Laurustinus blossom and Tree Bumblebee

The blossom of Laurustinus, Viburnum tinus, is brightening the gardens around town. This morning I surprised this Tree Bumblebee queen, the first of the year, basking on the sunny flowers.

A beesy beesy day

We've had a lovely, mild, quite sunny day today. Bees came out of their various hiding places and gorged on the garden flowers. Top bee magnets were the hardy geraniums and the hedge woundwort. At least one old Osmia rufa was still about, very late for this spring species. The first Anthophora furcata of the year turned up, at the usual time of the year. She fed on Hedge Woundwort (above, note how thick the bright red tail looks) and Iris. A male was also about.

Bombus pascuorum entering Iris.

 The only B. lapidarius I saw today

Osmia caerulescens female sunbathing

Competition for the hardy geranium, Bombus hypnorum and Osmia rufa

Osmia rufa leaving hardy geranium, note the visible 'horns'

Megachile centuncularis on Bird's foot trefoil

 Bee list

1. B. hypnorum hardy geraniums, cotoneaster. Males and Queens about.
2. B. pascuorum foxglove, purple toadflax, hedge woundwort.
3. B. hortorum foxglove, hedge woundwort, lamium maculatum
4. B. terrestris, Stachys byzantina, trying to feed on Lamium maculatum
5. B. lapidarius poppy, just one.
6. B. pratorum hardy geraniums, cotoneaster
7. Megachile willughbiella male on thyme, stachys
8. M. centuncularis birds foot trefoil, hardy geraniums
9. Anthophora furcata male patrolling, 1st female of yr., Teucrium, Iris, Hedge woundwort, Herb robert.
10. Osmia rufa, hardy geranium
11. O. caerulescens, sunbathing
12. Honeybee Philadelphus

Tree bumblebees mating

For the last few weeks, Tree bumblebee males have been travelling full speed around the garden marking leaves and stems with pheromones to attract queens. The males and new queens have been produced by bumblebee nests as they are reaching the end of their life cycle. Males leave their natal nest and then hang around the entrance of nests possibly hoping for a queen to emerge. Workers are most likely found dead than alive once the males and queens fly from the nest as their role is completed.
I watched a Tree bumblebee nest in my local wildlife garden, as common in this species, they chose high places, and nest boxes and under eaves are the most easily spotted nest sites. A cloud of males hovered around the entrance.

 Today I found the mating pair above on hogweed, the first I find for this species. It is hard to believe that the Tree Bumblebee was not found in N England 10 years ago, now it is so common and widespread. Here is the distribution map for this species from BWARS B. hypnorum project.
More info on B. hypnorum in BugBlog here.

Watching bees on foxgloves

June is peak Foxglove, Digitalis purpurea, season. This year, we have quite a few in the garden, and luckily one of them faces the conservatory, which allows me to observe visiting bees quite closely. Today I watched the bees feeding on it in sunny spells between showers. Foxgloves are said to be adapted to be pollinated by bumblebees: they have large, bell shaped flowers with a large landing lip and hairs that might deter smaller bees or other insects from entering. Indeed, bumblebees, and particularly long-tongue species, can reach the nectar deep inside the flower and actually pollinated it are the main visitors. A study in N Yorkshire found that Bombus hortorum (top, individual leaving flower with pollen load, and another individual just visible inside a lower flower) was the main visitor and preferred this flowers when available, but another study in Belgium found that B. pascuorum was the main visitor. The tree bee Bombus hypnorum is also a regular. All three species are commonly found on floxgloves flowers in my garden, with B. hortorum being the most common visitor. But other bumblebees, including those with short tongues do often collect pollen by 'buzzing' inside the flower even if they cannot reach the nectar.
 A few solitary bees also visit foxgloves. In my garden the forked tailed flower bee Anthophora furcata regularly visits them, and more rarely the carder bee Anthidium manicatum.
As relatively few species feed on this species, it is a good starting plant to familiarise yourself with bumblebees.
Today, I watched four bee species visiting this particular foxglove stem.

A male A. furcata (above) jumped on each visiting bumblebee to check them out, but was obviously feeding also on nectar. I haven't seen females around yet. The male has similar size and colour than a honeybee, but it has a bright yellow face and a visibly long tongue.

Bombus hortorum is the bumblebee with the longest tongue in the UK (above, with tongue extended). It can also be recognised by its double yellow band formed by the rear of the thorax and the front of the abdomen, and its white tail.

B. pascuorum is the most common all-brown bumblebee in gardens. 

Bombus hypnorum is a very distinctive bumblebee, three coloured: brown/black/white.

The stout black abdomen with lateral yellow patches of the Wood Carden Bee Anthidium manicatum which visited on 1/07/2011.

 Foxglove flowers open from the bottom of the stem towards the top. The plant reproductive parts are located on the roof of the flower, four stamens and a pistil in the middle, so that the body of a bumblebee entering the flower rubs against them. To reduce self-pollination, the flower anthers open first, delivering a pollen load onto bumblebees feeding. Five days later, when the pollen is likely to be exhausted the pistil becomes receptive, increasing the chances that it will be pollinated by the pollen of a different plant. I cut three flowers of a white foxglove in the garden and removed the roof of the flower to expose the reproductive organs. The one on the left, from the top of the flower spike just opened. The lobed yellowish sacs are the closed anthers, and the spike in the middle is the pistil, also closed and attached to the flower roof. The middle flower has open anthers and the pistil, although closed, has started to detach. On the left is the oldest flower from the bottom of the flower spike. Its anthers are almost devoid of pollen and the pistil is now pointing down, so that is easily rubbed by the bumblebee's back and then ready to be fertilised.

A bumblebee view of a foxglove. Note the open pistils on the lower, older flowers.

More information

Arthur A. D. Broadbent and Andrew F. G. Bourke (2012). The bumblebee Bombus hortorum is the main pollinating visitor to Digitalis purpurea (Common Foxglove) in a UK population. Journal of Pollination Ecology, 8 (7), 48-51.

Verboven, H., Brys, R., and Hermy, M. (2012). Sex in the city: Reproductive success of Digitalis purpurea in a gradient from urban to rural sites Landscape and Urban Planning, 106 (2), 158-164 DOI: 10.1016/j.landurbplan.2012.02.015

On the odd life cycle of bumblebees

I stopped by the comfrey patch this morning. The comfrey has now been in blossom for a good month. A Small White butterfly was feeding on comfrey, but I couldn't snap her. A ginger queen Bombus pascuorum fed on the blossom. A queen wasp got comfortable on a leaf and basked in the sun, as did some hoverflies. While I watched a couple of Anthophora plumipes males patrolling and feeding, a tiny worker of the tree bumblebee Bombus hypnorum, the first of the year, turned up (above). As I compared the sizes of these two bees – the bumblebee worker was smaller than A. plumipes - I reflected on the different life cycles of these two bee species. A. plumipes, a solitary bee, has males and females, while bumblebees, in addition of males and females (queens), have a worker caste. In bumblebees there are no males for most of the year: A male has a relatively short - if hectic - life. Upon emergence in the summer, he will find a queen and mate with her. The queen will store his sperm and use it to fertilise her eggs the following spring, when she will emerge from overwintering, build a nest and lay fertilised eggs, which will hatch into worker larvae. She will be busy collecting nectar and pollen from early flowering trees and plants to rear these larvae, and once the workers emerge, they will take over from the queen in collecting more nectar and pollen for subsequent eggs, although they won't reproduce themselves.  In the summer, the last batch of eggs of the queen will produce new queens and males, which the workers will help rear. Once they leave the nest, the founder queen and workers will die and the cycle starts again. Wasps, ants, bees, and bumblebees (hymenopterans) share a weird way to determine the sex of the offspring: fertilised eggs become females and unfertilised eggs become males: a system called haplodiploidy.

  Most sexual organisms have two sets of chromosomes: a set they inherit from their mother and another that comes from their father, but as bumblebees and other hymenopterans do not have a dad they just have a single set of chromosomes, the set coming from their mother.

How strange is that? If you think about it, the system means that bumblebee males don’t have dads, they also cannot have sons, only daughters, although they can have grandsons and have granddads. In addition, this arrangement causes strange relationships between the family members. We are equally related to our parents than to our kids – on average – but due to haplodiploidy, bumblebee sisters are more strongly related than they are to their mums. This is because full sisters have received an identical set of chromosomes from their dad, in addition to the set they receive from their mum, which is a mixture from the sets the queen received from her parents.

 This unbalanced genetic relationship between mother-daughters and sisters is thought to underlay the evolution of the worker caste, which do not reproduce, but help their mother to rear their own sisters.

The solitary bee Anthophora plumipes

A wasp? No, the exquisite wasp mimic hoverfly Myothropa florea

This is the real wasp. A queen common wasp 

Hoverfly Syrphus ribesii 

Another basking fly

A queen Bombus pascuorum

Queens, harlequins and admirals

The last mild, sunny days of autumn are bringing out scores of insects. Standing under a large flowering ivy today the sound of buzzing bees, bluebottles, droneflies and wasps was extraordinary, especially given that November is only a couple of days away. Yesterday, six red admirals sunnied and gorged themselves on the ivy blossom. They are charging batteries before their migration to South Europe and North Africa.

Red Admiral and passing droneflies on ivy

 A green shieldbug, Palomena prasina, climbing a tree.

 Today, a queen Bombus hypnorum fed on lavender flowers. 

 A female Araneus diadematus spider sat proudly on her silky egg cocoon. 

Honeybees on ivy flowers

Dozens of harlequins and 7 spot ladybirds flew about landing on a sunny wall and leaving again.

A tree bumblebee queen

 This tree bumblebee, Bombus hypnorum, queen has been visiting the garden in the last couple of days, with her fresh, striking tawny/black/white pattern very apparent. The last time I saw this species this year was in July, when males patrolled in the garden and queen bees could be seen searching for nest (or hibernation sites). August, three years in a row, yielded no sightings. Yesterday's queen visited Erysimum "Bowles's Mauve". This perennial wallflower, which often appears in BugBlog shots, and I highly recommend in any wildlife garden, has a very long flowering season and attracts a range of solitary bees and bumblebees, hoverflies and butterflies.

This graph shows the number of days per month I've seen this bumblebee in the last three years. Workers are active during May and June, most of the July activity is males marking and patrolling their flight paths and queens. The rest of the sightings in the autumn and early spring are queens feeding or nest searching.

Racing male tree bumblebees

In the last two weeks, the garden has been overtaken by frenzied male bumblebees. They follow a set circuit, round and round, racing from bush to bush and then having a little bumble in each. If you wait for a bit on a particular spot on the route, you are likely to see another bumblebee a few minutes later passing by in the same direction, doing exactly the same. Most of the males I have been able to identify doing this are Bombus hypnorum. Today, a male B. hypnorum - which can be distinguished from the female by his white moustache - got trapped inside the conservatory and I had his portrait taken (above). Many male bumblebees have recently emerged from their nests, never to return, and their mission is to find queens and mate with as many as possible. In many bumblebee species, males' strategy consists on tracing a route, sometimes hundreds of meters long, often circular, depending on the species, and marking certain places along the route with pheromones produced by scent glands in their jaws. Males join already set routes and therefore many males, some of them probably their siblings, go round the same routes every day, stopping to feed occasionally. Queens encountering a route are attracted by the pheromone and are then intercepted by males. The discovery and first description of these male bumblebee flight paths - from Bombus hortorum males - dates back to Charles Darwin, from observations he carried out at Down House. Although he didn't realise pheromones were involved, he noticed bumblebee routes and them stopping and bumbling at places he called "buzzing places", and marveled at the fact that the same or very similar routes were used year after year:

I then followed their route for about a hundred and fifty yards until they came to a tall ash, and all along this line they buzzed at various fixed spots. At the far end, near a pollard oak, the track divided into two as shown in the plan. On some days all the bees flew in the direction I have described, but on others some arrived from the opposite direction. From observations made on favourable days, I think that the majority of individuals must fly in a wide circle. They stop every now and then to suck at flowers. I confirmed that whilst in flight they move at about ten miles an hour, but they lose a considerable amount of time at the buzzing places. The routes remain the same for a considerable time, and the buzzing places are fixed within an inch. I was able to prove this by stationing five or six of my children each close to a buzzing place, and telling the one farthest away to shout out " here is a bee " as soon as one was buzzing around. The others followed this up, so that the same cry of " here is a bee " was passed on from child to child without interruption until the bees reached the buzzing place where I myself was standing.

  This sketch of the grounds of Down House shows the part of the male bumblebee flight route studied by Darwin with the help of his children. What fun must have been to have him as a dad!

References

Freeman, R.B. (1968). Charles Darwin on the routes of male bumblebees. BULLETIN OF THE BRITISH MUSEUM (NATURAL HISTORY) HISTORICAL SERIES , 3 (6), 177-189.


Stiles, Edmund W. (1976). Comparison of Male Bumblebee Flight Paths: temperate and tropical. Journal of the Kansas Entomological Society., 49 (2), 266-274.

Tree bumblebee with foxglove

It is the 10th anniversary of the first recorded British Tree Bumblebee, a continental European species which crossed the channel on 2001, esblished successfully and has spread since to much of England. It's natural colonisation has been closely followed by Stuart Roberts, from the Bees, Wasps & Ants Recording Society (BWARS), who is collating a survey of this spread and has published an information sheet. The bumblebee is very easy to identify, with a tawny thorax and a black abdomen and a white tail. If you have any records you'd like to submit, check the website for more information. In my area, the tree bumblebee is doing really well and it is one of the commonest species at the moment. You can see them foraging on Ceanothus, cotoneaster, brambles and snowberry flowers. Today is the first time I have encountered them feeding on Foxgloves. This individual visited several spikes in succession, given me the chance to get a shot.

Rowan Feast

During the short period of time each season that a plant or tree is in full bloom they become a magnet for bees. This is the case of the rowan in the garden these days. Its flat, white inflorescences offer a white background for photos, but in many cases they are too high for close shots. Bees will pollinate many trees - for example holly and horse chestnut - but observation is even more difficult. The first Bombus hypnorum workers of the year were collecting pollen in our tree. Other bumblebee like B. lapidarius, B. pratorum and B. pascuorum will also forage on this tree. Many Red Mason Bees and a collection of hoverflies also feasted on the rowan today. Above, Helophilus pendulus, the footballer hoverfly.

This female Red Mason bee about to land on the flowers is showing its pollen basket under her abdomen and the little "horns" on her face that help her collect mud and make her nest partitions.

A Bombus hypnorum worker with a heavy pollen load.

Spring gallery

It has been quite warm today, 18.5 oC! A great day to start spring, the garden was buzzing and there was a lot of "firsts" of the year. One of those days it is hard to choose what to blog about. I saw my first butterflies of the year, a Red Admiral Peacock (in flight), a Small Tortoiseshell feeding on willow and a male Brimstone; first queen wasp; first pair of 7 spots mating and my first photo of a ladybird taking off. Also, first Bombus hypnorum, B. hortorum and first female Anthophora plumipes. The following shots are the best of the day.

A fortunate consequence of 7 spot ladybird communal hibernation is that you don't have to look far for a partner when you wake up!

A groggy queen wasp landed on yellow plastic 

And a hyperparasitoid flightless wasp, possibly Gelis sp. which looks rather like an ant walks on the blue bin

Philodromus spider sunbathing 

The first female Anthophora plumipes leaves a daffodil, which has marked her back with yellow pollen 

A male A. plumipes briefly resting on a buddleia trunk. Males look velvety this early in the year. They have been patrolling the garden since the 11th of March

 A Pholcus spider on the outside toilet looks much fatter than yesterday, after enjoying her spiderly meal.

A Harlequin and a 7 spot look like they are playing peek-a-boo

B. hortorum visiting Hyacinths