Pollinators: bumble bee

Showing posts with label bumble bee. Show all posts

Sunday, February 12, 2017

Butterfly Pollination

Fritillary butterfly on butterfly weed

When you mention pollinators to people, the immediate answer is: bees and butterflies. Bees, yes, the 20,000 species or so do a huge percentage of pollination. Some plants depend entirely on bees for this function. However, when it comes to butterflies, a different story emerges. Other insects, such as flies, wasps and moths are known to do a respectable amount of pollination, probably far more than butterflies do. Some of the mentioned insects are indispensable to certain plants, such as figs, cacao and yucca. Some flies are used in farming.

A great variety of pollinators and flower visitors

Butterflies visit flowers but that alone doesn't make them good pollinators. They are easily noticed because of their large size and color. That is why the general public takes notice, but biologists have not paid a lot of attention to the role of butterflies as pollinators. So it would be nice to know a little more about them and how much credit they deserve.

Bumble bee on Helenium

Let us compare a bumble bee with a butterfly in a field full of ragworts, for instance. Ragworts are pretty, daisy-like, rather weedy yellow flowers. A bumble bee hastily gathers pollen and nectar and moves on quickly from blossom to blossom in one plant, next it moves on to the next plant and the next, without wasting any time. It finally rushes home to feed a hungry brood with the gathered supplies. A butterfly, on the other hand, is free from family obligations. It only needs some nectar to quench its thirst so it lazily sits on a flower, unfolds its long tongue and drinks at leisure. It takes off and wanders away apparently aimlessly. Farther down it may finally land on another flower and drink some more nectar. Later on it may visit another plant a good distance from the previous ones and so on.

It is obvious that the bumble bee performs more pollination because of its diligent behavior. However, the butterfly is doing something important by transporting pollen to plants that are a good distance from each other. It is performing cross pollination and ensuring a good mixing of genes. Plants benefit from this increase in genetic diversity. Furthermore, recently researchers have learned that the pollen, stuck to a butterfly's long tongue, stays fresh for a good time and ensures this valuable pollination at a distance.

Red banded hair streak butterfly on Helenium

Butterflies seem to do more pollination in tropical regions than in temperate ones. Butterflies and hummingbirds are good at finding nectar inside long-necked or trumpet shaped flowers. They are attracted by red flowers, which are rather common in the tropics. Bees are color blind to the red color and prefer yellow and blue or purple ones. Butterflies, like hummingbirds, have a good vision for the red color.

A number of flowers are completely dependent on butterflies for pollination. Some South African orchids fall in this category. Another flower dependent on a butterfly for pollination is a member of the pea family, the Peacock Flower that grows in the Caribbean.

Orange sulphur butterfly on asters

Notice the long tongue

In summary, butterflies, while not the most efficient pollinators, are important, even essential, in some instances.

Also see:
Pollinator Foraging Behavior and Gene Dispersal in Senecio (Compositae) (contribute to cross pollination, farther distances than bumble bees)

Zebra Longwing Butterfly (Heliconius charitonia)

Fritillary: A Pretty Butterfly and a Good Pollinator

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2017

Sunday, June 19, 2016

Bees and Biodiversity

Bombus ternarius, Tricolored bumble bee on mountain mint

Recently I discussed the idea of allowing dandelions on the lawn to benefit pollinators. I pointed out that such practice only benefits a handful of generalist pollinators, but not the specialists. The latter can be more numerous than the former when they are all counted. They also account for the wide diversity of nature.

Bombus impatiens, Common Eastern Bumble Bee on blanket flower

Andrena cornelli, Azalea andrena on azalea

Let me expand on the concept of biological diversity or, as it is often called by ecologists, biodiversity. There are 4,000 species of bees in North America, from the familiar, big and plump bumble bees to tiny bee species that remain unnoticed to all except to those who study bees. Bear in mind that even bumble bees aren't just one single species but about 46 in North America.

Augochlora pura on thistle

Nomada, cuckoo bee on spring beauty

Bee species vary not only in size but in many other ways. Some are active from early spring to the end of fall. Others complete their whole cycle in just a few weeks and remain dormant the rest of the year. Some are adapted to different climates and cover a large area, others are more limited in their geographic distribution.

There are even some species, called cuckoo bees, that don't bother raising a family. Instead, just as cuckoo birds, lay their eggs in the nests of other bees.

Some bees have a long tongue that enables them to reach into fairly deep throated flowers. Others can only visit flowers that are relatively flat and open. Finally, some are very particular about the flowers they visit.They collect pollen from only one species of plants (monolectic) or a few related species (oligolectic). They may visit a wider range of flowers for nectar, but only their choice plants will satisfy their pollen needs.

Agapostemon splendens on seaside goldenrod

Lasioglossum pilosum on coneflower

Losing a few of these specialists may not be catastrophic, but it is preferable to preserve as many of them as possible. A rich variety of species confers resilience to an ecosystem. This is why it is important to have a wide range of specialists along with the handful of generalists. One way to help the specialists is to plant a variety of native plants to ensure that some of them satisfy their needs.

Colletes on Cerceris canadensis

Bombus perplexus, confusing bumble bee on common milkweed


Long horned bee on sunflower

All images © Beatriz Moisset

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2016

Thursday, September 18, 2014

Sneezeweed or Helenium

Halictid male bee on Helenium. © Beatriz Moisset

It is September, the days are getting shorter, the weather cooler. Plants put up a display that rivals or even surpasses that of spring. Asters, goldenrods, coneflowers and a number of other similar flowers create a golden explosion in gardens and meadows. Pollinators seem busier than ever, taking advantage of this bounty. Insect flower visitors love yellow and flowers seem to know it. They dress up in colors that attract their favorite visitors in the hope that they carry pollen to other flowers of the same kind. Pollinators, in turn, know that abundant resources await them in the bright yellow flowers.

Fig. 1. Three Helenium blossoms of different ages. © Beatriz Moisset

Let us look at one of these flowers in closer detail. Helenium, also called sneezeweed, has the same structure as sunflowers and asters, a crown of petals and a center made of little knobby structures called florets. Each one of those knobs is an entire flower which produces pollen and seeds. Each one needs to be pollinated in order to produce a seed. The dead heads you see later in the fall are little packages of these nutritious mature seeds that bring joy to passing hungry birds.

Fig. 2. Several Helenium or sneezeweed flowers. © Beatriz Moisset

The florets do not mature all at once. They proceed in an organized fashion from the outer ring to the center, row by row; they open and expose the pollen-carrying anthers and the pistils ready to receive pollen. They also fill up with nectar. Only one row or two at a time are ready to welcome visitors and to be pollinated. Bees know that. Even syrphid flies know that. You can see them moving from floret to floret until they complete the circle. Then they fly to the next blossom. They know enough not to waste time on the unopened flowers or the ones past their prime.

Bumble bee collecting pollen and nectar from open florets. © Beatriz Moisset

Take a look at figure 1. The sneezeweed blossom near the center is quite fresh; most florets are still closed; only one is almost ready for pollination. The one in the upper right is halfway through; there are still some rows of unopened florets to go. The one below it is approaching old age, almost all done. Now, you can look at Helenium flowers and determine their approximate age just by looking at them. What do you think about the flowers in figure 2?

Another bumble bee. © Beatriz Moisset

Smart pollinators, not only know where the food is in each flower, but also know that they will continue to find supplies in the following days. Bumble bees are known to faithfully come back to their favorite flower patches.

Sunflowers and asters do the same. See the following examples:

Agapostemon female on sunflower. © Beatriz Moisset

Sunday, January 12, 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

Sunday, September 1, 2013

Buzz Pollination of Fabaceae Flowers

Flower of Senna. Observe the pores at the tip of the anthers

It is interesting how several families of plants have evolved anthers that require buzz pollination, also called sonication, independently of each other. The organ that contains the pollen or anther of most flowers splits open when the pollen is ripe, making it available to the flower visitor. Buzz pollinated flowers do it differently. The anther remains closed, except for a pore at its tip. The only way to extract the pollen is by shaking the anther with just the right kind of vibration. Bumble bees are pros at doing this. Honey bees never developed the technique.

We are most familiar with the members of the tomato and potato family, Solanaceae. So much so, that some gardeners resort to a tuning fork or just an electric toothbrush to ensure pollination of the tomato flowers. Seeing pollen fly from the anthers during this process is a sight worth seeing. Another family with members that require buzz pollination is the Ericaceae; Blueberries, cranberries, azaleas and rhododendrons use this process.

Perhaps, it is less known that some members of the pea family, Fabaceae, in the Caesalpinioideae subfamily also resort to this process. The genera Senna and Cassia, belong to this group. Recently I observed a bumble bee visiting the bright yellow flowers of a Cassia and was able to record the buzzing. The sound is unmistakable, quite different from the buzzing of flying. Watch the video of bumble bee on Senna and pay attention to the sound. You can compare it to that of a bumble bee pollinating an azalea.

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