species found in Somerset

(identification problems, with the colours fading out with age and wear)

A problem group: Bumblebees appear to be easy to identify, or at least the commoner species, as books and charts show them with clearly defined coloured bands or other easily distinguished features. Sadly, this may not be the case as some insects may have had the hairs of the bands worn away, others have lost most of the colour in the bands while some may have missing or even extra bands. This is not to put people off studying these fascinating creatures, rather to warn that what you see may not be what you think. In other words, identification may require far more than a cursory glance. Digital photography has brought the possibility of helping this identification by taking multiple pictures from differing angles and examining the appropriate features in detail, but the final arbiter of any difficult case must remain studying a specimen under a stereo microscope. Males are the best choice if this is required, as they only have one function, while there is always a surplus available.

Somerset: Each part of Britain has its own regulars and specialities, so this section refers only to those species presently found in the ancient county of Somerset with all its varied landscape and gardens. This encompasses farmland, rolling hills, the wild expanse of Exmoor, the great wetlands of the Somerset Levels and Moors, the Quantock Hills and Mendip rising starkly up from near sea-level to over 1,000 feet.

Cuckoos & true bumblebees: This sub-family is divided into two distinct groups; 'true' bumblebees, which are social, and 'cuckoo' bumblebees, which depend on the first group, without forming a social group of their own.

True bumblebee colonies start each year with the emergence of an over-wintering queen from her underground resting place. She had been fertilised the previous year and lays her fist eggs in spring and rears these, feeding and tending them herself. This first brood is made up of workers which then take over the duties of the queen, leaving her to concentrate on egg-laying. The eggs are laid in wax cells containing honey made from nectar, very similar to those made by honeybees. Later in the year, males are produced alongside the workers and eventually young queens who will over-winter to form the next generation. Bumblebee nests may be on the surface or underground, depending on the species, and vary from a dozen or so inhabitants to hundreds.

The second group contains the cuckoo bumblebees, which do not make a nest of their own but take over those of another species and persuade the other workers to rear their young, as if they were their own. This done by a female cuckoo bumblebee forcing her way into the normal nest and either killing the existing queen or simply ignoring and sidelining her. Whichever occurs, she lays her eggs and these are reared by the true bumblebee workers. Those likely to be found in many gardens, are Bombus campestris, B. sylvestris and B. vestalis; while B. barbutellus, B. bohemicus and B. rupestris are distinctly less common.

Relative abundance: Gardens are possibly the most important of all these habitats, being responsible for helping maintain the seven common species so vital in pollinating trees, flowers and crops. These 'true' bumblebees, Bombus hortorum, B. lapidarius, B. lucorum, B. pascuorum, B. pratorum, and B. terrestris have been recently joined by another, B. hypnorum, which has spread into England from the Continent in recent years, and is common in many gardens. Much more local are B. jonellus, B. monticola, and B. muscorum; while B. humilis, B. ruderarius, B. ruderatus, B. soroeensis and B. sylvarum are distinctly rare in this county.

These latter species are generally found out in the open countryside and have suffered as the long period of wild flowering has been reduced by changes in agriculture. Recent research has shown that in the case of Bombus sylvarum the species needs continuity of flowering from the time of the start of the colony at the end of April to October, when it dies out. Furthermore, calculations indicate that it needs 100 sq. kilometres to provide a viable area for colonies to flourish. Only large wild areas, such as are found round Shapwick Heath and adjoining reserves, are able to supply this nowadays; hence the reason for previously-common species reducing so far or dieing out completely. Modern farming, whether grassland or arable, does not allow the continuity of flowering needed to maintain their colonies. However, the recent introduction of subsidies encouraging the planting of a wild flower strip round fields has shown promise in encouraging the less common species.

Pollination: Why is all this important? Bumblebees are amongst the most vital pollinators of garden and wildflowers, as well as fruit trees, and our food depends on this taking place successfully. A great deal of research is going on into what to do about the continuing reduction in insect pollinators, while colonies of bumblebees have long been used to pollinate crops such as tomatoes in greenhouses. Let’s hope that the experts can come up with affordable ways of dealing with the problem. In the meantime, the more we can learn about this fascinating group, the better.

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