Cornwall has nationally important populations of rare bumblebees (Bombus), particularly the BAP priority Bombus humilis and B. muscorum. It also has historical records of four nationally notable species and three rare species presumed extant. The records in the ERCCIS/BWARS (Bees, Wasps and Ants Recording Scheme) data in comparison with accounts by Almond (1975) and Saunders (2003) indicate a startling decline in species.
The decline of bumblebees undoubtedly stems from agricultural intensification (Benton, 2006) simply through reduction of flower rich foraging habitats. The bumblebee’s declines have been acute because of their need for large areas of suitable foraging habitat, this may extend to 1km2 of flower rich grassland for one nest of a rare species (Edwards and Williams, 2004). So to sustain a viable population (i.e. many nests) a flower rich landscape is needed rather than just a field or site (in this context flower rich refers to a more literal description of habitats with lots of flowers in flower and sometimes may be applied to improved clover leys as much as unimproved more “natural” grassland). For many of the rarer species large areas of flowering Fabaceae for pollen are also important (Goulson et al., 2004).
Climate is another factor to affect Bombus decline. Species at the edge of their climatic niche in Britain (B. distinguendus and B. sylvarum) are more vulnerable to the effects of habitat loss (Williams et al., 2007).
The whole north coast of Cornwall represents one such bumblebee reserve by consisting of a long strip of relatively unbroken flower-rich grass and heath. Other important areas are The Lizard; the mid-Cornwall moors and (much less than formerly) Bodmin Moor.
It is hoped that new agri-environment schemes such as pollen and nectar margins could be targeted to benefit Cornish bumblebees. Large landscape scale projects for the Chough Pyrrhocorax pyrrhocorax and Large Blue Maculinea arion are likely to benefit rare bees, as are large conservation grazing schemes such as on Bodmin Moor (if large summer flowering areas are planned and created within such schemes).
Bumblebees are an interesting and rewarding group to record. It might be thought with only 22 species they are an easy group, but they are not. Some visual characters get worn and can be unreliable resulting in misidentification; B. muscorum and B. humilis are frequently almost impossible to separate in the field. Consult Bumblebees (Benton, 2006) for keys.
This account builds on the previous work by B.E. Jackson (Jackson, B.E., 1997. Bumblebees in Spalding (Ed.), Red Data Book for Cornwall and the Isles of Scilly.). National distributions are taken from Bumblebees (Benton, 2006). Local distributions are based on the records held in the ERCCIS/BWARS database, Saunders (2003), Almond (1975), and G.M. Spooner field diaries 1981-85 (held at the Natural History Museum). National classifications are based on Jackson (1997) and UK BAP plan revised species list (Anon, 2007).
1. Nationally notable bumblebees
Bombus ruderatus Large Garden Bumblebee
Bombus distinguendus Great Yellow Bumblebee
Bombus rupestris Large Garden Bumblebee
Bombus sylvarum Shrill Carder Bumblebee
Bombus subterraneus Short-haired Bumblebee2. Locally scarce bumblebees
Bombus muscorum Moss Carder Bumblebee
Bombus soroeensis Broken-belted Bumblebee
Bombus humilis Brown-banded Carder Bumblebee
Bombus ruderarius Small Red-tailed Bumblebee
Bombus jonellus Short Heath Bumblebee
Bombus monticola Mountain Bumblebee