An introduction to the Northern Colletes mining bee

Monday 3rd July 2023

…blog by Sally Morris, Buglife Species on the Edge Conservation Officer, written for Solitary Bee Week 2023

To celebrate Solitary Bee Week (3-9 July), Buglife Conservation Officer, Sally Morris, introduces us to Northern Colletes, a sand dune dwelling solitary mining bee. Join us to become better acquainted with one of our Scottish neighbours.

Northern Colletes (Colletes floralis) is a medium-sized solitary bee, found in Scotland in coastal sand dunes and machair (a flower-rich maritime grassland established on wind-blown sand, found in the Hebrides). In Ireland, Northern Colletes has been found nesting in marram dunes, in sandy clays along cliffs, and even in the masonry of a bridge.

The first record of this species in the British Isles comes from south-west Scotland in July 1899, originally published under the name Colletes montanus. Today it is the only bee more widespread in Ireland than mainland Britain, with Scotland and Northern Ireland providing strongholds for this species. Whilst rare in Europe, Britain and Ireland support a significant proportion of the global population and so Northern Colletes is listed as a UK priority species.

Northern Colletes (Colletes floralis) digging © Stewart Taylor

Measuring 8-15mm long, the female and male bees emerge in June and soon mate. The males die shortly after and the females begin nesting, staying on the wing until August. Although a solitary bee, they nest in aggregations meaning they will do so in proximity to others, digging burrows up to 26cm deep. The females will line the burrow with her saliva, providing structure and an element of waterproofing. In the burrow, the female will create individual cells into which she lays a single egg. In each cell, she will provide her young with nectar and pollen, foraged from plant species such as Wild Carrot, Clovers, Wild Thyme and Sheep’s-bit. The larvae feed on the provisioned food before pupating the next year, and the cycle continues!

In the field, Colletes species are very difficult to differentiate between. Where multiple species might be found in the same area, samples must be taken for microscopic study to get identification down to species level. Northern Colletes have ginger hairs (often described as fox-coloured) on their head and upper side of the thorax with narrow white stripes on each segment of their black abdomen.

The species is vulnerable to extinction due to their restricted and fragmented populations. Populations are threatened by loss of breeding and foraging habitat due to coastal development, changes to grazing regimes and climate change. Due to this, the species was chosen as one of the 37 target species of the Species on the Edge programme.

Northern Colletes (Colletes floralis) © Steven Falk

Buglife is leading exciting work to help the Northern Colletes bee in Scotland. As part of the Species on the Edge programme Buglife is working alongside seven other conservation organisations as well as local communities to learn more about this species’ needs, abundance and distribution. Improved knowledge will help inform our conservation work, helping us to support existing populations to become more resilient into the future.

Through Species on the Edge, we aim to increase habitat connectivity, talking to partners and landowners of known sites to encourage beneficial management to maintain and enhance populations and provide safe havens. Breeding sites for Northern Colletes will also be monitored to assess the risk of dune destabilisation at colony aggregations.

Engagement with local communities will be a crucial step to protecting this species, with Buglife taking measures to raise awareness and build resilience in local organisations so that communities can deliver long-term species conservation activity. Species monitoring and surveying training will be provided to communities to ensure data can be collected beyond the end of the project, and Northern Colletes populations supported into the future.

Species on the Edge is a multi-species conservation programme of eight organisations, funded by the National Lottery Heritage Fund. The partnership consists of Amphibian and Reptile Conservation, The Bat Conservation Trust, Buglife, the Bumblebee Conservation Trust, Butterfly Conservation, NatureScot, Plantlife and RSPB Scotland. Together the eight organisations will be delivering a four-and-a-half-year programme of work to tackle the impacts of environmental change on wildlife, to benefit both nature & people. The programme has a cost of over £6.5 million, with £4m of funding from the National Lottery Heritage Fund.

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90% of bee species are solitary bees and along with other pollinating animals their hard work is responsible for at least one in every three mouthfuls we eat. However, like many species, they are under threat and need our help.

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