title: Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid).
abstract: Currently, there is concern about declining bee populations and the sustainability of pollination services. One potential threat to bees is the unintended impact of systemic insecticides, which are ingested by bees in the nectar and pollen from flowers of treated crops. 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 125μg 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 10μg 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.
authors.affiliation: Biosciences, College of Life & Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, United Kingdom. j.e.cresswell@ex.ac.uk
authors.forename: James E
authors.initials: JE
authors.lastname: Cresswell
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Page
authors.forename: Mehmet B
authors.initials: MB
authors.lastname: Uygun
authors.forename: Marie
authors.initials: M
authors.lastname: Holmbergh
authors.forename: Yueru
authors.initials: Y
authors.lastname: Li
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Wheeler
authors.forename: Ian
authors.initials: I
authors.lastname: Laycock
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Pook
authors.forename: Natalie Hempel
authors.initials: NH
authors.lastname: de Ibarra
authors.forename: Nick
authors.initials: N
authors.lastname: Smirnoff
authors.forename: Charles R
authors.initials: CR
authors.lastname: Tyler
mesh_terms: D000818:Animals; D001516:Bees; D005247:Feeding Behavior / Q000187:drug effects*; D007093:Imidazoles / Q000009:adverse effects*; D007306:Insecticides / Q000009:adverse effects*; D008124:Locomotion / Q000187:drug effects*; D008136:Longevity / Q000187:drug effects*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000009:adverse effects*; D057048:Plant Nectar
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D057048:Plant Nectar; C082359:imidacloprid