bees to associate a floral scent with sugar
reward ( 11). If this deficit is prolonged by
chronic exposure, impacts on colony func-
tion will accumulate. As expected for these
brain deficits, exposed bumblebees demon-
strate reduced foraging ability ( 12) and poor
colony growth if exposure continues for
weeks ( 3, 8, 9, 12).
Neonicotinoids are not identical in their
effects. Each compound activates different,
but overlapping, neuronal populations ( 9)
and differentially affects learning ( 11), preference-seeking for a particular compound
type ( 10), and cross-sensitization, in which
heightened responses and toxicity resulting
from exposure to one compound extend to
related compounds ( 9). Therefore, the effects
of the multiple neonicotinoids found to coexist in honey by Mitchell et al. may be additive
(if they operate on the same receptor types)
or different (if they act on different receptor
types). Within an intensive agricultural system that is already depleted of natural forage
opportunities, chronic bee brain dysfunction
due to neonicotinoid exposure would be expected to decrease bee foraging performance
further. The resulting lack of incoming forage
may then limit bee fecundity.
Mitchell et al.’s study highlights two key
knowledge gaps: the risks from chronic ex-
posure to individual neonicotinoids, and
possible cocktail effects when multiple
neonicotinoids coexist. A major scientific
challenge is that hundreds of agrochemi-
cals are available to mix on site or use in-
dependently on adjacent farms. Although
this potential complexity appears to create
a scientific impasse, Mitchell et al.’s study
draws attention to two important untapped
opportunities ( 4), namely to monitor honey
contamination as an indicator of local habi-
tat contamination and to gather data on ac-
tual local pesticide application rates.
Although recording pesticide use is required in the EU (EC no. 1107/2009) and the
United States (1990 Farm Bill), it is not collated into a searchable database that might
allow correlation of pesticide use with human disease (such as incidence of chronic
idiopathic diseases) or ecosystem damage
(insect abundance and diversity) ( 13). Systematic collection of these data could provide
the statistical power lacking from existing
field studies, allowing identification of possible cocktail effects that may then be confirmed in laboratory studies to demonstrate
cause-and-effect relationships. j
1. D. Goulson, E. Nicholls, Sci. Prog. 99, 312 (2016).
2. E. A. D. Mitchell et al., Science 358, 109 (2017).
3. B.A. Woodcock et al., Science 356,1393(2017).
4. N. Tsvetkov et al ., Science 356, 1395 (2017).
5. C. Botias et al. , Sci. Total Environ. 566-577, 269 (2016).
6. M. Tomizawa, J.E.Casida, Toxicol. Appl. Pharmacol. 169,
7. M.J.Palmer et al., Nat. Commun. 4,1634(2013).
8. C. Moffat et al., FASEB J. 29, 2112 (2015).
9. C. Moffat et al., Sci. Rep. 6, 24764 (2016).
10. S. Kessler et al. , Nature 521, 74 (2015).
11. S.Piiroinen,D.Goulson, Proc. R. Soc. Biol. Sci. 283,
12. R.J.Gill et al., Nature 491, 105(2012).
13. A. Milner, E. A. Boyd, Science 357, 1232 (2017).
Negative efects on bees
Neonicotinoids impair the bees’ ability to navigate and
forage efciently. This reduces colony performance
and the pollination of crops and native plants.
Translocation through soil from other uses
into bee-visited fowers and crops
Human and bee consumption
By Wim Vassen
The nucleus of all atoms consists of protons and neutrons, and the sim- plest of all atoms, hydrogen, has just one proton. The radius of the pro- ton is very small, about 1 fm (1 fm is 10–15 m), smaller than the radius of a
hydrogen atom by a factor of 60,000. As a
proton is such a fundamental particle, much
effort is devoted to measuring its size. Since
2010, proton size has been puzzling theorists and experimentalists alike. Measuring
transition frequencies in an exotic form of
hydrogen, where instead of an electron a
muon—an elementary particle 200 times
heavier than the electron—is orbiting the
proton, a 4% smaller proton size was found
(1). The near-6s discrepancy with both
regular hydrogen spectroscopy and results
from electron-proton scattering was coined
the “proton-size puzzle” and finding a solution initiated intense scientific debate, so
far without a definite outcome (2). On page
79 of this issue, Beyer et al. ( 3) present a
measurement of the 2S-4P transition frequency in regular hydrogen, one of the lines
of the Balmer series. The value of the proton
size they deduce from their spectra agrees
with the value from muonic hydrogen spectroscopy and disagrees with most previous
measurements in regular hydrogen—and
there were many. They also find a value
for one of the most accurately determined
constants of nature, the Rydberg constant,
which disagrees with the literature value by
more than three standard deviations.
The efforts of Beyer et al. were a tour-de-force toward reaching the required accuracy. In the experiment, the frequency of the
blue Balmer-b line—a line with an inherent
linewidth of more than 10 MHz—was mea-
brings a surprise in the
search for a solution to a
LaserLaB, Department of Physics and Astronomy, Vrije
Universiteit, De Boelelaan 1081, 1081 HV Amsterdam,
Netherlands. Email: email@example.com
6 OCTOBER 2017 • VOL 358 ISSUE 6359 39
Nerve agents in honey
Bees provide services through crop and
wildflower pollination and honey production.
Neonicotinoids applied to crops are
transported in pollen and nectar back to
the bee hives, where their consumption
disrupts bee brain function.