The effects of pollen beetles on the foraging behaviour of honeybees
William D J Kirk; Mahtab Ali; Karen N Breadmore
Adults and larvae of the pollen beetle Meligethes aeneus (Nitidulidae) are abundant in flowers of oilseed rape (Brassica napus) in the UK. Their effects on the foraging behaviour of honey bees (Apis mel/ifera) were investigated in the field. Bees foraged predominantly from fully open flowers, but landed on fully open flowers containing adult beetles less often than would be expected from the proportion of flowers with beetles in them. Of 107 flowers visited by bees, 99 had no adult beetles, whereas of 100 flowers selected at random, 81 had no beetles; the difference was significant. Simulated adult beetles (black spots on the petals) deterred nectar-foraging bees from landing. Bees given a choice between flowers with four black or four clear spots and one black or one clear spot were 2.5 times and 2.4 times, respectively, more likely to visit flowers with clear spots. Flowers with real adult beetles had as much nectar as those without, so there was no evidence that the avoidance of simulated beetles was the result of a learned association between adult beetle presence and reduced nectar content. Flowers containing beetle larvae had less nectar than those with no larvae, probably as a result of feeding damage to the nectaries.