To establish whether imidacloprid, a systemic
neonicotinoid and insect neurotoxin, harms individual bees when ingested at environmentally realistic
levels, we exposed adult worker bumble bees, Bombus terrestris L. (Hymenoptera: Apidae), and honey
bees, Apis mellifera L. (Hymenoptera: Apidae), to dietary imidacloprid in feeder syrup at dosages between
0.08 and 125 g l−1. 

Honey bees showed no response to dietary imidacloprid on any variable that we
measured (feeding, locomotion and longevity). In contrast, bumble bees progressively developed over
time a dose-dependent reduction in feeding rate with declines of 10–30% in the environmentally relevant
range of up to 10 g l−1, but neither their locomotory activity nor longevity varied with diet. 

To explain their differential sensitivity, we speculate that honey bees are better pre-adapted than bumble bees to
feed on nectars containing synthetic alkaloids, such as imidacloprid, by virtue of their ancestral adaptation
to tropical nectars in which natural alkaloids are prevalent. We emphasise that our study does not suggest
that honey bee colonies are invulnerable to dietary imidacloprid under field conditions, but our findings
do raise new concern about the impact of agricultural neonicotinoids on wild bumble bee populations.

Cresswell, etc. (2012). Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid). Zoology. Volume 115, Issue 6

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