Moray Wildlife Watch
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A LARGE furry insect hovering beside the yellow flowers of birds-foot trefoil on a track across a local moor looked at first glance to be similar to the buff-tailed bumble bees that were feeding alongside it.
However, on closer inspection after following it from one clump of trefoil to the next, I noted the insect was longer than the bees and had different markings.
It had two black bands on its abdomen and narrow brownish edges to its wings in comparison to the buff –tailed bumble bees that have black bodies with yellow stripes and buff tails.
It was also a faster and more agile flier than the bees and never landed on the flowers like them but hovered by the flowers as it extracted nectar from the flowers.
After following it for a while I remembered that I had seen one of them several years ago and identified it at the time as a narrow- bordered bee hawk moth.
It was the first one that I had seen despite having wandered moorland containing birds-foot trefoil and other flowers for many years.
I had probably overlooked the moth previously because of the fact that they look superficially like bumble bees and feed along with them on the same plants.
It is thought that they have evolved over time to resemble bumble bees so that they can avoid predation from insect-eating birds that may be afraid of bumble bees because the bees’ colouration suggests they are dangerous.
It also allows them to fly and feed during the day unlike many moths that only fly at night and can be easily caught by bats.
This amazing mimicry is known as Batesian mimicry. It is named after the English naturalist Henry Walter Bates after his work on butterflies in the rain forests of Brazil.
Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at potential predators of them both.
This form of mimicry may protect the bee hawk moths in some circumstances but I know that the honey buzzard, a summer visitor to the UK, eats bumble bees when digging out their nests to obtain the larvae. Some other more common birds or large insects may also eat bumble bees.
I once found a lot of buff-tailed bumble bee carcases lying on a track in a local forest.
They had been dismembered and their thoraxes and abdomens left lying on the ground separately. Their abdomens had been emptied of their contents.
I noted a pair of stonechats nearby and wondered if they had predated the bees because they feed on quite large insects.
So despite their amazing mimicry of bumble bees the bee hawk moths may not be safe from some predators.
My own theory is that they evolved similar colours and style to the bees so that they can blend in with the more numerous bees that feed alongside them and in doing so reduce the odds of being predated.
They are also faster and more agile fliers than the bumble bees and because of this are more likely to escape from an attack by any potential predators attracted by the movement of their less agile feeding companions.
n Read Merlin’s column from his travels in Moray and beyond every fortnight in print and at www.northern-scot.co.uk
