Rain and Pollinators

Where do pollinators go when it rains? You certainly don't see many of them around when it is pouring. They may be sturdy little fellows but they have some limitations. Wind or rain (or even cloudiness) can be too much for most of them. Cold weather also makes them think twice before going outside.

Gathering of male Andrena bees early in the morning

There are many different kinds of pollinators: bees, flies, butterflies, moths, and a few other insects; not to mention a few non insect ones such as many kinds of birds, bats and even a few other mammals. Let us look at one group in particular, bees. Bees probably do about 90% of all pollination so they deserve our attention. Bad weather is too much for most of them, but some fare better than others. A few bumblebees tolerate the cold of the Arctic Circle. Some bees fly at dawn or dusk or in the very early spring, although the majority prefers the daytime, sunny weather and warm temperatures. Wind is harder to overcome than chilly weather. There are physical limitations to flight, so when the wind reaches certain speed all flying insects find themselves grounded. That is why a steady breeze brings welcome relief from mosquitoes and gnats.

Rain is a serious problem to insects; a mere drop of rain is the equivalent of a big bucket to us; it would knock them down harshly. The weight of the moisture clinging to their bodies proportional to their own body weight would also be a major problem.

Insects are sensible enough to lay low when conditions are severe. Females return to their nests and stay there. Males, on the other hand, do not have nests to return to; they are not homemakers and know nothing about nests so they resort to a different kind of shelter. The males of many species seek each other company. They may stay in groups on flowers or leaves, or hanging from twigs. They clamp their strong jaws onto a twig and go to sleep this way. There are times in the early morning in which you can find one of these roosts. The insects may be dew covered and very sluggish and will need some sunshine before they can start moving around. Others cluster inside large flowers such as squash. These places offer some protection from the weather.

Carpenter bees spending the night clinging to a Passionaria flower

Probably these roosting places are not as secure as the nests where the females stay and this may very well be one of the reasons why male lives are shorter than female's. Males only mission in life is to mate; after that they are dispensable. Females, on the other hand, need to live a little longer in order to build nests, gather food, lay eggs and seal the entrance to their nests.

Sometimes, after a particularly rainy spring, trees produce very little fruit and one wonders about the connection between the abundant rain and poor crop. What happens is that the pollinators didn’t have enough opportunity to visit flowers because of the weather.

It is interesting that many native bees can face these hardships better than honey bees and turn out to be better pollinators under certain circumstances. Honey bees are very quick to return to their hives when weather conditions are poor. They also work shorter hours, starting later in the morning and quitting earlier in the afternoon. Some bee specialists say that native bees and bumblebees are not unionized and find themselves forced to work longer hours and under poorer conditions.

Roosting male bees

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Magnolias and Beetle Pollination

Magnolias were among the earliest flowering plants, which evolved many million years ago, long before there were any bees. Butterflies and moths were also absent in those days. The only pollinators available were probably beetles and flies, the so-called “dumb pollinators”. This term refers to the fact that the late-comers to the world of pollination, particularly bees, can perform remarkable feats of memory and skillful manipulation of flowers.

When bees entered the scene, perhaps twenty or thirty million years later (give or take a handful of millions), they took to the pollinating job with gusto. They became real pros which adapted to the ever growing variety of flowers and developed skills par with the complexity of these newly evolved plants. The same can be said of many butterflies and moths and also some wasps. That is how they earned the name of "smart pollinators".

Neither magnolias nor beetles are very specialized to pollination by insects. The flowers, though lovely have a very simple structure; for instance, there is no distinction between petals and sepals as in most other flowers. In turn their pollinators, beetles, are very clumsy at their task; sometimes they get carried away and eat parts of the flowers along with the pollen they find there. Their mouth parts are made for chewing, rather than for gathering nectar and pollen, so they can’t be blamed for their sloppiness. The flowers, in turn, are adapted to this rough treatment; that is why magnolia petals tend to be rather leathery; and, most importantly, the seeds are well protected.


You develop a new respect for the pollinating responsibility of beetles when you take a look at the many families of these insects that visit magnolia flowers: sap-feeding beetles, tumbling flower beetles, leaf beetles and weevils, among others (or if you prefer their technical names: Nitidulidae, Mordellidae, Chrysomelidae and Curculionidae).



Bees, bumblebees, flower flies, a few types of stink bugs, leafhoppers and several other types of insects are also found visiting magnolia flowers attracted by their nutritious pollen and nectar.

But most of them arrive at the flowers too late, after the blooms are past their prime and are not receptive for pollination. So it is the beetles that carry the lion's share of the responsibility for perpetuating these plants.

Beginners Guide to Pollinators and Other Flower Visitors

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© Beatriz Moisset. 2012

Nectar: Drink with a Zing?

We saw that floral nectars aren’t just empty calories (Nectar: Breakfast of Champions); they supply pollinators with valuable nourishment. The singular properties of nectar don’t end up there. When chemists continued analyzing the nectar of diverse flowers they found a few surprises.

In some instances caffeine or nicotine are added to the menu. Who would have thought! Then again, if bees love spilled Coca-Cola, it is perhaps for more than the sweetness. Do the clients of floral restaurants seek these stimulants? Do flowers find it important to indulge such demands? One thing is clear: some special ingredients in nectar must be important, both for the pollinator and the flower.

There are cases in which the sugar in nectar ferments into alcohol to the point that it may intoxicate thirsty flower visitors. Bumble bees visiting such flowers behave like drunken sailors, bumping clumsily into flower parts, shaking loose the pollen from the anthers and thus getting an extra dose of pollen dusting. Moreover, they neglect their fastidious grooming and remain rather dusty all over for some time. Perhaps this is beneficial to the flower which may end up getting more pollination under these circumstances. Nobody knows for sure but it is an interesting theory. I wonder whether the little gourmets develop a taste for certain vintages and visit more frequently the restaurants that deliver the desired beverage.

The flowers of a palm tree in Malaysia produce alcohol that can reach a concentration of 3.8%, comparable to some beers. And the tree smells like it! There is a little tree shrew, a fairly unusual pollinator, which visits these flowers assiduously. Up and down the trunk it runs visiting thousands of flowers. It is capable of drinking the equivalent of nine glasses of wine, day after day during the blooming season. Those who have studied this behavior claim that the animals show no sign of loss of coordination or similar consequences of heavy drinking.

Pollinators do a lot of traveling in their quest for nectar and pollen. They carry more than what is intended from flower to flower. Like tiny typhoid-Maries they are likely to pick up and spread pathogens along with their legitimate cargo of pollen. Nectar is the perfect culture broth for many bacteria and fungi. Flowers can become quite sick so they need to protect their precious reproductive organs against infections. It should come as no surprise that they can produce an assortment of antiseptics. There are substances in nectar that produce peroxide, the same disinfectant your mother used to apply to your scraped knees.

Perhaps the most mysterious thing is that some nectars carry bitter tasting substances and even toxins. What would be the purpose of that? Some of the bad tasting ones deter only some flower visitors, while they don’t bother others. Perhaps the plant is being selective, inviting only the most efficient pollinators and keeping others away. It is also possible that some pollinators can only tolerate a small amount of the bitter nectar, thus, abandoning the flower sooner and performing more pollination with less consumption of nectar. Let us remember that nectar production is an expensive investment for the plant.

Most plants produce toxins to protect leaves, stems, etc. against the hordes of herbivores. In other words, plants synthesize organic pesticides. Ordinarily they filter out these toxins from the nectar. But some accomplish this only partially. It seems like an unfortunate side effect, an instance of unintended contamination. Perhaps we are not the first ones to run into such a problem, plants made that blunder millions of years ago.

Nectar chemistry
Nectar, the first soft drink
Tiny treeshrews chug alcoholic nectar without getting drunk
Nectar, breakfast of champions

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© Beatriz Moisset. 2012

Nectar: Breakfast of Champions

I used to believe that flower nectar was sugary water and not much else. That simple drink should be adequate for many of the insects that visit flowers. Sugar provides the fuel to power their flight, thus taking care of a fundamental need. Many insects have a very short adult life. They have already accumulated, during their larval life, most of the nourishment that they need as adults. In fact there are even some insects, such as the Luna moth, that do not feed at all as adults. Moreover, nectar drinkers often have other foods in their menu. For instance, bees collect pollen, as well as nectar, from flowers; wasps hunt insects. So it wouldn’t be surprising if nectar provided nothing more than sugar as a reward to pollinators.

I was wrong, but I wasn’t alone in my ignorance. Only recently, scientists have been able to study the chemistry of nectar, given the tiny amounts available for study. What they have learned in recent years surprised everybody. Nectar is a true cocktail including an assortment of substances, from nutritious to intoxicating, not to mention scented, colored or with preservatives. Flowers are known for the complexity and diversity of their shapes and colors. Now we know that their nectar can be just as rich in complexity and variety. Nectar drinkers seem to be connoisseurs of the restaurants they visit and flowers must have good reasons for developing such a complex menu to satisfy the demands of their clientele.

First of all the concentrations of sugars vary depending on a number of factors. Perhaps, the most important one is the most frequent visitors of a particular species. Butterflies and moths and some bees have very long tongues which they use like drinking straws. They visit flowers that provide a rather watery drink not likely to clog these very thin pipes. On the other hand, other insects, with shorter tongues, merely lap or slurp fluids and can take advantage of thicker nectar, richer in sugar.


In addition to sugar there are other substances in nectar. Like the power drinks used by athletes some contain ion supplements, such as potassium and sodium. Other common supplements of nectar are aminoacids, the building blocks of proteins. Let us remember that adult butterflies and moths cannot eat any solids. They have no chewing parts, only a long, thin tongue good enough for fluids and maybe the occasional pollen grain. As I mentioned before, most insects are short lived and may do fine without proteins in their diet, but the beloved monarch butterflies live for several months and have to make an arduous journey. They certainly need a well balanced diet; sugar alone would not suffice them.

There are other ingredients in nectar which I will discuss in future posts. I only want to mention here that in addition to nutrition, these substances may add flavor to this food making it more attractive to the pollinators and other flower visitors.

It is rather amazing to realize that we didn’t invent energy drinks; flowers did it millions of years ago. It gives me pause when I prepare to refill the hummingbird feeder. Are we turning our loved birds into soft drink junkies? Would they be better off without our help? I don’t feel too guilty because I know that they also feed on insects so they must be getting a balanced diet despite the empty calories at the hummingbird feeder. But, just in case, I will start growing plants for hummingbirds in my garden and cutting down on the junk food.


I can think of a few (natives only): butterfly weed, lobelia, beebalm, columbines, trumpet honeysuckle, penstemon, zinnia, nicotiana. Any suggestions?

Here is a list of “Top Ten” native hummingbird plants of the Operation Rubythroat web site.

Nectar, a drink with a zing
Nectar chemistry
Nectar, the first soft drink
Tiny treeshrews chug alcoholic nectar without getting drunk

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© Beatriz Moisset. 2012

Pollinator gardens and more

A day doesn’t go by without hearing about a new pollinator garden. It is encouraging to see the growing number of people who realize that it is important to do something for bees and all the other pollinators. We are becoming increasingly aware of their important role in the pollination of crops and wild flowers and in the maintenance of ecosystems. We know that some pollinators have been in decline for a number of years, due in part to the loss of wild flowers.

In its simplest way a pollinator garden is a wild flower garden with some adequate habitat for nesting and, needless to say, free from pesticides. Now, a group in England, called the Cooperative, is taking this a step further by developing a more systematic approach to this matter. They are creating corridors for pollinator wildlife by the name of “bee roads”. Such bee roads would provide interconnected habitats for pollinators. Habitat connectivity is very important because it prevents populations from becoming isolated and thus it help maintain the biodiversity of the gene pools (all the genes present in a population).

They are starting small but plan to expand the project with the cooperation of land owners, by providing incentives for the creation of these roads of wild flowers along cultivated fields.

You can read more here News England and watch the BBC video (if you don’t mind the brief commercial at the beginning)


I hope that this initiative will inspire people in this country to start a similar project.

More on pollinator gardens in North America:
U S Fish and Wildlife
Bee-friendly gardens
Penn State
Xerces society

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© Beatriz Moisset. 2012

Where have all the spring beauties gone?

We are studying the pollination of spring beauties. The main pollinator of this lovely early spring wildflower is a bee, called the spring beauty bee (naturally). It is a species of Andrena, small, black and slender. Like all other Andrena, it has characteristic hairy spots between the eyes. This pollinator may visit other spring flowers for nectar, but it is thought that it only gathers pollen from spring beauties. To learn more about this bee, its geographic distribution, populations and its role in ecosystems, a number of volunteers throughout the eastern United States are collecting data of its visits to spring beauties.

So, I started prospecting my favorite spots where I had found these little gems of the woods floor in previous years. I was frustrated to find lesser celandines instead. I kept walking the familiar trail, and the scene was always the same: extensive carpets of glossy dark green leaves and vibrant yellow flowers. Only here and there did I see a sprinkling of spring beauties, fresh leaves of trout lilies and a few other early flowering plants of the woods.
I must say that lesser celandines are really beautiful. No wonder why they were brought to this country as ornamentals! And no wonder why many garden centers sell them and gardeners buy them! The sinister side of this invasive beauty doesn’t seem to register in the minds of commercial centers and uninformed gardeners. But conservationists see something else. Lesser celandine is replacing some of the native plants, creating a cascade effect on the balance of nature. Native plants feed native pollinators and many other insects, which in turn, benefit other members of the natural community.



I turned my attention to lesser celandines: Do they get any visits by pollinators? Do they provide any services to the natural community?
I sat down for hours on a small picnic stool surrounded by blooming lesser celandines, camera in hand, ready to snap pictures of pollinators; hardly any came. I will continue to observe lesser celandines, but I fear that I already know the answer: specialist pollinators, such as the spring beauty bee or the trout lily bee are not likely to visit these invaders of forest and gardens, useless to them. I know that in their native land lesser celandines are visited by mutually adapted pollinators and that they provide food to some caterpillars (which in turn feed birds), but nobody seems to find them nutritious in this country.
Alarmingly, this plant is a very successful invader, with means to spread by bulbs and with the ability to sprout so early in the spring that it has a head start over the other plants in the forest. Thus a rent appears in the web of life. The more this successful invasive keeps spreading, the larger the rent becomes.

Update, April 28: Fortunately I have been seeing lots of spring beauties in other places. Let us hope that lesser celandines don't spread there too.

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© Beatriz Moisset. 2012

Death among the flowers

Pollinators have such a glamorous job. They fly from flower to flower collecting golden pollen and sweet, delicious nectar. What could be better? Indeed it is a wonderful job; but just as there are snakes in paradise, there are hidden dangers among the lovely flowers. Life can be very cruel in the garden.

Ambush bugs have a very well deserved name. They wait in hiding among the flowers. Sometimes they are very hard to spot because they hide among the petals, only their alert eyes and antennae can be seen. Their sharp beaks, loaded with poison at the ready and their powerful front legs prepared to snap with vise like action.

Ambush bug, Phymata

One sunny day I was walking in the garden enjoying the comings and goings of diligent pollinators when I spotted this little killer, a jagged ambush bug. One look at its contours renders the name self explanatory. Perhaps the jagged shape makes it hard to swallow by would be predators. It also must help on disguising its appearance.

I snapped a couple of pictures and was about to move on when I saw a bumble bee land on the flower. The next few photos were taken less than a minute later and show the fate of the unfortunate bumble bee. Had it been more careful it would have escaped his fate. The amazing thing is that there was no struggle. The venom of the ambush bug must be so powerful and fast acting that it paralyzes a victim twice the size of the killer instantly.

Male two-spotted bumble bee, Bombus bimaculatus

Being a pollinator can be a hard life. But that is the way it is for everybody out there, including the killers.

Indeed, life and death go hand in hand in the garden.
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© Beatriz Moisset. 2012