Flight season: May into September.
Flowers visited: Dandelions, ox-eye daisy, oil seed rape. Males and new queens like thistles, brambles, teasels, ragworts, and lots of garden plants like lavender.
Nesting preferences: A parasite of the red-tailed cuckoo bee, Bombus lapidarius.
Status: Formerly scarce with a mostly southern distribution, this bee has seen a large range increase (potentially to do with climate change) but is still fairly scarce North of the midlands and is unrecorded from Scotland.
Similar species: Superficially similar to the red tailed bumblebee, Bombus lapidarius, females can be easily separated by their very dark wings and lack of a pollen basket (hind tibiae is hairy instead of shiny). Males are more difficult but easily separated from B. lapidarius (if you know it’s a male: 13 antennal segments instead of 12 in females) as they don’t have the bright yellow markings. However, they are similar to the rare red-shanked carder bee, Bombus ruderarius, and can only reliably be separated by looking at their genitalia, but this bee is not found in the valley.
Description: An extremely large bee, the females especially are built like tanks. The soft velvet back fur meeting striking red on her tail. Her wings are a beautiful iridescent purple black, shimmering in any light. Males are a bit smaller and without such amazing wings but are decidedly variable: becoming extremely pale in some cases. Males can be seen forming excitable lekking swarms on sunlit hillsides, all keen to find a wife. This behaviour possibly relates to their common name, the hill cuckoo bee, Bombus rupestris.
Where to see them: I have only ever seen this species once in the valley and that was in my garden in Bronygarth! This is quite close to the Northern reaches of its range and so it is not likely to be encountered often. However, as the red tailed bumblebee (Bombus lapidarius) is very common in the valley, there is potential to find this be in most locations.
Hill cuckoo bee Bombus rupestris
A comparison between a queen red-tailed bumblebee (Bombus lapidarius) (L) and the hill cuckoo bee (Bombus rupestris).