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Some Rare Caithness Bees It would be good to follow up the interest that was shown in the field day run by Gill Nisbet and myself in August last year with a reminder of the key species that we want to know about in Caithness. Prime among these is the Great Yellow Bumblebee Bombus distinguendus, a very scarce species on the UK BAP priority list. It hangs on precariously in Caithness and Sutherland, its last mainland locations (see map). I would be very pleased if Caithness Field Club members were able to find additional sites for this bee, especially inland. It is mainly a coastal species, with sites in Caithness at John o’ Groats, Dunnet Head, Dunnet Bay and Scrabster (between the lighthouse and Holborn Head). In 2003, we found it in two more inland sites - Nybster and Westerdale - and it is likely that it occurs sparsely inland throughout the county. Queens can be found in June and July foraging mainly at Marsh Thistle or Red Clover. They are, given a good view, unmistakeable. Approaching 2cm in length, the queen Great Yellow Bumblebee is identified by its uniform yellow-brown abdomen with no contrasting patches or bands, and the thorax of similar colour but with a clear band of black hair joining the wing-bases. The abdomen shows some faint dark banding, caused by the black skeleton showing through the hair coat, but is not produced by black hairs. If you can answer ‘yes’ to all the following questions, you will have the right beast:
It is important to check both thorax and abdomen, as other species are similar in one or other pattern, but only the Great Yellow has this combination. It is also important not to pay too much attention to the common name - other species can be just as great, and even more yellow! Please look at patches of Red Clover anywhere, or Marsh Thistle on the cliffs, as you walk or drive around, and send records (with date, place, 6-figure NGR, and forage plant) to me at the address below. The other species of interest is a solitary bee - or rather two similar species. The solitary bees form a large and varied group, but they differ from bumblebees in having no workers - one male and one female raise their young in a single nest. Confusingly, some species form large dense colonies, as do the two species of Colletes mining bees. These attract attention on sunny days in summer as they mass over their colonies forming a moving carpet a few cm above the sandy soil into which they burrow. One of these bees, C. floralis, is very rare and not is known from the north mainland, though it occurs on some of the Hebrides. The habitat is present in Caithness, and it is worth looking for. The much commoner C. succinctus is widespread on the west coast (see map) and occurs from Tain eastwards, but we have no records from Caithness. It surely occurs in the county, so who will be first to find it? 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. An active colony is a spectacular sight, and, despite worries that have been expressed, completely harmless. 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 Caithness - there are many species and little is known about them) please collect a specimen, kill it by freezing, and send it to me. 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 please be sure to report it.
Murdo Macdonald |
