Wandering wool-carder?

One of Britain's most spectacular bees (in my opinion at least) is not a bumblebee, but the wool-carder bee Anthidium manicatum, one of the Megachilinae which includes the leaf-cutters. So, when I saw one basking on a Geranium leaf during a welcome burst of sunshine a few days ago (it then moved onto common bird's-foot trefoil Lotus corniculatus), I had to take a photo - however, when I looked more closely, it was almost, but not quite, as I expected.

The wool-carder bee Anthidium manicatum

At first glance, it looks much like any other individual of this species, however the yellow markings are far more strongly developed than is usual for a British specimen - they are usually spots to the sides of the abdomen with some in the midline and partially joined to form weak bands on the rear segments as shown in many books including Baldock (2008). A clearly striped individual like this is more like a continental European specimen - indeed, an experienced hymenopterist from BWARS remarked that he had never seen an individual like this in Britain. So, is this just an aberrant specimen, or - and I shall speculate a little - might something else be happening?

In Britain, A. manicatum is only locally common in the south, especially SE England, and becomes scarcer as you look further north. Until 1993 it was scarce even in the SE, after which it began to expand its range (Edwards, 1997) and become common is some southern locations. This suggests that temperature is a key factor in its distribution and to me indicates that this is one of many invertebrate species expanding it range as a result of climate change. Its common name of 'wool-carder' referes to its habit of shaving the hairs from downy plant leaves (such as Stachys) in order to line its nest - possibly a behavioural adaptation to provide insulation due to a requirement for high temperatures.

Considering the colour pattern, this specimen (like those in continental Europe) clearly seem to display wasp-mimicry, while typical British specimens do not, or at least only weakly. This would be a clear defensive adaptation, so why do British specimens tend not to show it? One possibility is that the relatively dark colouration permits more rapid warming when basking  - certainly this individual was also vibrating its wings at intervals, a typical insect behaviour used to warm the flight muscles. If, further south in Europe, this aid to warming is outweighed by the benefits from defensive mimicry, then the clearer stripes might be an advantage. This leads me to consider three possibilities:

1. This is an aberrant individual with no further significance.
2. It is a vagrant continental individual.
3. It is a British individual and increased temperatures are selecting for stronger stripes.

Of these, #3 is the most interesting but also the most speculative and there is no way of knowing from a single sighting. However, I intend to watch closely - males are highly territorial (and may kill other bees) so might use the garden regularly - and would be interested to hear from anyone else who has seen a specimen like this in Britain.

Anthidium manicatum basking on common bird's-foot trefoil Lotus corniculatus

References

Baldock, D.W. (2008). Bees of Surrey. Surrey Wildlife Trust, Woking.
Edwards, R. (ed.) (1997). Provisional Atlas of the Aculeate Hymenoptera of Britain and Ireland. Part 1. BWARS/BRC, Huntingdon.