Imitation is the Best Form of Protection in Some Cases

Not a bee, but a mimic, the fly Eristalis. © Beatriz Moisset

A stroll among the flowers allows me to see numerous bees of different sorts, zipping along from blossom to blossom. Just as numerous are other winged insects that look very much like bees. The experienced eye recognizes them for what they are, flower flies impersonating the stinging insects. But those unfamiliar with bees or with insects, in general, may assume that these flower flies are bees. They may even recoil in fear of a sting although the flies are innocuous, lacking such powerful weapon.

A wasp mimic, Spilomyia sayi © Beatriz Moisset

Those flies who imitate bees or wasps have a reason for playing this masquerade. They are not interested in fooling us, humans. Their deception is aimed at their predators, mostly birds. However, the ruse is so effective that it even we fall for it.

Syrphid flies, also known as flower flies or hover flies, are almost as assiduous in visiting flowers as bees are. They drink nectar and sometimes also feed on pollen. Although not as efficient as bees as pollinators, they deserve some credit and occasionally their contribution to pollination is significant. Another group of flies that visit flowers with great frequency includes the so called bee flies.

Both, flower flies and bee flies mimic bees or, in some instances, wasps. The imitation is very specific in some cases. The so called drone fly, Eristalis tenax, looks like a honey bee. The name is appropriate, considering that male honey bees, drones, have large eyes, and these flies have even bigger eyes. Both, the fly and the honey bee are European. The imitator evolved along with its model in that continent. Another European flower fly that mimics honey bees effectively is the narcissus fly, Merodon equestris.

Other flower flies and also a robber fly imitate bumble bees. They have a furry coat and even buzz like bumble bees.

Bumble bee mimic, Mallota bautias © Beatriz Moisset

The smaller flies, members of the Syrphinae subfamily apparently are mimics of some or another of the many solitary bees. In most cases one cannot be sure of the model chosen for this mimicry.

A honey bee, the model for many mimics © Beatriz Moisset

It is a peculiar thing that some imitations are extremely good, while others are rather general in character. Biologists speculate that even a not-so-good imitation may serve the purpose of deceiving the enemies and this is why such types of mimicry persist in nature. It is also possible that the predators don’t see exactly what we see and the mimicry is convincing enough for them.

This is just one type of mimicry. Other insects take the appearance of their surroundings, which makes them nearly invisible. Still others look like bird poop, not an appetizing sight for a snack seeker. Stay tuned for descriptions and illustrations of more of these ingenious survival mechanisms.

References

http://pollinators.blogspot.com/2014/07/the-great-impersonators-flower-flies.html

https://polinizador.wordpress.com/2011/07/11/mimics-of-bumble-bees/ 

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2015

The Most Invasive Butterfly: Cabbage White Butterfly (Pieris rapae)

A flock of cabbage butterflies

(Pieris rapae)

© Beatriz Moisset

If you see a pretty white butterfly, more likely than not you are seeing an invasive species that was accidentally introduced to this country and to many other parts of the world more than a century ago.

The cabbage white butterfly is noticeable, pretty and soft, it visits gardens, meadows, you name it. Perhaps the only places beyond its reach are higher elevations. It starts flying early in the season and produces several generations throughout the summer and fall. No wonder it is seen so often.

Cabbage butterfly

(Pieris rapae)

© Beatriz Moisset

The name refers to the plant its caterpillar feeds on, cabbage. It also eats other members of the mustard family, such as cauliflower and kale and it is regarded as a serious pest. It also feeds on a number of wild, non cultivated mustards, including the invasive garlic mustard.

The cabbage butterfly is related to a group of native butterflies, the so called whites, yellows and sulphurs or family Pieridae. Their colors, as the names indicate are either whites or yellows. The caterpillars of most of them also feed on plants of the mustard family. A total of 58 species lived in North America before the arrival of this newcomer. Nowadays, the cabbage white is seen as often as all of them combined. One wonders if the growing numbers of this invader are having an impact on the populations of native Pieridae butterflies.

Orange sulphur butterfly

(Colias)

© Beatriz Moisset

In summary, it has the qualities of so called weedy species, with high rates of reproduction, very adaptable to different food sources and a variety of habitats.

Virginia white butterfly

Pieris virginiensis

© Beatriz Moisset

The cabbage butterfly reminds me of several insect species that were brought to this country intentionally or accidentally and proceeded to become incredibly widespread in a relatively short time. Now, some of them are more abundant than any of their native relatives. Here are a few examples: the Asian ladybug, the Chinese mantis, the giant resin bee, the European paper wasp, the drone fly, and the brown marmorated stink bug.

David Quammen, a distinguished journalist who has written extensively on conservation and ecology, has coined the term “Planet of Weeds,” meaning that the ecological changes caused by humans are having a severe impact on the flora and fauna of the entire planet. We had transported unprecedented numbers of species of plants, animals and bacteria beyond their natural distributions with the consequence that many of them have become established in their new surroundings. Not only do they become established but spread out from the original place of introduction, thus deserving the name of invasive species. They impact the local flora and fauna, bringing up the extinction of many species. In this way we are causing a mass extinction, comparable to some of the most serious mass extinctions of the past.

Specialist species are more vulnerable to extinction. The ones that have the best chance for survival are the weedy ones, the adaptable generalists. We are creating an impoverished world, gradually losing precious biological diversity, biodiversity for short. It may take millions of years for this biodiversity to raise back to the present levels. The human species may never see that.

Drone fly (Eristalis tenax)

One of many introduced, widespread species

© Beatriz Moisset

List of articles

Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2016

Mass Appeal and Pollination

Some of the many visitors to goldenrod.  © Beatriz Moisset

Many flowers are not particularly selective; they welcome all kinds of visitors. They are wide open, easily accessible, thus many insects can reach the nectar and/or pollen regardless of whether their tongues are long or short. Such flowers provide a convenient standing platform to save their visitors the inconvenience of hovering over them. Their structure is simple so the pollinators don’t need to figure out how to open them in order to reach their rewards. Goldenrod is a fine example.

Monarch butterfly on goldenrod. © Beatriz Moisset

 I have spent countless happy hours observing goldenrods and photographing their numerous visitors. The one most common in my area is the Canada goldenrod. Several hundreds of species visit their flowers. Bear in mind that not all flower visitors qualify as pollinators. Some are not efficient at carrying pollen, or sit in one place for a long time and never make it to another plant. Such is the case of ambush bugs, whose only concern is to snare hapless pollinators to make a meal out of them. If you are interested on photographing and identifying pollinators this is a good place to start.

Metallic green bee. © Beatriz Moisset

 This plant blooms in the fall. It often gets blamed for allergies, but the real culprit is another plant that grows close by, sometimes intermingled with goldenrods, ragweed. Its flowers are inconspicuous because its pollen gets carried by the wind, not by officious pollinators. This is how it gets into our nostrils and causes our suffering. The much maligned goldenrods have larger, heavier and stickier grains of pollen that cannot get airborne and that require help from visitors.

Two states, Kentucky and Nebraska, have the goldenrod as their state flower. It is not clear which species of goldenrod Kentucky picked, but it is likely the Canada goldenrod (Solidago altissima). Nebraska’s choice is clearer, the giant goldenrod (Solidago gigantea). South Carolina, not satisfied with a state flower, also has a state wildflower. It is the Canada goldenrod. It is worth mentioning that Delaware has a state herb, the anise-scented or sweet goldenrod (Solidago odora).

Bumble bee on sunflower. © Beatriz Moisset

Coreopsis. © Beatriz Moisset

 Two other state flowers also have mass appeal. Like goldenrod, they are members of the daisy or aster family, easy to access by different kinds of visitors. They are Kansas’ sunflower (Helianthus annuus) and Maryland’s Black-eyed Susan (Rudbeckia hirta). It is worth mentioning here that two states, Florida and Mississippi, chose the tickseed (Coreopsis spp.) as a state wildflower in addition to their official state flowers, the orange blossom and the magnolia, respectively.

Kentucky: Goldenrod

Nebraska: Goldenrod

South Carolina (wildflower): Goldenrod

Delaware (herb): Goldenrod

Kansas: Sunflower

Maryland: Black-eyed Susan

Florida (wildflower): Coreopsis

Mississippi (wildflower): Coreopsis

The indiscriminate pollination strategy represented by all these flowers has advantages and also disadvantages. They suffer no shortage of pollinators. If one species is doing poorly one year, as it often happens in the insect world, there are plenty more to fill in the deficiency. However, sometimes too much of a good thing can be bad. Some of these non-specialized pollinators may be visiting a variety of flowers instead of being faithful to just one species so they end up carrying the wrong kind of pollen in such cases.

Blossoms with such mass appeal give me the opportunity to introduce the reader to the main groups of pollinators. They are all well represented on these mass appeal flowers.

Andrenidae bee © Beatriz Moisset

Bumble bee. © Beatriz Moisset

 Let us start by getting acquainted with bees. More than 80 species have been seen on goldenrods. Some of them deserve mention. Bumble bees are larger than other bees, plump, dark with yellow or white stripes, and hairy. Metallic green bees are small and gorgeously colored. They may escape notice if one isn’t very observant; but it is easy to become captivated by their shiny aspect. Mason bees and leaf-cutting bees carry pollen on their underbelly, unlike most other bees that carry it on their hind legs. Most of them are dark, nearly black and about the size of honey bees or slightly smaller.

Wasp. © Beatriz Moisset

 Wasps are related to bees and sometimes people confuse them. Most wasps are less hairy than bees and have narrow waists. They raise their young on a diet of insects or spiders, instead of pollen and nectar as bees do. Adult wasps need nectar to fuel their flight. Thus, they are frequent flower visitors and accomplish some pollination.

Syrphid fly. © Beatriz Moisset

Syrphid fly. © Beatriz Moisset

Many types of flies, including mosquitoes and gnats visit flowers to feed on their nectar. Some are good pollinators. The Syrphid flies, also called flower flies, are among the most assiduous flower visitors. Most of them mimic bees or wasps and are frequently mistaken for them. However, they don’t sting and there is no reason to fear them.

Buckeye butterfly on goldenrod. © Beatriz Moisset

Pyrausta moth on sunflower. © Beatriz Moisset

Yellow collared scape moth on goldenrod. © Beatriz Moisset

 Butterflies, skippers and moths have extremely long tongues that they can use like drinking straws when sipping nectar. They favor long necked flowers and carry pollen from one to another.

Polished lady beetle on sunflower. © Beatriz Moisset

Soldier beetle on goldenrod. © Beatriz Moisset

Finally, beetles, although not well specialized for pollination, are also capable of doing so in special circumstances. We already mentioned magnolia pollination by beetles. They also visit other flowers and can do a reasonably good job in some cases.

In the following chapters we’ll see flowers that have chosen a different strategy. They are pickier or more selective. Some attract a handful of visitors; a few go to the extreme of having relationships with only one species of pollinators.

Pollinators of Official State Flowers

References

Goldenrods and Asters: Great PollinatorPlants for the Fall. Penn State Extension

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2015

Blowflies are Pollinators Too

Mating Lucilia flies. © Beatriz Moisset

A bright metallic green insect lands on one of the flowers in your garden. It has large red eyes. Aside from the interesting colors, it looks like a plump house fly. You can't decide whether you like it or not. Its scientific name is Lucilia, its common one is greenbottle blowfly. It is unusual for a scientific name to be prettier than the common name. You dislike the common name even more when you find out its meaning. According to the Free Dictionary a blowfly is "any of several flies of the family Calliphoridae that deposit their eggs in carcasses or carrion or in open sores and wounds." Carrion? Open sores? Definitely not pretty.

Lucilia on common milkweed. © Beatriz Moisset

So, it is agreed, Lucilia is an ugly fly despite its startling colors. But, does it have some redeeming features? Fortunately, it does. Its habits are put to full advantage in forensics. By examining the Lucilia's maggots found in a corpse it is possible to determine the time of death. Another use is in medicine. This may cause you some revulsion, but it isn't as bad as it seems. Open wounds that don't heal and begin to accumulate dead tissue can be cleaned up by blowfly larvae. Let me clarify that only maggots raised in perfectly sterile conditions are used for this purpose. The larvae feed only on the dead cells and leave the healthy tissue untouched. This method is superior to that of the most expert scalpel held by a surgeon.

© Beatriz Moisset

But this is a blog about pollinators, so let us get into this subject. Blowflies, Lucilia in particular, are good pollinators of certain flowers. You see them frequently visiting a variety of blooms in your garden. They are more efficient than bees in pollinating onions and cabbages. I wonder why they show such preference for plants so notorious for their strong odor. Perhaps there is a connection between these plants' fragrance and that of smelly dead things fowever I haven't found any references so far. Most pollinators don't fair well in greenhouses. Lucilia, on the other hand, is easy to raise and to maintain in these conditions, so this is the preferred pollinator of the mentioned plants.

Two Lucilia flies pollinating Allium. © Beatriz Moisset

In summary, blowflies aren't that bad at all. In fact, they are so beneficial that we may begin to see their beauty. Let us welcome them in our gardens.

Lucilia on mountain mint. © Beatriz Moisset

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

See:
Onion pollination by blowflies


© Beatriz Moisset. 2014

The Great Impersonators, flower flies

Eristalis tenax, the drone fly, a honey bee mimic

© Beatriz Moisset

Why would one insect want to look like another? There must be some advantage in doing so. When it comes to flower flies the answer becomes apparent after a little observation.

These flies are found visiting flowers rather than garbage or dead meat like some of the flies you are most familiar with. They are rather pretty, with patterns of brown and yellow or black and yellow which easily remind you of bees. I have seen many a photographer deceived to the point of posting a picture of a flower fly claiming that it is a bee.

The goal of this remarkable imitation is not to fool photographers, of course, but rather hungry predators. Flower flies are delicious morsels of food that any bird would readily accept, but the fear of being stung by this bee mimic may lead him to think twice and skip this prey.

Some flower flies are about the size of a honey bee. The mimicry is so convincing that one of them is called the drone fly. Others are smaller and they may be imitating some of the lesser known and very abundant solitary bees. A few are long and thin and look like wasps, rather than bees.

Mallota bautias, a bumble bee mimic

© 2005 Beatriz Moisset

They can be distinguished from bees or wasps by the number of wings. Bees and wasps have four; flies have only two. The back wings have been reduced to little knobs, called halteres, used for balance. The halteres and the number of wings are hard to see when the insect is flitting about. Even when it rests on a flower, you continue to have trouble because a bee's front and back wings hook up appearing like a single unit.

Flower fly (left), bee (right)

Compare the size of the eyes

and the size and placement of the antennae

© Beatriz Moisset

Other differences are more obvious if you train your eye to see them. Flower flies have enormous eyes and tiny antennae that emerge from the front of the head, rather than higher up as in bees. Also flies are almost hairless and their legs are skinny when compared with those of bees. I hope all this helps you and saves you from embarrassing mistakes. I have seen business cards, article illustrations and even a book cover with a fly passing for a bee. So, if you still don't get them right, at least remember that you are in good company.

Toxomerus, mimics of small native bees

© Beatriz Moisset

In England, flower flies are called hover flies, an excellent description of their behavior. Some people in the US are adopting this name, so you may find either term in the growing literature on these interesting and useful insects.

A colorful flower fly

Helophilus, the sun lover

© Beatriz Moisset

These flies feed on nectar; sometimes they also eat pollen, especially the females who need this protein-rich food to produce eggs. This is why they spend so much time visiting flowers. Because of this habit they often end up carrying pollen from one blossom to another. They may not be as good pollinators as bees, but their role is not insignificant and deserves recognition. For instance, the so called drone fly is used to pollinate greenhouse sweet peppers.

Spilomyia sayi, a wasp mimic

© Beatriz Moisset

Let us applaud the bee impostors, flower flies or hover flies, for their role as pollinators.

For more on pollinators and other flower visitors read the e-book:
Beginners Guide to Pollinators and Other Flower Visitors

List of articles

© Beatriz Moisset. 2014

The Importance of Native Pollinators

Bumble bee visiting a sunflower. © 2010 Beatriz Moisset

At the risk of repeating myself, I want to discuss once again the widespread erroneous belief that we depend entirely on honey bees for the pollination of one third of our food and that we would all die if they were to disappear. Honey bees are not the only pollinators. We must value all the others and we should learn to take advantage of them for our crops' pollination.

We must remember that 4,000 species of native bees populate this country; 20,000 the entire world. They vary in size, appearance, season of activity, flower preference. . .  Some live in colonies similar to those of honey bees, but most are solitary and nest in holes in the ground or in hollow tubes inside soft pitted canes or in holes left behind by beetle larvae.

All of them combined are tremendously important, not just for the pollination of wild flowers but also of some crops. In fact, all the crops pollinated by honey bees could be taken care of by one or another of the numerous species of wild bees.

A few examples of the marvelous things native bees do

*Bumble bees and several solitary bees pollinate tomatoes, peppers and eggplants. Only they know how to manage their flowers. Honey bees cannot do it

*The alfalfa bee and the alkali bee pollinate 80% of the alfalfa flowers they visit. Several bumble bees do just as well. The batting average of honey bees is a mere 20%

*A single southern blueberry bee can pollinate $20 worth of blueberries (probably more at current rates). Honey bees don't come even close

Osmia  sp., a mason bee. © 2007 Beatriz Moisset

*An acre of apples can be pollinated by 250 female orchard mason bees. This task would require 1.5 to 2 honey bee hives—approximately 15,000 to 20,000 bees

Squash blossom. © 2014 Beatriz Moisset

*Squash bees are up early in the morning, when squash flowers are at their peak. Later on, when bumble bees and honey bees arrive, most of the pollination has already taken place

*When the weather is bad, too cold or wet, some native pollinators go out anyway. A few work before sunrise or after sunset. The honey bees prefer to stay home under these conditions

An assortment of pollinators provides a degree of insurance. When the population of one species  declines, as it is bound to happen some years, other species take over the slack. This is one of the advantages of diversification. We have depended for too long on just one species.

Despite the advantages of this variety of native pollinators, farmers often resort to honey bees because the wild pollinators are, well, wild, not easily controlled. Honey bees provide a large task force that can be managed and transported where needed. They are perfect for large monocultures, with only one kind of food temporarily available and nothing else the rest of the year.

We shouldn't ignore the contributions of native bees. They can do a superb job at small or medium sized farms. Managing them would require a healthier habitat and less pesticides. A polyculture, the opposite of a monoculture, would also be important.

We are reaching a point in which we cannot rely entirely on just one species of pollinator. The task of changing cultivation practices is huge but it can be done and it needs to be done. The Xerces Society and some universities are committed to developing the ways of putting native pollinators to good use. The results have been highly encouraging.

Long-horned bee on sunflower. © 2007 Beatriz Moisset

 

Additional readings

One Bite our of Three
Don't Underestimate the Native Pollinators

Will We all Die if Honey Bees Disappear?

Bring Back the Native Pollinators! We need them more than Ever

Farming with Pollinators, the Xerces Society
Wild Pollinators, Agriculture’s Forgotten Partners. WildFarm Alliance
Native Pollinators. Wildlife Habitat Council

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014 

Beginners Guide to Pollinators

Read the review by Kathy Keatley Garvey at the Bug Squad website, For Beginners, a Guide to Pollinators

So many flowers.  So many pollinators. So many floral visitors.
On every field trip, we see something new and different.
With so much interest in pollinators, it's good to see that biologist Beatriz Moisset has written a downloadable book, "A Beginners Guide to Pollinators and other Flower Visitors." It's meant for young adults and beginners.

Beginners Guide to Pollinators and other Flower Visitors available at:

Barnes & Noble
Lulu.com

iTunes
Amazon 

One Bite out of Three

Megachilid or mason bee, often used to pollinate fruit trees.

© Beatriz Moisset

We frequently hear that "one bite out of three comes to you courtesy of pollinators." Other times we hear it expressed as "one bite out of three comes to you courtesy of bees," implying that the bees in question are honey bees. Where did these statements originate? How well documented are they? It all sounds plausible but I hesitate to cite numbers without certainty when I give presentations about pollinators.

Fortunately a group at the University of California at Berkeley decided to get to the bottom of it. I am happy to tell you that they found the first statement to be fundamentally accurate.

Claire Kremen, one of the coauthors of the study and member of the Committee on Status of Pollinators, summarizes the results of their 2006 study as follows: "Out of the 115 crops studied, 87 depend to some degree upon animal pollination, accounting for one-third of crop production globally."

Now, I can relax and go on telling my audiences that pollinators are responsible for one third of our food. I can also face the second claim, "one bite out of three comes to you courtesy of bees." This claim originates from the confusion between pollinators, bees in general and honey bees, and it is not accurate. Some information is in order.

Augochlora pura bees.

© Beatriz Moisset

Honey bees are the most important pollinators of agricultural crops. They excel at pollinating a number of fruit trees such as apples, pears, peaches and almonds. But they are not alone in this task. We owe a lot to all the other carriers of pollen, 20,000 species of bees (4,000 in North America alone) and an assortment of wasps, moths, flies and even bats.

Anthophorini bee. It pollinates several crops.

© Beatriz Moisset

Let us look at crops pollinated mostly or entirely by non-honey-bee pollinators. Alfalfa is the most important one that comes to mind. No, we don't eat alfalfa but cows, sheep, goats and even chickens do. Without alfalfa these animals would be severely malnourished; they may not even survive. Most alfalfa growers use the services of bumble bees, alkali bees and alfalfa bees or a combination of the above plus a few other bees. These insects are well adapted to the structure of alfalfa flowers and handle them efficiently. Honey bees, on the other hand, are not fond of these blossoms and do a poor job. It may take several honey bees to do the job of one alfalfa bee; but they make up in numbers what they lack in finesse. This is why they are used in large alfalfa fields where there is no habitat left for other bees, particularly in California.

When New Zealand ranchers started raising cattle, they also needed to grow clover for cattle feed. They had to purchase seed from abroad every year because the plants failed to set seed for lack of pollinators. European bumble bees were imported to do the job, and in fact they promptly took care of the problem. Notice that it was bumble bees rather than honey bees which were counted for this mission.

Bumble bee buzz-pollinating azalea. © Beatriz Moisset
See video

The flowers of tomatoes, eggplants, peppers and other members of the potato family require special handling by the pollinator, a process called buzz pollination. Bumble bees and other native bees do this efficiently. Honey bees cannot, do not perform this maneuver. For a brief explanation of buzz pollination see: Buzz Pollination by Sue Rosenthal.

Blueberries and cranberries are mostly buzz pollinated. Unfortunately, large fields of these crops provide no habitat for the native bees and bumble bees which are most adept at this task. Under these circumstances, honey bees are used as pollinators despite their poor performance.

Yucca moth, a highly specialized pollinator. © Beatriz Moisset

Figs are pollinated by fig wasps, yucca by yucca moths, and mangoes by bats. A few other specialty crops use the services of specialized insects. Several species of flies are used to pollinate some crops such as onions and cabbage. Honey bees, or even other bees are not involved here, either.

In summary, we must remember to give credit to all pollinators. Let us thank them all. My favorite one is not a honey bee, not even a bee. It is the little fly, or midge, that pollinates the cacao flowers. What would the world be without chocolate?

Importance of pollinators in changing landscapes for world crops

List of Articles 
Also, see Bees and Vitamins. The importance of pollinators goes beyond the "one bite out of three" to our basic nutrition needs.
Update to pollinators and vitamins: Contribution of Nutrients by Pollinators
One Bite out of Three and Wildlife
One Bite out of Three before Columbus

Beginners Guide to Pollinators and Other Flower Visitor

© Beatriz Moisset. 2013