Bumblebees could be shrinking because of exposure to a widely-used pesticide, a study suggests.
Experts fear smaller bees will be less effective at foraging for nectar and carrying out their vital task of distributing pollen.
Scientists in the UK conducted laboratory tests which showed how a pyrethroid pesticide stunted the growth of worker bumblebee larvae, causing them to hatch out reduced in size.
Pyrethroid pesticides are commonly used on flowering crops to prevent insect damage.
The study, the first to examine the pesticides' impact across the entire lifecycle of bumblebees, tracked the growth of bee colonies over a four month period.
Researchers exposed half the bees to a pyrethroid while monitoring the size of the colonies as well as weighing individual insects on micro-scales.
They found that worker bees from colonies affected by the pesticides over a prolonged period grew less and were significantly smaller than unexposed bees.
Findings from the study, funded by the Natural Environment Research Council (Nerc), appear in the Journal of Applied Ecology.
Currently a Europe-wide moratorium on the use of three neonicotinoid pesticides is in force because of their alleged harmful effect on bees.
As a result, the use of other types of pesticide, including pyrethroids, is likely to increase, say the researchers.
Colony growth and reproductive output were monitored for up to 14 weeks.
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