Highland Diary

Tree Bumblebees and Saxon Wasps, new colonists in the Highlands

Tree bumblebee, Bombus hypnorum

Late one afternoon in early July I wandered out of the house for some exercise. As I made my way up the road I casually observed the insects gathering nectar and pollen from the brambles  growing along the roadside.  I noted several butterfly species along with half a dozen species of bumble and cuckoo bees. My attention was drawn to a very distinctive bumblebee with a bright orange thorax and white tipped black abdomen which I recognised as a Tree bumblebee, a new species to the Highlands. Tree bumblebees have recently extended their range across Europe arriving on the south coast of England in 2001. Since then they have colonised the south and rapidly extended their range northwards through the UK. It’s an early emerging low ground species with a preference for flower rich woodland edge and gardens. The later flowering season of plants in remote highland glens and the Northern and and Western Isles may limit its progress north. The first Highland record was in Easter Ross at the end of June a few days before my sighting. Since then I have seen males and workers foraging in a number of  locations scattered through the western end of the Great Glen. Locally it looks as though Tree Bumblebees  are well established and here to stay.

A few days later I found a rather large social wasp crawling up the window of the back porch. I caught it and potted it up for for a closer inspection. An unfamiliar yellow face adorned with a triangle of small black spots stared back at me. After consulting a few books and a trawl of the internet I tentatively identified it as a Cuckoo wasp, Vespula austriaca, a species that is a nest parasite of other social wasps. The female cuckoo enters a wasps nest, kills the resident queen and takes over the colony. The cuckooed workers unwittingly remain to raise the the usurpers brood . The cuckoo wasps progeny are all either males or females as they do not need to produce a worker cast. The wasp in the pot seemed fairly docile so I got my camera and tripod set up and risked tipping it out on to a fern on the rockery in the garden. It stayed put and obligingly posed for a few id mug shots. A couple of evenings later another unfamiliar face appeared on the rockery. After taking a few mug shots I fairly confidently identified it as a tree wasp. To get id confirmation I sent the images along with those of some of Norwegian wasps that I had previously photographed in the garden to Murdo MacDonald, a wasp and bee guru who runs the Highland Biological Recording Group. He quickly confirmed my identification of all three and was pleased to get the records as the group are just starting to gather records for a Social Wasp Atlas of the Highlands. Three new species for a previously empty hectad immediately upped to four with a record of Common wasps in my garage. A few evenings later I discovered another unfamiliar face peering at me from under a raspberry flower. It was a long-faced Dolichovespula species of wasp either a Norwegian or Saxon wasp. The latter arrived in the UK in the late 1980’s and has been moving north at a slower pace than the Tree Bumblebee. It’s still rare in the Highlands and so far not recorded in Lochaber. Over the next ten days or so social wasps started to receive more attention from my lens. Red wasp was added to my photo collection and I recorded some interesting Common wasp behaviour. I observed workers chewing the heads off creeping thistles in order to feed on the sap oozing from the cut ends. I continued to find and photograph Saxon type wasps. Saxon wasps are closely related to Norwegian wasps and are very difficult to separate in the field. The markings on social wasps can be quite varied making identification difficult. After emailing some images to Murdo I got a reply confirming Saxon wasps had indeed made it north to Lochaber.

What’s next on the long march north? My money would be on the Comma butterfly. In recent years it has colonised northern England and is now well established in central Scotland. The closely related Peacock butterflies came north to the Highlands in a Painted Lady year and stayed on to become resident. Throughout the UK 2019 is proving to be an exceptional ‘Painted Lady year’ for these showy migrants from north Africa. Hopefully there will be fellow travelers following in their wake.