Photos © Murdo Macdonald.

There has in the past few years been keen interest in a species of solitary mining bee in the genus Colletes in the Highlands. It has been noticed and reported by many people, and may have either become more widespread or their colonies have expanded. Certainly, it appears to have become obvious in places where it has not been known in the past 10 years.

The solitary bees form a large and varied group, but they differ from bumblebees and honeybees in having no workers - one male and one female raise their young in a single nest. Confusingly, some species - including the two Scottish species of Colletes - form large dense colonies, the insect equivalent of rookeries. These attract attention on sunny days in summer as the bees mass over their nesting area, forming a moving carpet a few cm above the sandy soil into which they burrow. An active colony is a spectacular sight, and completely harmless. The bees are not aggressive, and when they are active like that are interested only in the business of reproduction. An especially large colony near a cemetery in NW Sutherland caused much unnecessary alarm in 2003, though in the circumstances the distress of mourners was understandable.

One species, C. floralis, is very rare and is not known from the north mainland, though it occurs on some of the Hebrides. It is a UK BAP priority species - click here to view the BAP page, which has a photograph.   In 2006, new sites were found on Islay and on the mainland (Kintyre), and in 2007 it was confimed still to be present in old sites on the Ayrshire coast.  The habitat is present in W. Ross, Caithness, and Sutherland, and it is worth looking for.

The much commoner C. succinctus is widespread on the west coast and occurs from Tain eastwards (see map).   It was found for the first time on Canna, and Skye (Elgol and Orbost) in 2004, and in Caithness in 2006. In 2005, small colonies were found inland in mid-Ross, one in an old sand-quarry, one on grazed heathland, and one in a forest clearing. These finds suggest that we may have been too restrictive in our view of its habitat in the past.

The rare C. floralis is active in June and July, taking pollen particularly from umbellifers (Hogweed, Wild Carrot). C. succinctus is active about a month later, July and August. The females collect pollen from Heather, and males are often seen feeding at Ragwort. Both nest in sandy soil, partly fixed grey dunes being especially favoured. They are about 1cm long, the shape of honey-bees, brown on the thorax with neat white banding on the abdomen.

With solitary bees it is necessary to have a specimen to confirm identity, so if you think you have found a Colletes colony (or indeed any solitary bee or wasp in the Highlands or islands - there are many species and little is known about them) please collect a specimen for confirmation. Alternatively, provide a note of the site with the usual details and it can be checked out. Any Colletes colony active before mid-July may turn out to be floralis, so such reports will be especially valuable.

Any records can be reported initially by email giving date, place, six-figure grid reference and any other relevant details. Directions for sending specimens will then be provided.