I'm still thinking about spring and here is some information about the White-tailed bumblebee, Bombus lucorum.
This large queen bumblebee is seen from March onwards usually, seeking nectar to build her resources to start a new nest and begin to lay eggs.
As with all bumblebee species, she will have mated the previous year and is already fertile. She will lay eggs that develop into females or workers initially, and they are produced from fertilized eggs. Male bumblebees are produced later in the year and are formed from an unfertilized egg (Goulson, 2010).
Here, the explanation gets quite complex. Females are diploid, with two copies of each chromasome and produce eggs by meiosis (as humans do). Males are haploid in which each gamete has just one copy and they do not require sperm to be produced.
Identification of White-tailed bumblebee queens is reasonably straight forward. They have two lemon yellow coloured bands and a white tail. The queen will be large, and a similar size to the Buff-tailed bumblebee.
White-tailed bumblebee queens. Top left Copyright: Ian Collins
It is possible to distinguish the Buff-tailed and White-tailed queens apart by looking at the yellow band colour and the tail colour, (buff coloured and white respectively). As previously written, Buff-tailed bumblebee queens have a 'dirtier' yellow banding.
It begins to get a bit more tricky once the female workers are about, and they are more difficult to separate. The tail colour in female workers may be white in both species and it is for this reason that when recording them, it is easier to note them all as Bombus lucorum agg. which is short for aggregate.
Above is a map of the distribution of White-tailed bumblebee in Radnorshire and Breconshire, courtesy of the Biodiversity Information Service.
There are a few white-tailed species of bumblebee in the UK, with two yellow bands. These include species that are less commonly recognised; Bombus cryptarum and Bombus magnus which are more of an upland species and more western in their distribution. The easiest way to separate them would be by using DNA analysis.
Another white-tailed species with two yellow bands is Bombus soreensis, which tends to be a little smaller on average than Bombus lucorum. It can be reliably separated from Bombus lucorum by examining grooves on the mandibles in female bees and genitalia in males (BWARS, 2020). Again, another reason for recording two banded, white tails as Bombus lucorum agg.