by John Smit, researcher at European Invertebrate Survey – the Netherlands / Naturalis Biodiversity Center, the Netherlands.
This month guest author, John Smit, discusses the conservation of the Sand-coloured carder bee (Bombus veteranus) in the Netherlands, a species which has experienced widespread declines across the country.
Latin name: Bombus veteranus
Common name/s: Sand-coloured Carder bee
Colour pattern: Very constant, all yellowish grey (sandy coloured) with a black thoracic band and thin bands of black hairs on abdominal segments 3-5 in queens and workers and 3-7 in males. Freshly emerged specimen can have bright yellow hairs on the second abdominal segment, especially queens.
Favoured flowers: Red clover, white clover, common comfrey and, to a lesser extent, common bird’s-foot trefoil and water mint. Males can frequently be found on Asteraceae like creeping thistle and goldenrod, but also on sea holly (Apiaceae).
Global region: Entire Palearctic, from western France to the Siberian pacific coast, not present in the Mediterranean part of Europe, nor in England
Geographic distribution: Europe: Austria, Belarus, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Latvia, Lithuania, Luxembourg, the Netherlands, Poland, Romania, Slovak Republic, Sweden, Switzerland, Ukraine. Asia: Russia up to the Pacific coast, including Altai and Sayan mountains and northern Mongolia.
Conservation status: Least Concern
Bombus vetranus is mainly found in the plains of northern Europe, in the southern parts it is confined to slightly higher elevations, with the French Central Massif as the southernmost record. It has disappeared over much of its distribution over the last 100 years, leaving it patchily distributed at present. This is well documented in the Netherlands, where it occurred throughout the country up until the 1970’s, followed by a steep decline. At present it is known from only two areas, along a river and a former estuary.
Evidently, it needs large, open and flower rich areas. The extensive agricultural areas in the Netherlands provided a suitable habitat for this species until agricultural intensification was introduced followed by the use of fertiliser. The borders between the smaller fields and meadows, often consisting of hedgerows, made way for barbed wire and the clover-fields used as a natural fertiliser all but disappeared. There seems to be a strong link between the disuse of red clover as a natural fertiliser and the sharp decline in some of the bumblebee species in the Netherlands. In fact, recent pollen-analyses on Bombus veteranus revealed a strong preference for both red and white clover, as well as common comfrey. Comparison of the pollen load of museum specimens with those of recent specimens revealed a shift in quantity from 64% of both red and white clover together in museum specimens to just 27% in 2017. Conversely common comfrey increased from 24% to 61%, though there are noted differences between the three recent localities surveyed, ranging from 46% at Tiengemeten to 71% at the Biesbosch.
Bombus veteranus is a late appearing species, with queens emerging from hibernation in the end of April or beginning of May and the first workers typically appearing around June, at least in the Netherlands. This is a disadvantage regarding nesting places, compared to the much more common earlier emerging species. It is reported in the literature that nesting typically occurs on the surface, amongst tall grasses or mosses, but can also be underground. The one nest recently found in the Netherlands was situated underground (video below). It consisted of a clump of cells the size of a man’s fist, with no more than 200 to 250 cells. Inside the nest two larvae of the hover fly Volucella bombylans were found, which live as scavengers at the bottom of the nest.
A species action-plan was drawn up for the Netherlands, with measures at the population level. The main goals are to reconnect the two remaining distribution areas and to provide the means for Bombus veteranus to return to the agricultural areas in the Netherlands, where this species can be used as an indicator, or an umbrella species for a more sustainable agricultural system.