Eyes on the bramble

The bramble is alive with insects at the moment, its flowers the lure that attracts flies, beetles and a multitude of bees. Although many of the visiting insects are familiar enough it is always worth spending some time at a flowering bramble to see what else might be attracted in. Over the years, for example, bramble has provided me with some of my best views of white admiral and black hairstreak butterflies, not to mention several interesting species of beetle.

Today though, it is the commonplace insects that are my focus, the bramble providing an opportunity to brush up on my bumblebee identification and to try out a new identification ‘app’ developed for the ipad by TouchPress . The most common bumblebee on this particular patch of bramble is the tree bumblebee Bombus hypnorum, a recent colonist whose populations here in the Brecks appear to be going from strength to strength. This attractive bee was first recorded in Britain back in 2001 but was not recorded from Norfolk until 2008, when an individual was found in Earlham Cemetery. Being one of the easier bumblebees to identify, with (in queens, workers and most males) a ginger thorax, black abdomen and white ‘tail’, you stand a good chance of spotting one this summer here in Norfolk. Tree bumblebees, as the name suggest, usually nest above the ground in holes in trees or buildings. They have also taken to using nest boxes of the type erected for hole-nesting birds like blue or great tit.

The arrival of the tree bumblebee is perhaps unsurprising given that its distribution elsewhere in Europe sees it established as far north as the Arctic Circle. The colonies of this species can be sizeable with perhaps as many as 200 workers supporting them, which might explain the numbers that I am seeing here on the bramble where they outnumber the white-tailed and buff-tailed bumblebees flying alongside them. Some of the other bees present will need more careful scrutiny, however, if I am to pick out some of the cuckoo bumblebees that might be present. Cuckoo queens take over the nests of true bumblebees, ousting the resident queens to secure the labour of their workers, which then help to raise cuckoo males and females.

New Bumblebee puts in an appearance

The bumblebees are one of those groups that I have never entirely got to grips with. Given their appearance, with their bands of colour, you might expect them to be rather easy to identify. This, however, is not the case, as some species pairs can look surprisingly similar. This is compounded by the fact that some of the species have different colour forms and all of the species tend to be on the move for most of the time. The key to identifying bumblebees is to invest in a handnet and a large plastic tube in which the bee can be place so you can look at it with a hand lens. I push a small tissue into the pot, gently confining the bee to the end of the tube where I can then see all of the key features.

The other important thing when it comes to identifying bumblebees is to determine the sex and caste of the individual you are looking at; is it a queen, a male or a worker (the latter being absent in the so-called Cuckoo bumblebees)? Telling males from females takes a bit of practice. Although not entirely reliable, male bumblebees usually have some pale hairs on the face, while those of the female are usually black. More reliable, however, are differences in the antennae; females have longer antennae, made up of 13 segments, while the shorter antennae of the males have twelve. A final thing to look at is the shape of the tip of the abdomen. In males this is rather blunt and round, containing the reproductive apparatus, while in females it contains the sting and is more pointed.

The different bumblebees can be grouped according to some basic colour patterns, the colour and positioning of which are the key feature to examine. However, the resulting groupings often contain more than one species (often a single common one and several rarer species) and then you have to look at other features. One of the easiest species to identify, at least in my experience, is the Tree Bumblebee. This species sports a ginger-brown unbanded thorax, a mainly black abdomen and a white tail. Judging by the number I see foraging on the plants at work, I reckon we have one or more healthy colonies nearby and I occasionally get them in the garden at home as well.

The Tree Bumblebee is a very recent colonist, first recorded in the UK in 2001 when an individual was found in Wiltshire. Since then it has spread across much of southern England, where it often nests above ground, sometimes favouring nest boxes erected for birds. Daughter queens are on the wing at the moment so do keep a look out for them.