Monday, January 2, 2017

Native Bee coloring page

Most bees are not yellow and black like we see in the cartoons. Instead, bees come in a rainbow of colors, from red, yellow and orange, to blue, green and purple.

We decided to make a coloring page to celebrate native pollinators, free for you to download. While most mason bees come in shades of blue, green and purple, we would love to see how you decide to decorate this bee.

To download a .pdf version of this, click the page tab above that says "Bee Coloring Page"

Please share your creations with us on our facebook page (, on our instagram (@the_bees_in_your_backyard), or on Twitter (@BeesBackyard).

Tuesday, December 8, 2015

Where have all the bees gone? PART 1

When Joe and I first started studying bees, the most common question we were asked by curious folks was, "Do you get stung a lot?", followed by them relating to us the story of that one time they got stung.  Bees were clearly creatures to be regarded with wariness and respect.

Now, when we tell folks we are studying bees, the most common question is: "So what's happening to all the bees?"  Despite the unforgettable moment when they were stung, most people don't appear to hold a grudge.  They are genuinely concerned about the health and well-being of bees.

Clearly no blog about bees would be adequate without some mention of bee declines, though to be honest, I am loathe to write about it.  Why?  Because it is such a hard question to answer.  Understanding bee declines is complicated.  As Winnie the Pooh was fond of saying:  "You never can tell with bees..."

First, it depends on the bee species.  Some broad brush-stroke reporting on the part of the media has convinced most of the country that all bees are suffering from colony collapse disorder, a condition that affects only one species:  the domesticated honey bee (Apis mellifera).

Setting honey bees aside for this post (we will come back to them later), in the U.S. alone there are around 4,000 species.  Each has a unique life history--they forage at different times of the year, they nest in different kinds of materials, they experience varying levels of sociality, and they specialize on different plants.  To lump all bees together and label them as "experiencing declines" makes as much sense as saying "All women are bad drivers" or "Men never read the instructions".  Obviously, it depends on the person; equally so, it depends on the bee.

Second, by definition, a population decline means that there used to be X number of individuals, and now, some years later, there are X - Y number of individuals.  The problem with studying bee declines is that we don't know 1) X or 2) how many years "some years later" should be.  Consider this:  the number of scientists studying bees in the early 1900s could be counted on both hands and feet.  Today the number is orders of magnitude greater.  As a measure of this change, the number of papers published in 1975 that had to do with bees was around 100.  The number of papers published in 2014 related to bees was over 2000!

Incredible, isn't it?  For our purposes, the point is that there were so few bee studies prior to 1970 that is hard to know what bee populations used to look like.  Even starting in 1970, the number of those studies that focused on counting how many bee species and individuals were in an area are very few.

Thus, establishing that there is a decline is harder than you might think.  For the majority of the species in the United States, we don't just plain don't know.  However, based on our knowledge of what a bee needs to survive, we can surmise that many modifications that have been made to bee habitat over the last 50 years probably aren't beneficial to native bees.  Huge swaths of the midwest that used to be wild prairie are now giant monocultures of corn, wheat, and soy--none of which are particularly useful to bees.  Acres and acres of ground-nesting habitat have been paved over, potentially eliminating homes for many North American species.  Urban sprawl isolates once continuous areas of vegetation, often fragmenting bee populations and diminishing their health.  Insecticides sprayed on crops can have the unfortunate side-effect of killing all insects, regardless of what kind they are.  Several pathogens (some known to be, and others hypothesized to be, introduced) also infect bees.

What's more, different kinds of bees probably respond differently to environmental changes.  Big bees might be less affected by small-scale environmental changes.  Specialist bees might be more affected by changes in the local flora.  Social bees likely suffer more from pathogens than do solitary bees.  Colony collapse disorder appears to only affect honey bees.

And as if that's not enough, bee populations appear to naturally fluctuate hugely.  As an example, take a snapshot from a study of orchid bees (Euglossini) collected in the same location over 20 years in Panama:  roughly 400 individuals were collected one year, nearly 1000 the next, and just over 300 the year after.  Depending on which two years you look at, it can seem that the bees are increasing (Year One to Year Two), decreasing (Year Two to Year Three), or staying the same (Year One to Year Three).  Which reflects the reality for Euglossini?

This is why scientists often look for 'trends', usually established over the biggest possible span of years.  The trend among those orchid bees, by the way, was that a few species had declined, but the majority had remained unchanged.  Unfortunately, data sets as long-term as the one in Panama are relatively rare.

One finally complication: bees are just as variable in space as they are through time.  Many bee species can't travel very far (as in, less than a football field).  If the floral and nesting resources they need are in close proximity, they may have no need to move for generations.  A study of bees on creosote bushes in Arizona found that within just 3 miles, the bee species visiting for floral resources might change as much as 67%!

Keeping those caveats in mind, there are two questions we need to ask:  Is there evidence of a decline for native wild bees?  And, if so, to what can these declines be attributed?

In later posts I'll dress the second question.   For now, I'll break down what we know about overall trends and what we know from old datasets... i.e.  Is there actual evidence of a decline?

  • At least five species of bumble bee have experienced severe declines over the last 100 years, with the most notable declines in the last 30 to 40 years.  The Western Bumble Bee (Bombus occidentalis)  used to be the most common bumble bee species west of the Mississippi.  It is now hardly ever seen in most of its range  In the east, the American Bumble Bee (Bombus pennsylvanicus) is much reduced from all but the western-most areas of its range, and some areas in the south.  Bombus affinis and B. terricola are similarly hard to find.  Most dramatically, Bombus franklini seems to be almost entirely (if not entirely) extinct.  In contrast, many other bumble bee species do not appear to have changed in their distributions (or in abundance) at all.  Why are some kinds of bumble bees in decline?  Scientists aren't certain, but several hypotheses are being investigated:  Could it be that the species in peril are ones more susceptible to the fungus Nosema bombi?  Could it be that the lower genetic diversity seen in declining species is the cause of their decline?  Or could it be that bumble bees are a hold-over from a different, cooler, era, whose extinction is inevitable as the world warms?  The verdict is out.
  • A study in 2013 looked at all bee records for the northeast over the last 140-plus years.  The authors picked out 187 species that had been relatively commonly collected and looked for trends in population size based on how often the bee has been collected over that time span.  Three species have declined significantly and dramatically--two of those three were bumble bees.  One was Macropis patellata, a specialist on loosestrife (Lysimachia).  A little under 29% have declined a little bit.  And a little over 27% have increased in abundance.  The authors tried to find commonalities among the species that have declined; while the evidence was weak, it did suggest that bigger bees might be more likely to be in decline, as might specialists.
  • In the midwest, near Carlinville Illinois, Charles Robertson (one of this U.S.'s earliest pollination ecologists) studied 441 flowering plants.  For each plant, he meticulously recorded every flower-visitor for two years.  The result is a fantastic record of nearly all bee species in that part of the country and their floral preferences.  For two years in the 70s, two scientists resampled 24 of the plant species that Robertson had sampled.  They found 82% of the bees Robertson had found on those same plants species, as well as 22 species Robertson didn't collect.  
  • To add to this dataset, the area was again resampled in 2009 and 2010, this time focusing on 26 flowering plant species.  Of the 109 bee species Robertson had recorded on those 26 plants, the scientists found only 54.  However, many of the species that Robertson had collected might be considered 'incidentals' on those plants.  For example, one missing in 2009 that Robertson had seen 100 years before was Andrena erythrogaster, a likely specialist on willows (Salix).  As they did not collect on willows, it is possible the bee is not extinct, but is just not commonly found on other plants; i.e. Robertson's record may have represented a fairly rare bee/flower connection.  Also, roughly a dozen of the bees missing in 2009 are parasitic species; bees that do not visit flowers for pollen, but only for nectar.  Their absence, again, may not represent a loss of those species in the area, but just that they weren't on these particular flowers.  All of which is to say there has been some change in bee visitors to these particular plants in the last 100 years, but the significance of this change and what it tells us about bee declines in the midwest is hard to say.  
  • Some species have dramatically expanded their ranges.  Take the example of the squash bee, who has expanded its range from the southwest all the way to Maine in the last 5,000 to 7,000 years ago, both as North America has warmed, and as humans have planted squashes outside its 'natural' range.  Or the more than two dozen introduced species in the U.S. and Canada; Anthidium manicatum has made it from the east coast to the west in less than 50 years.  
So what can we conclude from these few studies?  Some bumble bee species are in serious trouble; though the reason why is unclear, the species most in decline are also the ones most susceptible to Nosema.  The status of other species in the U.S. is largely unknown, though there is a little evidence that specialist bees and large-bodied bees have disproportionately shifted (decreased?) their ranges.  Many species appear not to have changed their distributions, and some species are more common.  

Perhaps the conclusion we will eventually reach is that, just as "Global Warming" as a catch-phrase has proved inaccurate, so too will "Pollinator Declines".  Perhaps "Pollinator Shifts" more accurately reflects the trends we are seeing, as some species retreat to cooler refugia, and others embrace the warmth of the once-inaccessible northern reaches (the majority of the world's species thrive in the heat).  Overall diversity may not be changing in North America, but the bees making up the neighborhood, and the 'hotspots' of biodiversity, may be shifting.

Tuesday, October 20, 2015

Check it out!

Princeton did a little Q&A with us (who we are, what our favorite bees are, our thoughts on bee declines and conservation, etc.)  They've published it on their website, along with a nifty little slideshow with some of the pictures from the book.

Take a look, and let us know what you think!

Friday, September 11, 2015

The Accidental Pollinator

It seems we all know that pollinators (especially bees, who do most of the pollinating) are important, but did you know they aren't doing it on purpose?

The bright yellow pollen of a Mallow flower.
Pollination is the transfer of pollen from anthers (loosely, pollen is the male portion of a flower) to stigma (a part of the female portion of a flower).  Ideally, pollen from one flower ends up on the stigma of another flower, on a different plant of the same species.  Obviously, a flower can't uproot itself and stalk (puns intended) over to another plant to shake off a little excess pollen--pollinators are required.  Wind was the original pollinator, and many plants still rely on a light breeze to whisk away their tiny grains.  But somewhere along the lines, flowers "realized" the value of employing conscious couriers; wind can be whimsical.  If it doesn't blow (say, in the rain forest), a hopeful plant is out of luck.  If it blows the wrong way, pollen may be carried away, but to no good end. 

An insect rests on a California Poppy.
In contrast, insects seek out flowers for bite or a sip, for meeting up with the ladies, or as resting places.  Notice that not one of those reasons for visiting a flower is:  "to pollinate a flower".  Selfish creatures, insects are accidental pollinators.  As they muck about on flower heads, pollen grains adhere to their body parts (it is no accident that pollen grains are sticky).  Then, as they move from flower to flower, pollen grains are transferred.  Historically, this relationship has been referred to as a mutualism—one in which both partners benefit from the interaction.  While this is most certainly true, it is more complicated, especially when it comes to bees…

A Centris female, with full pollen loads (success!)
There are two points of view when it comes to this mutualism.  Consider the female bee:  her goal is to harvest as much pollen from a flower as possible, scraping,shaking, and squeezing it out of anthers and packing it tightly into her scopa—stiff leg hairs evolved specifically for holding pollen (they are even slightly electrostatically charged).  The more pollen she gathers, the more bee larvae she can provide for, and (therefore) the more successful she is as a parent.  To maximize her success, she sometimes limits herself to just one type of flower on foraging bouts—having to remember how to operate the various bits and pieces of, say, only cactus flowers is easier than trying to remember cactus flowers, penstemons, and also daisies.  She also moves quickly.  The faster she can gather the pollen, dump it at her nest, and get back out for more, the more babies she can provide for.  Any pollen ‘lost’ to a flower’s stigma as she moves about represents a failure, from her point of view. 

From the plant’s point of view, female bees are a bit of a conundrum.  They represent the best transporters of precious pollen grains—they are the most likely pollinators to visit consecutive flowers of the same species, and they move quickly, therefore shuffling a large number of pollen grains between flowers every day.  At the same time, they are thieves, and the majority of pollen handled by female bees is lost to the flowers.  As a result, flowers have had to evolve devious ways of manipulating bees—encouraging them to visit, but hurrying them on their way before they’ve done too much damage.

The many colors, shapes, and scents of
flowers are meant to draw in
potential pollinators.
On the one hand, flowers advertise; they lure bees in with the promise of sweet nectar, indicated by a heady scent detectable from great distances.  Like highway billboards, they promise all-you-can-eat buffets, unfurling petals in eye-popping shades of blue, and pink, and yellow, and orange, and even ultra-violet.  On the other hand they play hardball. Visitors to flowers with narrow corolla tubes are limited to those with slender waists.  Pollen grains are often coated with a toxic layer; a bee might enjoy a sip of nectar from a flower, but find the pollen unpalatable, and shed it at its earliest convenience.  Fruit trees frequently have ‘blank’ flowers; among the cornucopia of nectar-producing flowers on one tree are empty ones.  Disappointed bees often leave a tree and move on to another when they encounter two or more blank flowers in a row (thus guaranteeing at least some cross-pollination).  Some kinds of pollen grains also often have points and spines on them that prevent them from being packed too tightly onto bee legs (especially honey bee and bumble bee legs), making it easier for them to fall off when the bee lands on a new flower.

A Xylocopa steals nectar from a flower whose corolla is too
narrow for its burly body.
Not to be outdone, bees counter with their own maneuvers.  Narrow corolla tubes are bypassed by nipping a hole in the base of the flower, sipping out nectar without ever touching the anthers or the stigma.  Specialist bees have evolved hardy stomachs, capable of ingesting otherwise poisonous pollens.  Many bees are capable of smelling flowers before they land, assessing the quantity and quality of nectar and pollen before they waste their time,  Finally,some bees have extremely widely spaced pollen-collecting hairs (scopa), capable of holding even giant spiky pollen grains. 

Are bees important pollinators?  No doubt.  Perhaps THE most important, from the point of view of the majority of the world's flowers.  Nonetheless, their services come at a hefty price to the flower, seen most clearly in the amazing variety of shapes, colors, and scents on display in any flower patch.

Friday, August 14, 2015

What is a bee, exactly?

To best understand bees, one needs to know exactly what a bee is.  The answer is, at the outset, simple, but there are complications.

First off, bees are insects that belong to the order Hymenoptera, which includes ants, sawflies, and wasps.  Studies of bee DNA have shown that they are in fact close cousins to modern-day wasps, with whom they share a common ancestor (i.e. a many-greats grandmother).  In other words, bees are a kind of wasp.  What distinguishes bees from wasps?  Most of the time it is behavior:  a bee collects pollen and nectar to feed to its young.  Wasps capture insects for their young to devour.  However, there are some wasps (Pseudomasaris) that have evolved to collect pollen for their offspring, and there is a group of bees (some Trigona species) that has evolved to collect rotting meat for their offspring. Behavior alone, then, doesn't separate all bees from all wasps.

Better put, then, bees are those wasps who share a common pollen-collecting ancestor.  The descendants of this ancestor are said to all belong to the same 'clade*':  Anthophila (which means flower-loving).  Their pollen-collecting behavior has led bees down and evolutionary pathway th
at has resulted in furry bodies and pollen-collecting appendages, while the wasp's predatory lifestyle has led to long spiny legs and no need for extra hair.

A few groups of bees have given up collecting pollen and instead let other bees do the hard work for them.  These 'cuckoo bees' lay eggs in the nest of another bee who does collect pollen.  The cuckoo bee larvae destroy the 'host bee' larvae and then eat their pollen.  Cuckoo bees tend to look more wasp-like as they have shed the hairy vestiture typical of pollen-collecting bees.  Nonetheless, DNA analysis tell us that they share the same pollen-collecting wasp ancestor as other bees (they are in the same clade).

There are probably close to 30,000 species of bees around the world.  20,000 of them have been acknowledged by scientists, but many areas of the world have not been thoroughly sampled, and likely harbor species currently unknown to us.  Contrary to popular belief, most bees don't live in hives.  There is no queen.  And they don't make honey.  In fact, of those 20,000 known bees, only 7 are honey bee (Apis) species.

The majority of bee nests are in the ground, dug by bees who also collect pollen and nectar, and also lay eggs (functioning therefore as both queen and worker).  The honey bee lifestyle we know so well is the exception rather than the rule for most bees.,, but we will delve into that later.

*  Think of a clade as an exclusive branch of a family tree.  All descendants of Grandma and Grandpa Smith, for example; Grandma's sister's kids would not be part of the Smith Clade.