During my visit to the Upper Neath Valley today I found this Cuckoo Bee. Luckily it sat well enough for me to take a few record shots and luckier still they show enough detail to confirm its identity. The key feature in this particular case is the antenna. First of all the antenna of this bee has 13 segments which make it a male (females have 12 segments). The markings of this bee are consistent with Vestal Cuckoo Bee (Bombus vestalis) and Gipsy Cuckoo Bee. The most reliable means of separating the two is by looking at the respective lengths of the 3rd and 5th segments of the antenna. In the Vestal Cuckoo Bee the 3rd segments is much shorter than the 5th segment but the Gipsy Cuckoo Bee shows the 3rd segment near equal length to the 5th, as shown below.
The host species for the Gipsy Cuckoo Bee is the White-tailed Bumblebee (Bombus lucorum).