Because velutina is constrained by its biology. Velutina needs high density insect populations to sustain it (so it needs wetlands) which we don't have by and large in the UK and because it needs nesting habitat which requires the wetlands to be forested or be in close proximity to forests. Velutina is largely concentrated around the Bordeaux area and that's no accident. It is struggling to break out from there.
Something else to consider. The vast majority of queens die naturally in temperate climates. I don't fully understand the reproductive populations for velutina but because it's a mass species I suspect it's similar to vulgaris and germanica and releases circa 1000 queens per nest (don't quote me on this as this is speculation). In temperate climes only 1 or 2 queens will survive. Add the channel and the timing for translocation to be successful and the probability of velutina crossing the channel and establishing itself is remote. If it were to happen then I would suspect an act of intentional bioterrorism!
Something else to consider. The vast majority of queens die naturally in temperate climates. I don't fully understand the reproductive populations for velutina but because it's a mass species I suspect it's similar to vulgaris and germanica and releases circa 1000 queens per nest (don't quote me on this as this is speculation). In temperate climes only 1 or 2 queens will survive. Add the channel and the timing for translocation to be successful and the probability of velutina crossing the channel and establishing itself is remote. If it were to happen then I would suspect an act of intentional bioterrorism!
