedia. "It happens, moreover, the name foxglove is a very ancient one and exists in a list of plants as old as the time of Edward III."
Reports Wikpedia: "The 'folks of our ancestors were the fairies and nothing is more likely than that the pretty coloured bells of the plant would be designated 'folksgloves,' afterwards, 'foxglove.' In Wales it is declared to be a favourite lurking-place of the fairies, who are said to occasion a snapping sound when children, holding one end of the digitalis bell, suddenly strike the other on the hand to hear the clap of fairy thunder, with which the indignant fairy makes her escape from her injured retreat. In south of Scotland it is called "bloody fingers" more northward, "deadman's bells" whilst in Wales it is known as "fairy-folks-fingers" or "lambs-tongue-leaves."
No matter the origin, the exotic-looking freckled purple foxgloves will long be a favorite--not just by us, but by all the pollinators.
And a few earwigs.
We all take short cuts--short cuts around the campus, to the beach, to a favorite restaurant...
Honey bees take short cuts, too.
We've often watched assorted bumble bees and carpenter bees drill a hole in a long-tubed flower to rob the nectar.
And we've watched honey bees benefitting from this behavior.
Today we observed a carpenter bee, Xylocopa tabaniformis orpifex, engaging in nectar robbing in salvia at the UC Davis Arboretum. Nectar robbing occurs when a bee or other animal circumvents the usual plant-pollinator relationship and "cheats" by entering a flower from the outside to steal nectar, thus avoiding pollination or contact with the anthers.
There's excellent information on bumble bees, their habitat needs, their behavior, and identifying characteristics in a free, downloadable PDF from the Xerces Society for Invertebrate Conservation: "Conserving Bumble Bees: Guidelines for Creating and Managing Habitat for America's Declining Pollinators."
The PDF mentions that "short-tongued bumble bees will engage in 'nectar robbing' from flowers with a long corolla tube by biting holes at the base of the corolla and drinking the nectar from the outside of the flower." The bee grabs the reward but doesn't contribute to "the plant's pollination needs."