Sunday, February 12, 2017

Butterfly Pollination

Fritillary butterfly on butterfly weed
© Beatriz Moisset
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
© Beatriz Moisset
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
© Beatriz Moisset

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
© Beatriz Moisset
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
© Beatriz Moisset

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)