04 September 2013

Good for bees, bad for bees

There were Shrill Carder Bees (Bombus sylvarum) near the Kenfig River, today, where Barry Stewart recently discovered an encouragingly healthy population of this threatened species. At least 4 individuals were found including one on Red Bartsia (Odontites vernus), briefly, before having a quick go on a Bramble (Rubus agg.), then Hoary Mustard (hirschfeldia incana) and away. However, at a decent stand of Himalayan Balsam (Impatiens grandulifera) three were found nectaring alongside a number of other Bumble Bee species; none of which seemed to be in any rush to leave the banquet. At this time of year Himalayan Balsam, a much maligned invasive species, clearly provides an important source of food and may even be a major benefit to threatened bee species? Some of the more traditional sources of nectar to the Shrill Carder Bee were less obvious today such as Creeping Thistle (Crisium arvense) and Red Bartsia, however, Himalayan Balsam was in profusion. I imagine that this rich source of food will be important to 2nd generation queens that must survive the winter to continue the population again next year?

Last weekend, at Brunel Dock, this rather striking Conopid Fly had me stumped for a while. Appearing to me to be half hoverfly and half potter wasp; I was wondering whether I had stumbled across something new to science! The halteres finally caught my attention and directed me away from wasps, to flies and eventually, with the aid of Chinery (and the internet), to Physocephala rufipes. The larvae of this stunning fly parasitise bumble bees and occasionally social wasps. Thanks to David Clements for confirming the identification and adding that it's a male.


Barry Stewart said...

Nice pics Mark, you did well to find one using the balsam that was not covered in pollen. The vast majority I saw at this site last week were on Red Bartsia, so interesting they seem to going for other species. We've renamed the bartsia 'sylvarum crack' as they seem totally addicted to it, but perhaps they're now switching to something harder?

Paul Larkin said...

Here in Kent bramble is important for sylvarum earlier I the year as is meadow vetchling. The main forage at present is black horehound and to a much lesser exent birds foot trefoil. Having surveyed my local area in North Kent over the last few years it is quite apparent that the population of sylvarum and humilis is quite widespread if local.