The outliers

European hornets are long established in the south of the country and, like many insects, their range is spreading northwards.  The 10 km blue squares on this map from iRecord show all UK records for Vespa crabro this year.  The wiggly blue box delineates our local vice-county, South Northumberland (VC 67).  Note that the rectangular blue symbols in Scotland and Ireland are motorway numbers - they have no hornets.

Our hornets are shown in two blue boxes at the top because data were entered by two people (the other being the vice-county recorder for moths) at points 50 m apart in the reserve and, by chance, the two points are in different 1 km squares which are in different 10 km squares!  Hence two blue boxes.

As you can see from the first map, our hornets are way outside the previous recorded range (90 km from the nearest data point in Yorkshire).  When I entered the record of our local hornets, with a photo, I got this response, although the record has since been accepted.

It is intriguing to consider where the hornets came from.  It is possible that they have been around for a while and no-one noticed although that seems unlikely as they are pretty obvious, being large, yellow and noisy.  iRecord data go back 10 years and contain only one other record for the county, 40 km farther north in Harwood Forest in 2015.  That record has no supporting photo and from the details provided it seems unlikely to be correct.

A second possibility is that the foundress queen for "our" nest flew the 90 km from Yorkshire, possibly wind-assisted.  I don't know how far European hornet queens are prepared to fly but I have read that Asian hornet queens (Vespa velutina) in France can spread at up to 60 km a year.

The third possibility is that the queen that founded our local colony hitched a lift during hibernation.  There is a large bakery and food factory just across the road which presumably imports a lot of material on pallets, etc.  We know that the Asian hornet arrived in France from China in a consignment of pottery in 2003 or 2004 so maybe our European hornet hitchhiked from the south in a similar way.

If these hornets are true outliers there is some concern about how they might fare in subsequent years.  Depending on how the queen of this colony was mated (and most queens mate only once) there is a fairly high chance that most or all of her offspring are full siblings. This means that matings of the males and new queens raise the prospect of inbreeding weakening later generations. Male hornets, like all other male wasps and bees, are haploid, that is they have a single set of chromosomes.  All females (workers and queens) are diploid, with a double set.  If my calculations are correct, theoretically sibling mating will lead to 25% of the next generation having two identical copies of the sex-determination gene so rather than being female workers they become diploid males, meaning that they are a drain on resources, and thus weaken the colony without contributing to the genetic line or the workforce.  The proportion of diploid males increases to 33% in each of the following two generations (the maths is quite complicated so I haven't gone any further than that).  In theory this would be bad news but the European population of Asian hornets is all thought to have come from a single foundress queen and it doesn't seem to have done them much harm, even though they do produce quite a lot of diploid males.