August is a fairly spectacular sight in the Peak District – up away from the arable fields, the heather turns the landscape pink and purple amongst the gritstone. Such a vast resource does not go un-tapped by the natural world and one solitary bee in particular has evolved to exploit the nectar wich underpins this aesthetic abundance.
This beautiful little solitary bee is known as the heather colletes – Colletes succinctus. These are slightly smaller than a honeybee but have a similar banded pattern to their abdomen. They are a member of the colletes family – known as the plasterer bees.
One of the first misconceptions about solitary bees is that you will find them in isolation. Where the conditions are right however, many species of these bees form dense nesting aggregations. The ‘solitary’ epithet refers to the fact that they do not partition roles in the same way as the social honey bees, such as workers and queens. As we walked the sandy soils of the National Trust‘s Longshaw Estate, we saw these little bees feeding on the heather – their bodies curled almost foetally around the flowers – and soon started spotting their nesting holes too!
At first we saw a few holes here and there, but soon we were coming across dense aggregations of the pencil-sized nesting burrows. Much to the bemusement of a group of American tourists hiking up to the tor, I spent the next 20 minutes on my knees watching their coming and going – the video below shows some their entering and leaving their nesting holes.
The males emerge a little before the females, who themselves appear in August to co-incide with the flowering of the ling. I watched the females leaving their holes and flying up to the heather in whose roots they were nesting. Here they gather nectar and also pollen to stock the larders of their nesting burrows. The females layer their burrows with pollen and then lay their eggs which overwinter as pre-adults (eggs to larvae) to emerge the following summer.
The males hang around the nesting burrows and mate with the females as they fly to and fro – sometimes a mating ball will form where several males will attempt to mate with a single female, grappling together until one wins out. I did not manage any good images of this behaviour, although I would recommend a read of Phil Gate‘s Guardian Country Diary piece which has a cracking photograph of the mating bees.
One thing which was noticable was the difficulty the bees had in keeping their footing on the loose, sandy soil. Often they would slip and fall, or otherwise engage their wings just to stay positioned on the ground. Coupled with their propensity for nesting on bare ground, an opportunity often afforded by well-walked paths, it much be a feat of engineering to maintain the integrity of these burrows in such substrate. The video below shows a couple of such incidents in slow motion:
I took a few more slow-motion videos of their flight as they enter and leave their nesting burrows. They would often land close to their burrow and the look around a while before successfuly locating their hole. I wonder how they know which is their entrance, amongst so many others. From watching other mining bees prviously, they seem to use landmarks in such a way that adding or removing something from the immediate vicinity of the entrance, such as a twig or leaf, can leave them apparently unsure about their home.
Just a few clips of them leaving in slow motion to finish off! As always if you want to find out more about a bee species in the UK, including these heather colletes, I would suggest checking out the BWARS species accounts and Steve Falk‘s Flickr page including images and the text which accompanies the images in his excellent book.