6
Essex Bumblebees - A Call for Help!
There has recently been some national publicity about the serious decline in populations
of many of our Bumblebee species. Currently five species are on the National
Biodiversity Action Plan lists. I have been recording the Bumblebee species in Essex for
about fifteeen years, and the local situation seems in line with national trends. It is
assumed that Bumblebees, most of which depend on large tracts of flower-rich habitat,
have been hit hard by agricultural intensification in recent decades. There is no doubt that
parks and suburban gardens have become increasingly important as foraging-sites for the
commoner species, but it needs to be established whether they provide suitable habitat for
the whole life-cycle, and for which species.
Reports sent in from all parts of the county, and my own observations are now building
up to a reasonably comprehensive picture of the status and distribution of the Essex
species. We can compare this with the national atlas prepared by the Institute of
Terrestrial Ecology, published in 1980. According to that, twelve species of the genus
Bombus were present in the county between 1960 and 1980, together with five species of
the closely related genus Psithyrus ('cuckoo bees', now included within the genus
Bombus). One difficulty with making comparisons with the present situation is that we do
not know how thorough the earlier survey was, and much valuable information about
exact localities appears to have been lost. However, with that qualification in mind, there
are some things which can be said. There are six species of Bombus which remain very
widespread in the county. They have been recorded in nearly every 10km. square, and
probably occur in all of them. These are Bombus terrestris, pratorum, lucorum,
pascuorum, lapidarius and hortorum. However, though they are still widespread it would
be wrong to be complacent about these species. Loss of habitat has occurred on such a
massive scale it seems likely that populations are far smaller than previously. Of the six,
B. hortorum seems to be the least common, though this may be misleading. Each nest has
smaller numbers of workers than other species, and the flight period seems to be
somewhat shorter, resulting in its being recorded less frequently.
The remaining six Bombus species appear to have always been more localised in Essex
(and elsewhere). Bombus ruderarius is possibly under-recorded because of its similar
appearance to B. lapidarius. Previously recorded in twenty five 10km. squares across the
county, its current distribution appears to be more restricted to the East and North East.
Any records of this species, but especially from the West and South of Essex would be
recieved with interest. Two other localised species are B. humilis and B. muscorum.
These are similar in appeaiance to B. pascuorum. Both species occur in what is left of our
estuarine and coastal grazing marshes, but there are a few interesting inland records.
Though probably much less common than before, muscorum is hanging on in small
numbers with roughly similar distribution in East and South Essex. By contrast, humilis
seems to be holding its own along parts of the Thames Estuary, but seems to have
disappeared altogether from North East Essex. Bombus ruderatus was probably always
very localised in Essex, but now seems to be extinct or on the verge of it. I have only
three records since 1980. These sightings were near Great Chesterford, the Dunmow
railway cutting, and near Braintree. Subsequent visits have failed to confirm the
continued presence of the species. One possibility yet to be explored is that this species
now inhabits suburban gardens, like the similar but smaller B. hortorum. Again, close
observation of such gardens, especially in the areas mentioned would be worthwhile, and
I'd be very interested to hear of possible sightings. I had given up hope of finding the
remaining two Bombus species when Peter Harvey found one of them - B. sylvarum - in
South Essex. This species is now the subject of both national and county Biodiversity
Action Plans, but at least one of its Essex sites is about to be destroyed by 'development'.
The other - B. subterraneus - now appears to be extinct in Essex.
Essex Field Club Newsletter No. 25, May 1998