Pollinators and Nectar Robbers

Fig. 1. Male bumble bee stealing nectar from the spur of jewelweed

Stop, Thief! That is no way to gather nectar from a flower, mister Bumble Bee! You slashed the tip of the nectar filled spur of that jewelweed and helped yourself to the reward without paying for it (fig. 1). Take a lesson from your sister (fig. 2). She is entering the flower the legitimate way, through the front door. Once inside, she plunges her tongue into the spur to reach the nectar. At the same time her back rubs against the anthers and gets covered with pollen which she will transport to another flower. Thus, she provides a service in payment for the goods she takes.

Fig. 2. Female bumble bee entering a jewelweed blossom the legitimate way

Carpenter bee, a notorious nectar robber, on Monarda

Larceny is a fairly common phenomenon in the world of flowers and pollinators. Long throated flowers or those with spurs are burglarized regularly. Many insects are too small or their tongues are too short to reach the stored goods; so they take a shortcut. Probably, the most notorious robbers are carpenter bees. With their sharp tongues they can slash the throat of flowers such as monardas and abelias and help themselves with impunity. Sometimes bumble bees and honey bees, and even ants, can be just as bad. I invite you to observe the coral honeysuckles, columbines and monardas in your garden and look for telltale signs of criminal behavior, a distinctive scar.

Scene of the crime. Note the chewed up holes a the base of each flower

You may think that flowers are innocent victims and nothing else. They just sit there looking pretty. Could they be guilty of deceiving pollinators? The answer is: Yes, some of them do. But that is another story for another day.

Looters follow right on the heels of these criminals. Many insects that couldn’t cut their way through to the nectaries take advantage of the previous break in and help themselves. Many kinds of smaller bees exploit this opportunity.

Another carpenter bee, this time stealing nectar from columbine

Curiously, some of these little criminals may provide a service to the flower as well as a disservice. Some of them are large enough so that their back legs touch the anthers or pistil of the flower; others turn around and collect pollen the legitimate way after stealing some nectar. Still others are helpful to the flowers in an indirect way. When the legitimate pollinator arrives and finds that most of the flowers in one cluster have been looted, it abandons the site in disgust and moves on to farther patches of flowers. This results in increased cross pollination by cutting down the number of repeated visits to just one plant.

Honey bee

Ants

Small solitary bee taking advantage of a previous break in

It is significant that in this complex choreography of cooperation, deception and indirect effects the members of a healthy, well established ecosystem usually fare better than those of disturbed ones or those overrun by non-native plants.

It is fun to describe these processes using terminology borrowed from human activities. But, bear in mind that some of these terms are useful for their descriptive value and have entered the technical language: “nectar robber”, “illegitimate entrance”. Needless to say, nobody would take them literally. The language of biology is rich in words that have gone beyond their metaphorical use to serve a practical purpose. One of my favorites is “mating strategies” or “reproductive strategies”; as if a brainless plant or a lowly nematode could devise strategies.

This is why I find it incomprehensible when some people object to the words “invasive” and “invasion biology” because of their connotations. Their arguments are unconvincing. I will give up those words the day we need to give up all the other words that originated from metaphorical expressions.

© 2012, Beatriz Moisset. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. If you are reading this at another site, please report that to us