Research shows: commonly used pesticides make bees picky eaters and less inclined to dance

An experimental study by the University of California, San Diego found that small doses of pesticides make honeybees that ingest them become "picky eaters" and also less willing to "dance" to inform their hive mates of the location of good food sources; overall, this affects the hive's food stores and in turn affects the survival of the bees. This finding may provide part of the answer to the mystery of colony collapse.

The report on this experiment was published in the most recent issue of the Journal of Experimental Biology, and is of great significance for unraveling the mystery of the massive disappearance of bee colonies in recent years. Some earlier studies have already pointed out that pesticides are related to colony collapse, and such research should help subsequent analysis and the development of types of insecticides more suitable for bees pollinating crops.

The U.S. online media outlet Science Daily reported that since 2006, beekeepers in North America and Europe have lost one-third of their bee colonies each year, commonly known as "colony collapse disorder" (CCD), but the exact cause remains unknown to this day. Most scientists believe it is largely related to pesticides, especially the use of neonicotinoid insecticides, which has recently drawn the attention of beekeepers and scientists.

In this experimental report, biologists focused even more specifically on the neonicotinoid "imidacloprid"; this insecticide has been banned in some EU countries, and the United States is also gradually strengthening its safety review.

Imidacloprid was the sixth most commonly used insecticide in California in 2006, and in addition to agricultural use it is also used in household environments. The study's principal investigator, James Nieh, confirmed that the chemical affects bees' learning and memory; as long as bees ingest a very small amount of imidacloprid, they prefer sweeter nectar and do not take up previously collected nectar of lower sweetness, even though both are equally important nutritional sources.

When bees find a good food source, they fly back to the hive and use a "waggle dance" to inform their hive mates to go forage, but the study also found that bees that had ingested a small amount of imidacloprid also danced less often.

The researchers warn that such "picky eating" and reduced willingness to inform will greatly reduce the nutrients the bees bring back to the hive, further reducing the food stores in the hive and thereby affecting the survival of the colony. This means that a pesticide originally considered safe actually has a negative impact on the health of the colony.

To test the effect of imidacloprid on bee preferences, the researchers restrained the bees' bodies in the experiment so that they could only turn their heads; in this setup, they increased the sweetness of the water successively from 0%-50%, stimulating the bees' antennae with sweet water to observe whether their mouthparts made sucking movements. The results found that bees that had ingested imidacloprid disliked low-sweetness water more than the control group (which had not ingested imidacloprid).

Scientists also observed that bees that had ingested imidacloprid danced significantly less, roughly 1/4 to 1/10 as much as the control group, and some bees did not dance even once.

Fun Fact: The Honeybee Waggle Dance

The path of the bee's dance forms a figure eight. The outer looping portion is called the return phase; the straight portion in the middle is called the waggle phase, which is how the waggle dance got its name. The bee waggles its abdomen as it walks along this straight line; the duration of the waggle indicates the distance to the food, and the longer the waggle, the farther away the food is, with 75 milliseconds representing 100 m. The angle between this straight line and the direction of gravity represents the angle between the direction of the food and the direction of the sun. It was later discovered that bees will correct the angle of the straight line according to the relative movement of the sun's position. (Source: Wikipedia)

* References: Science Daily news report, Wikipedia

* This article was originally published by Environmental Information Center