Signs of Summer 4: More on Bees

Imidacloprid (a neonicotinoid). Drawing by Monolemma, Wikimedia Commons

(Click to access an audio version of this blog!)

Neonicotinoids are a group of insecticides that are molecularly similar to nicotine. Nicotine itself is produced by a wide variety of plants including tobacco (in very high levels) and tomatoes and potatoes (in very low levels). In these plants the ecological purpose of the nicotine is to act as a protection against insect herbivory. Nicotine is, then, a “natural” insecticide. Synthetic neonicotinoids were produced commercially starting in 1985 and were approved for use in United States in 2003. These chemicals were rapidly incorporated into our agroecosystems and by 2013 were being used to control insects on almost all corn grown in the United States and also most of the cotton, sugar beets, and sorghum. Soybeans, rice, fruits and vegetables have also extensively been treated with neonicotinoids.

Neonicotinoids and their breakdown products, compared to carbamate and organophosphate pesticides, are less toxic to vertebrates (mammals and birds) but have been correlated with serious, non-target impacts on a variety of insects including pollinators like honeybees and bumblebees. These impacts of neonicotinoids led to a discussion among EU countries about the safety of these pesticides (see Signs of Summer 11, July 27, 2017). Finally, on April 27, 2018 the EU voted to ban the use of three of these neonicotinoid pesticides in any open agricultural field. They cited overwhelming evidence that linked these three pesticides to declines in pollinators, butterflies, aquatic insects and insect eating birds. Similar restrictions and bans have been proposed in the U.S. Congress, but no action has yet taken place.

Honeybees, Public Domain, Pixabay

A study recently published in Current Biology (March 22, 2018) examined how honeybees and bumblebees metabolize two of the neonicotinoid pesticides. One of the chemicals in the study was imidacloprid which is a particular toxic neonicotinoid and one of the three that was banned for use in open fields in the EU zone. The other was thiacloprid which is a much less toxic neonicotinoid and one that is has not been banned for use in agricultural fields in the EU zone.  Researchers found that in honeybees a cytochrome P450 protein system rapidly broke down the thiacloprid into substantially less toxic compounds. These bees, then, were able to survive in environments in which the thiacloprid was used to control pest insects. Bumblebees used a different protein system to break down the thiacloprid but achieved similar tolerances to it. The imidacloprid, on the other hand, was not metabolized into less toxic products by either honeybees or bumblebees. Both honeybees and bumblebees, then, were significantly harmed in environments in which imidacloprid was used.

Field studies in which multiple pesticides and fungicides are combined (a condition that more closely replicates actual chemical conditions of treated agricultural ecosystems) are being conducted. It is significant, though, to recognize that not all neonicotinoids affect bees in the same way. The banning of the most lethal of these chemicals should be a goal for all concerned individuals and institutions.

Honeybee waggle dance. Photo by Tautz and Kleinhenz, Wikimedia Commons

The “waggle dance” is one of the best known and one of the most carefully studied systems of communication among individuals of an invertebrate species. Honeybees are able to communicate to their hive mates via a series of dancing body movements the locations and distances of pollen and water sources and initiate a mass flight of the hive’s workers to gather up these important resources. A study at the University of Tokyo (published in Entomological Science on November 5, 2017)  describes a new version of the waggle dance that communicates both a danger to the hive (in the form of attacking wasps) and a call to protect the hive (via the gathering of odorous plant materials (like the leaves of Nepalese smartweed) which is then spread across the entrances to the hive in order to repel the wasps). This new waggle dance is referred to as the “war dance” of the honeybee!

And, finally, bees have been added to the very select group of animals (that include humans, non-human primates and the African grey parrot) that can comprehend the concept of “zero.” In an incredibly elegant experiment neuroscientists at the University of Melbourne in Australia and in the Universite de Toulouse in France trained bees to choose pieces of paper that had the fewest number of black dots in order to get a reward of sugar water. Once the bees were trained to choose the paper with the smaller number of dots, they were then given the choice between a piece of paper with one dot and a piece of paper with no dots. These bees chose the blank sheet pf paper 63% of the time thus demonstrating that they recognized that zero dots were less than one dot.

Possibly bees have evolved the ability to notice the absence of something in order to more efficiently forage or avoid predation. Perhaps there are other explanations for these amazing observations. As the old joke goes: to whomever invented the zero ….. thanks for nothing!

Photo by D. Sillman

And a quick update on my mason bees! I have over one hundred sealed nesting tubes in my “bee basket” and cylinders. The bees were incredibly active for just over five weeks. Along with the forsythia (which had just started to flower when the bees first emerged) daffodils and hyacinths and early clover all flowered during the bees’ active period and provided them, I am sure, with abundant pollen and nectar. Now I wait until next spring! Mason bees are fun pets!


This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *