Pollination talk, Part II Bees, Master Pollinators and Pollen Pigs

Carpenter Bee with loaded scopa

Most female bees, solitary as well as social species, collect pollen for their offspring. Great fliers, fury, intend on their task, they zip from flower to flower as fast as possible while filling their pollen collection areas on legs or bellies. 

Leaf-cutter bee, loaded with pollen on her underside

They usually concentrate on just one species of flowers at a time - it makes them most efficient. They gather as much and as fast as they can - to provide for as much offspring as possible. Pollen that actually reaches the next flowers stigma is wasted - from the bee's point of view. 

From the plant's point of view, bees may be the fastest and most reliable transporters of pollen between plants of the same species, but they also carry off most of the pollen for their own purposes.
Again, adaptive evolution on the plant's side: 
-we already talked about narrowed access to many flowers that at least excludes the biggest bullies. 
-Some flowers offer nectar, but their pollen is toxic or unpalatable, so the bees quickly get rid of it. 
-Have you seen cherry trees covered in blossoms, buzzing with bees? There are many 'blank' flowers without pollen or nectar among the ones loaded with both. So busy bees will happen upon those, and after a couple of encounters will be encouraged to move on to another tree - which also keeps cross pollination going.  
-Although pollen is usually sticky or statically charged to cling to an insects 'fur' many pollen granules have spikes that prevent the bees from packing it too tightly into their scopae, so hopefully some pollen will fall off to actually pollinate a target stigma.

Tiny fairy bee Perdita sp and giant Carpenter bee Xylocopa sp (photo Joe Wilson)

Of course, the dance of co-adaptation made bees evolve into  tiny fairy bees (Perdita) and gigantic Carpenter bees, and 4000 north American bee species in between. So bees slither or bite through the narrowest throats, became scent-hounds that can tell 'blanks' from a distance, adjust the density of transport hairs to carry the spikier grains and some even specialize in and digest the undigestable pollen. (after: The Accidental Pollinator by Joseph Wilson)

Poster by Joseph Wilson (available on his website)

Honey Bees, Apis mellifera, the imported competition

As an agricultural tool, Honey bees outrank most other pollinating insects. There are quite a few endemic bee species that have the right behavior and physical attributes to be as efficient, but, being highly social, honey bees are available in masses, active throughout the vegetation period, and, most importantly, transportable,  They are also not specialized, they harvest honey and pollen as opportunists. Honey bees can service most crop plants that are grown in huge mono-culture. We don't try to mass produce orchids in an agricultural setting.  So honey Bees are still the most useful species (group) from the human perspective. Their role in the natural ecosystem, however, might be much less positive and can probably be even detrimental where they are brought in by humans and become invasive, as here in the Southwest US. Honey bees can bully endemic bees and out-compete them. They may harvest pollen so thoroughly that not much is left for endemic species once a big hive of HBs has found a pollen source. Remember that this is mostly desert and flowing plants can be few. 
The fact that hives can be moved in and out of an area also allows for the intensive use of pesticides when the bee keepers have moved on. This heavy use of pesticides indiscriminately kills off local pests and pollinators alike.

New study shows strawberry plants 🍓 pollinated by wild bees result in bigger fruits than those pollinated by honey bees. Andrena (mining bees) are some of the most frequent visitors.

As for the question if HBs actively compete with native bees - to the detriment of the latter - see this video of HBs stealing collected pollen from the 'baskets' of a Sonoran Bumble Bee https://www.facebook.com/philipp.wickey/videos/10157772746482921/

A change in public perception: Killer Bees or threatened pollinators

Wikipedia says it quite correctly: "A new honey bee colony is formed when the queen bee leaves the colony with a large group of worker bees, a process called swarming. In the prime swarm, about 60% of the worker bees leave the original hive location with the old queen. This swarm can contain thousands to tens of thousands of bees. Swarming is mainly a spring phenomenon, usually within a two- or three-week period depending on the locale, but occasional swarms can happen throughout the producing season."

So 'Italian' Honey Bees are supposed to do this in spring, and not too often. But our Arizonan Africanized colonies seem to  break up more frequently, and you see small swarms at all times of the year. Big colonies are important for effective communal thermoregulation in winter. The Italian bees, supported by their keepers, usually survive very low temperatures by shivering and huddling. The African Bees are not that cold tolerant - so the cold winters in Germany and the northern US  kill them off, but in Arizona they often survive, even in feral hives. By now all feral hives in Arizona are assumed to be Africanized.
Accordingly, here in Picture Rocks  our feral bee populations were greatly reduced after the very cold winter of 2012/13. In spring of 2013, we saw very few honey bees at hummingbird feeders and bird baths (we don't have any closeby bee keepers). But all through  2014 I again saw swarms searching for homes, Saguaro holes turned into bee hives, and bees visiting  hummingbird feeders. The (probably Africanized)  honey bee population of Picture Rocks Arizona is bouncing back just fine.
Local endemic bees beware, they are going to be strong competition again.

Feral honey bees drinking at a bird bath. The whole rim was covered like this. Bees are not aggressive in this situation, or when they nectar on flowers

 In the past, swarming bees alarmed the public. Africanized Bees were seen as a deadly menace. With some justification. If those bees try to defend their hive, be careful. By hive I mean an established colony that has honeycombs and, most importantly, eggs and larvae to defend. They may attack if you get close and or do disturbing things ... like hammering or mowing lawns.

This saguaro hole on our property house bees for years. That high up they felt safe and never caused any trouble

 If you run they will follow, but not very far. A few stings are what you will suffer before you have outrun them. But deaths have occurred when people stood their ground and swatted at them or were unable to get away. The sad case of a rock climber who died hanging in his harness speaks for itself.

Resting swarm. Not dangerous at all

 But when swarms are encountered out in the open before they find a new home and become territorial, there is no threat to the observer. The queen lands on a branch, all others follow, held together by her pleasant smell. A big obvious cluster of bees hangs in a tree. Scouts will be sent out, looking for a nice hole that might be the new homestead. You can only hope that they do not chose the rafters of your house.  But the big, scary clump of bees in the tree is harmless. The stomachs of these travelers are full of provisions for the journey, and they are lazy and docile, Africanized or not. No need to run from a swarm like that. The worst that can happen: the queen lands in your beard. Then you may end up covered in bees. But not stung.

Over the last years, the mass media has been talking about the demise of pollinators and, in that context, hyped up the buzz-word 'beehive collapse'. To the ecologist these are two different phenomena. Endemic pollinator populations are definitely suffering all over the world. Important roles are played by drought and climate change, intensified agriculture, monocultures, pesticides, weed control along roads and between fields that eliminates the bees' food and kill them directly.  Equally detrimental: development, and even overly groomed gardens where mulch and plastic foil cover breeding grounds, and dead wood and plant material needed for breeding are cleaned away. It makes reproduction impossible and no pretty 'bee hotels' can make up for the loss of natural breeding places.

As for the honey bee hive collapse, it is a number of factors acting together. Mites and neonicotines certainly play their roles. So does insufficient winter food, after too much honey is removed and replaced with poor substitutes. But industrialized beekeeping and agriculture pose a problem that is more difficult to pin down. Millions of bees are shipped all over the continent, shuttling constantly between almond orchards in California, rape fields (Canola) in the north, and wherever else big monocultures demand pollinators in unnatural numbers. Thus infectious germs are distributed in a modern, borderless fashion.

This container truck full of bee hives overturned. But even save travel means stress for bees, who rely on a sophisticated orientation system that is almost certainly confused whenever they are shipped long distances

 Stress weakens immune systems, not just in humans. Researchers in Norway, for example, have clearly demonstrated the negative impact of transport stress on the survival rates of smalt (young salmon) that were shipped from breeding facilities to aquaculture farms. Those smalts

As press releases about the sad fate of pollinators are reaching the public,  the trend here in AZ has slowly changed from concern about dangerous killer bees to concerns about the well being of our Honey Bees. Again, as a biologist I'd say that the imported honey bees and the invasive feral bees (same thing but escaped from the care of the bee keepers) are by far not as important as our less visible endemic bees. But any kind of public concern about the well-being of mere insects should probably be applauded.

Lately I have seen a number of Facebook entries that described honey bees that were inexplicably dying. The presumed culprits ranged from poisonous nectar of blooming Tamarisk (invasive and bad in many ways, but not killing honey bees who actually originated in the same area as the tamarisk), to  neighbors spraying insecticides to Carpenter Bees attacking the hive, killing the inhabitants and stealing the honey..

Photo by Les Stewart, with permission

The last assumption reminded me of a famous Germa children story (Die Biene Maja by Waldemar Bonsels) describing a raid of  Hornets  (Vespa crabro) on a bee hive - they catch the honey bees, masticate them into food for young hornets, and they steal the honey. This terrible story kept me awake at night, but it is credible. Wasps and hornets are predators, and stored honey and pollen does get stolen, not only by marauding wasps but by other bees, beetles, birds, bears and men.

But Carpenter Bees killing large numbers of honey bees during a raid on a hive?  The above picture came with the story: the assumed culprit, a very large bee, impaled on a huge pin. The photographer had observed  big bees approaching the hive, a tussle, and later dead bees on the ground. He collected the evidence and came to his conclusion, probably because  Eastern Carpenter Bees  look not unlike big honey bees.

To me, the photo tells a different story: On the pin is a dead male honey bee, a drone.
While most of the inhabitants of a bee hive are females and sisters, all daughters of the mother queen, at certain times a number of males hatch from the brood cells. They have only one purpose: they will mate with new queen bees that are also emerging at that time. Young queens and drones go one bridal flights to mate, and the new queens will store sperm from this one mating to produce hundreds of offspring. So the role of the males is over after that one romantic adventure. Since they have nothing else to contribute to the well-being of the hive, the workers will not feed them. They will actually not let them back into the hive. Scuffles may happen when the gate keeper bees refuse entrance to the returning drones. Observers may think an attack is going on. No. It's just the expulsion of the useless drones. But dead bees can be found at that time. At the hive entrance, but also under a tamarisk tree close by. Look into their eyes. Those are the expired drones.

Here is a close-up of the swarm above. You can see the huge drone on the right. His eyes are big and touch on top of his head: he will be able to not just smell his beloved but see her in his aerial pursuit. Check out the smaller worker bee on the left with widely spaced eyes.

  

Desert Bees

We have a collection of early spring bloomers in our backyard, a mix of imported and native species. Right now, there are several penstemon species, aloes, creosote and brittle bush in full bloom.

Parry's Penstemon is a native species. It can be found in many sandy washes of the Tucson Mountains and beyond. In our garden it is blooming in direct vicinity of several showy Aloe species.

The imported Aloes attract the equally imported Honey Bees, and birds who are not very fussy when it comes to sweet juices.

 Hummingbirds, Gila Woodpeckers and Orioles are frequent visitors. But the native Parry's Penstemon is visited by local specialists.

Habropoda  and Anthophora Bees hover from flower to flower, land, and are gone again. Every flower seems to yield  only a very small amount of nectar. This makes life difficult for macro-photographers, but even more so for the bees.

This becomes obvious when the sun disappears shortly behind a cloud resulting in an immediate drop in temperature. Some bees keep going and going. But others soon drop out of the race for nectar. They clamp their mandibles on a leaf or a stem, tuck their legs and rest motionlessly. I can see that they do not carry any loads of pollen, and when one finally starts moving again I see a flash of white from the face: the bees that take brakes seem to be all males. They may stop flying when the temperature drops and they would have to spend extra energy on heat production to keep their flight muscles operative. For males this expenditure may not be worth it. The resting individuals also looked old and ragged. Maybe they have done their duty.

The pollen loaded females who are provisioning their nests seem to have reasons to invest more energy and keep flying, at least at our only slightly sub-optimal temperatures. 
 Habropoda  and Anthophora are Anthophorine Bees with very long togues (0.4 to 0.8 inches) that enable them to pollinate deep flowers (O’Toole & Raw 1999). Adapted to both temperate and tropical climates Anthophorines are wide-spread, but in the US most abundant in the West and Southwest. They are called mining bees because they are solitary ground nesters whose females dig tunnels in the soil to accommodate a series of brood cells. The cells are lined with an oily substance for protection against moisture and fungal infections.

While watching the bees for hours on several days I saw very few honey bees visit the Penstemon, but quickly return to the aloes. The native Habropoda  and Anthophora Bees completely ignored the aloes and concentrated on just one species of penstemon and the surrounding creosote bushes. Every evening, when it's too cool for most bees, a big female Carpenter Bee also harvests pollen from the creosotes. I will have to use a flash to get her photo.

See also:
The Great Sunflower Project, Anthophora – mining bees (family Apidae)
by Lisa Schonberg and Mace Vaughan (Xerces Society) and Gretchen LeBuhn (SFSU)