Sharp-tail bees

It has been a while since I've seen a new bee in the garden. A couple of days ago it was sunny and warm and I watched the first male leaf-cutter bee Megachile willughbiella on a geranium. A while later a bee was basking on top of the fence post and I managed some distant shots. Its jaws looked very leaf-cutter like, but the end of the abdomen had some tell-tale spines, indicating it was a sharp-tailed bee Coelioxys sp. a bee I've only seen rarely in the local wildlife garden.
Although males and females sharp-tailed bees can be found nectaring at flower sources, they are cuckoo bees. The females do not collect pollen, instead, they are cleptoparasites, looking for ready made cells already provisioned with a pollen load. Their usual hosts are leaf-cutter bees, and their common name derives from their tapered abdomen of females, ending in a fine point, which is able to slice through the leaf wrappers of leaf-cutter bees, laying one egg either under the pollen load, or in between layers of the leaf wrapping of the cell before the cell is sealed. The cuckoo bee will also match the sex of her eggs to the host eggs sex, with the male eggs positioned in the outer cells of a nest. Once the larva hatches, they use their large mandibles to kill the host larvae or any other competitors. The cuckoos larvae complete their development and emerge at the same time as their hosts.
  I find the male abdominal spines very intriguing. What is their function? Coelioxys belong to the same family - Megachilidae - than Anthidium manicatum, the wool-carder bee, whose males are armed with formidable abdominal spines with a similar disposition. Male wool carder bees use these spines as weapons to defend their flower territory from other males and also other bees. They can fearlessly attack honeybees and large bumblebees, and are capable of killing them. It is unlikely that sharp-tailed bees use their spines in a similar way, as females do not collect pollen and there is no flower resources to defend. In the monograph Bees of the World, by Charles Michener, he hints at the spines being involved in dealing with the modified female's abdominal tip during copulation.
 There are eight species of sharp tailed bees in the UK, but in general they are very hard to identify without a specimen, so I will have to content myself with not having a definite identification for now.
 I have gone through my records of this genus in the wildlife garden, just five of them in June and July and here I show some record shots.

A male Coelioxys feeding on sage (12/6/10)

Female Coelioxys on birds-foot trefoil (4/6/2011).

Male Coelioxys resting. Many bees hold on with their mandibles in their sleep (10/7/2009).

Female Coelioxys on marjoram (2/7/2011).

Male Coelioxys on meadow cranesbill (11/7/2011).

Cuckoo bees tend to be rare bees, and sharp-tailed bees are no exception. The presence of cleptoparasites indicates a healthy host population. Often cleptoparasites decline and get locally extinct when a host population declines. In a study on sharp-tailed bees, about 3% of over 14,000 host cells (Megachile inermis) contained Coelioxys funeraria and less than 10% of Megachile relativa were parasitised. So, what about the hosts in my garden? The bee posts and bee hotels are commonly used by leaf-cutter bees of at least two species in my garden: Megachile willughbiella and Megachile centuncularis, used as hosts by several British Coelioxys species. Some species of Coelioxys are thought to parasitise Anthophora furcata, which is also a regular bee foraging and possibly nesting in the garden log piles. The synchrony of the hosts is remarkable as both male leaf-cutters and A. furcata, appeared in in garden in the last couple of days too.

This was the first of the year A. furcata in the garden, a male yesterday.

Male M. willughbiella, 29th May.

Male Megachile, possibly centuncularis, yesterday.

More information
Scott, V. L., Kelley, S. T., & Strickler, K. (2000). Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America, 93(4), 941-948.

Michener, Charles Duncan. The bees of the world. Vol. 1. JHU Press, 2000.

Falk, Steven and Richard Lewington 2015. Field guide to the Bees of Great Britain and Ireland. Bloomsbury, London. 432 pp.

A solitary bee quartet

I had so many wild things this summery sunny day that if was hard to settle for an invertebrate group to feature. For lunch I went out with fellow wildlife-lovers Robert Jaques and Callum MacGregor, and tried to capture some hoverflies. Hoverflies were indeed a good candidate for my wild group today as there were plenty, and of many species. Many males were hovering, but a couple of Myathropa florea males managed to sit on my hand, Robert's shoulder and Callums head and avoid the insect net altogether. Episyrphus balteatus, the marmalade fly, were also hovering, and the beautifully metallic Epistrophe eligans. Then I spotted a new spider, with a caterpillar on its web, and then another, would I feature spiders? Then a Red Mason bee started feeding on Buttercups, maybe a wild solitary bee day?

Female Red Mason bee, Osmia bicornis on buttercups. One of her 'horns' is visible at the front of her head. She uses its horns to mould mud she uses to seal her nest.

 Later after work I popped in for ten minutes in the wildlife garden. It was quite warm at the time. A leaf-cutter bee was feeding on thyme, and then chives. Its white and golden mittens flashed as it fed, a Willoughby's leaf cutter bee. Definitely a solitary bee day!

Male Willoughby Leaf-cutter bee, one of the easiest to identify by its front legs, which are covered on white-golden hairs in the shape of mittens, just visible here.

Back home I went to the sage. I had seen a favourite bee of mine yesterday very briefly. Anthophora furcata, a male which didn't settle, patrolling around the sage and the hedge woundwort. This is a rich brown bee with a very long tongue. Males have a yellow face and they have a strong preference for hedge woundwort, but also like several others flowers with deep corollas. Males appear, as many other bees, earlier in the season, settle in an area with their favourite flowers and check other bees, often head-butting them, while in search of females. And there he was, lovely and fresh. He even stopped the frantic patrolling to settle on a sage leaf to bask for a while, its back and face covered on pollen.

A male Anthophora furcata.

As I watched the A. furcata, a smaller bee caught my attention. It was a female Osmia caerulescens. This is a long tongued bee too, females have a bluish tinge and white hairs on stripes on its abdomen. After feeding on the sage, the bee stopped and stretched its tongue several times.

Female Osmia caerulescens

A female Osmia bicornis in the garden on the wallflower Erysimum 'Bowles mauve'.

If you'd like to learn to identify solitary bees, the Bees, Wasps and Ants Recording Society is a wonderful resource. Identification sheets for common solitary bees, often found in gardens are available too. There are 205 species, many hard to identify, but a few common ones are easy to identify once you become familiar with them.

Bee hotel guests

Bee hotels are very popular at the moment. Most garden centres sell them, and they are advertised as homes for solitary bees. Solitary bees do use these bee hotels to make their nests, but once you get guests, how to tell them apart?
I was inspired to write this post after a twitter exchange starting with this message:

There appear to be about 225 species of solitary bee - think id unlikely!!! But so pleased something is using bee box :)
— Ragged Robin (@CarolineIrwin3) July 13, 2013

 With this post, I hope to give you an overview of what species of bees are likely to use bee hotels. In fact, only a small number of the over 250 species of solitary bees in the UK are likely to use bee hotels, so, with a bit of patience, identification is likely. For a start, not all solitary bees use bee hotels as they do not nest in cavities. Many solitary bees nest in the soil (the mining bees), others prefer the mortar of walls, or dig their nests in dead wood, or prefer much smaller holes or crevices than those provided in commercial bee hotels, which are usually made out of bamboo or reed canes. Mind, you, many more solitary bee species will be found in your garden than the ones that use the bee hotel. Once a female bee choses a tube in the bee hotel for nesting, you are likely to notice some activity, as she stocks the nest with nectar and pollen, lays eggs and builds partitions between the cells where her offspring will grow. Once she runs out of space in one tube she makes a stout plug and may start to fill another tube with more cells. The males searching for females or patrolling the area of the bee hotel can also bee noticeable.
 In addition to bees, other insects like some digger wasps or the cuckoo bees or flies that parasitise the bees themselves or spiders will also be seen on or near the bee hotel. My experience is on the north of England, and with home made bee hotels made by drilling holes in pieces of wood, so it is likely a few more species will be found to use bee hotels in the south.
 For identification purposes, time of the year, general size of the bee (use a honeybee as a guide) and colour patterns are useful. Also, it is very helpful if you can check what the bees are carrying as nest materials and the colour of the brush of hairs under the bees' abdomen that they use to carry pollen. The material of the plug covering the finished nests can also provide information as to what species built it. Once you can recognise the species or species group of the bees using your hotel, they are bound to provide an endless source of fascination, and bee watching may be addictive, so make sure you place your bee hotel in a spot you can easily and comfortably watch at close quarters!

Red Mason Bees
These are likely to be the first bees in spring using a bee hotel and the most likely species to use bee hotels. The bees are active from March to May. The females are reddish, with large, black heads, and size similar to honeybees. They have characteristic 'horns' on their faces, which they use to mould mud (above). Males are also reddish, smaller and with a white moustache. Males often sit on or near the bee hotel, sunbathing and looking for females.
  Mason bees use mud to partition cells in the bee hotel holes. They will travel from the bee hotel to the edge of ponds where they fetch mud, a little pellet at a time. Click here for more posts on Red Mason Bees in BugBlog.

Blue Mason Bees
These are much smaller bees and there are two similar species, Osmia leaiana and Osmia caerulescens (the blue mason bee proper). Males of both species are metallic green. They like to sit on the nest or stones or leaves at low level to sunbathe and from there they do patrolling flights in search of females. The females are metallic dark blue with a dark pollen brush underneath (O. caerulescens) or dark brown with an orange pollen rush (O. leaiana, above). Both species use chewed leaves to partition their cells.

Leaf-Cutter Bees
These are high summer bees, flying from mid May to August. I have two species in the garden, a large one and a small one. There are other common species in the UK, so care should be taken with identification. The male of the large species, Megachile willughbiella, is easier to identify, as it sports white-golden mittens on its front legs, which are very visible as he sits on the nest or sunny spots and grooms himself. Other identification features are the colour of the pollen brush on the underside of the abdomen: either orange (in the smaller species M. centuncularis, above) or red and black in M. willughiella (below). It is worth checking your bee hotel in poor weather, as these sun-loving bees like to use it as shelter in cold or wet conditions. More on leaf-cutter bees in BugBlog.

 Female Megachile willughbiella. Note the red and black brush of hairs under abdomen

Megachile willughbiella male. Note the pale 'mittens' on his front legs.

A few photos of the looks of the finished nests follows.

Two M. willughbiella males with two Osmia rufa (grey mortar looking) and a O. leaiana/caerulescens at the top, which is made of chewed leaves). 

A completed nest of a leaf cutter bee, Megachile. They use circular sections of leaves to make their nests.

Two recently completed nests of Osmia leaiana/caerulescens (I suspect the former, which in the last few days has been feeding on knapweed). Photo taken today.

The same area of the bee hotel on the 11th of May, just an Osmia rufa nest had been completed then.

Other bees that are known to use bee hotels in the UK are Chelostoma florisommne and Chelostoma campanularum, other Megachile species and Ectemnius digger wasps.

Ectemnius sp. a digger wasp, emerging from its nest.

More on Bee Hotels
Buglife.
Bees Wasps and Ants Recording Society.
Natural History Museum

Bees by behaviour

Summer finally arrived a dew days ago, and the bees have been enjoying the sunshine and warmth. I have been busy beewatching. It struck me that although there are hundreds of birdwatching books available, 'Beewatching' is not a shelf you will find in your trip to the library: number of beewatching books: nil, zilch, zero (sorry, no, I do not mean beekeeping). But why? Although bee watching has challenges, it is immensely rewarding. Plus points: (1) you can do it from the comfort of your garden, in fact gardens are amongst the best habitats to observe bees, as many flowers are available and you can pop out when weather conditions are optimal, therefore, no transportation needed (2) no binoculars or telescopes are necessary, and, (3) with a little investment on garden plants or a home-made bee hotel, you can be rewarded by new species coming to you and behaving as they do in the wild and even breeding in your garden: even small urban gardens can attract a large number of species. Given the lack of field guides on the topic, beewatchers are forced to made themselves out of experience, plenty of patience and readiness to learn. Although many bee species can only be identified under the microscope, some common garden species are relatively easy to identify while they are going about their business. I hope to show here that you can narrow down the group of bee or even identify to species level solitary bee species just by watching the various activities they are engaged with. 

Watch the flower

Many bees prefer to visit particular flowers. Some bee species are oligolectic, which means that they gather their pollen from one or a few flower species, others called polylectic, collect pollen from a wide variety of flowers. But even if the bees are polylectic, they often show some degree of preferences, therefore noting which the flowers they are visiting makes it easier to identify bees. This works even for males when they are patrolling and not feeding, as the males will check out the flower species that the females visit for nectar or pollen. A male Anthophora furcata, today, checked first one patch of Stachys sylvatica, then Lamium maculatum, then the other Stachys sylvatica patch. Surely, a female appeared later (below) to collect pollen in S. sylvatica, and the orange pollen she was carrying was probably from Lamium.

 Wool Carder Bee females are likely to be spotted shaving Lamb's ears (Stachys byzantina) hairs or feeding on the flowers. Megachile willughbiella loves cranesbills, campanulas and everlasting peas. Anthophora plumipes is strongly attracted to Lungwort and Comfrey. It also works the other way round: some plants are visited only by a reduced number of species: only a handful of garden species will visit foxgloves or honeysuckle.

Pay attention to detail
A large male bee patrolling campanulas is probably a leafcutter bee, Megachile willughbiella. To make sure, follow him as he flies, as he will settle regularly in a sunny, exposed place after bouts of patrolling (below).

Watch him carefully when he stops, he will almost invariably groom his head with his front legs a couple of times after landing - why? maybe wiping his eyes clean? -, and his white 'boxing gloves' will be visible even from a couple of meters away. If you can get closer, crouch down and look at him straight in the eye: he is all concentration, watching for females, rapidly twitching his head looking left, right or up. He does this for a few seconds and then flies off to carry on patrolling.

Leaf designing
A little bee flying from leaf to leaf, settles and walks sideways along the edge of the leaf briefly, like she is checking it, flies to the next leaf and then starts cutting an oval shape piece with her jaws.

Just finishing cutting the piece. Note that the same leaf has two other cut pieces.

In this shot you can see how she is holding the rolled piece of leaf with her legs and jaws

The edge of most leaves of my Enchanter's Nightshade plants, are all cut out. The culprit is the aptly named leaf-cutter bee, Megachile centuncularis. Leaf cutter bee females collect hundreds of leaf fragments to line their nests. As she cuts a fragment, she rolls it under her body using her legs and when she is finished she also holds it with her jaws before she flies up and then straight to her nest. If you can check the underside of her abdomen as she cuts the leaf, you will see the golden brush that characterises this particular species.

Spot the bully

I watched the first Wool Carder Bees of the year a couple of days ago in the local wildlife garden. Two males patrolling and feeding in a patch of Betony.

These are large, powerfully built bees, armed with five sharp prongs at the end of their abdomen. Males are territorial and they will readily attack and expel from their territory any other bees - even big bumblebees -, monopolizing the females that come to feed at their patch. When they rest, they keep their wings open at an angle, with their abdomen exposed. One of the males attacked a Bombus pascuorum feeding on the betony, and the bumblebee swiftly flew away.

Bottoms up!

Watch how the bee feeds on a flower. Leaf cutters (Megachile species) carry their abdomen tilted up, especially females, and rotate on the flower collecting pollen (see top shot). Look under their abdomen, you will see a broad brush of hairs. The color of the brush can help identify the species. They collect pollen on their rear legs and transfer it to the brush as they move over the flower. Megachille willughbiella females have a red and black brush, while M. centuncularis have an all golden one. Note that the hair color can be obscured by the pollen! This little video I took earlier today shows how she collects pollen on knapweed, a current favourite plant for bees in the garden.

Don't forget the little ones

Many bee species are small, you might have taken them for small flies in the past, but now that you are watching flowers up close you start to notice them. These two photos show flower preferences in two small Osmia species, which I only found in the garden this year. How could I have missed them before? 

Osmia caerulescens, the Blue Mason Bee, likes labiates like French Lavender, Sage or hedge Wouldwort

Osmia leaiana loves Knapweeds

Watch the seasons
Solitary Bees fly during relatively narrow periods, maybe two or three months in the species that have a single generation per year, so the time of year is often informative. Anthophora plumipes flies from March to early June, whereas Anthophora furcata has a short flying season in June and July.

There is so much to learn
As you become a beewatcher, you will develop a thirst for learning about the lives of these little critters that share your garden. For some of the species there is little information available, even common species have structures or behaviours that still remain enigmatic (what is the purpose of Megachile willugbiella boxing gloves or Anthophora plumipes hairy legs? why are the scopas of bees different colours, do they provide information to other bees, maybe when mating?). There are some resouces that I treasure, like my Bees of Surrey book by David Baldcock, or the BWARS site, and various bee identification forums, but as these are mainly concerned by identification and recording, I still want a beewatchers field guide.

Shelter and food for a cold leafcutter

I pity the leaf-cutter bees on cold or wet days. They really are sun-loving bees and when the weather is not to their liking they hide in the bee hotel, peeking out of the holes, hoping for the sun to appear. I found this cold male Megachile willughbiella clinging to a hardy geranium flower after a shower a few days ago. Geraniums are one of their favourite flowers, and they also makes a handy umbrella.

Leaf-cutter bee antics

There has been a lot of leaf-cutter bee activity in the last week in the garden. Females collect nectar and pollen from Campanula, wild rocket (female collecting pollen above), everlasting peas, and birds foot trefoil. They have colourful pollen baskets underneath their abdomen.

 Males patrol the females' favourite nectar and pollen sources. Here a male Megachile willughbiella, easily recognisable by their white-golden mittens and moustache, flies by everlasting pea flowers.

They also keep a close eye on the bee hotel, where, for the first time, I have seen nesting activity, and often bask on top of it or nearby on sunny spells.

Males of Megachile willughbiella also "sleep" in the hotel, or seek refuge during cold or rainy spells. On the photo above, two males settle for the night. The plugged nests around them belong to Osmia rufa, the red mason bee.

When they detect a female feeding, males hover in front of them for a little while before attempting mating. The following description is for Megachile fortis, an American species of leaf-cutter by John Neff and Beryl Simpson, may well apply to the british Megachile species:

 When a female was encountered on a sunflower head, the male hovered in front of the capitulum while the female moved around it, probing the circular array of florets. When the female reached the 1200 position (aligned vertically on the capitulum with her head up) he darted forward and grasped her with his fore and mid legs, rapidly curling his abdomen under the tip of her abdomen, apparently attempting copulation. Both bees then dropped from the flower with the female quickly escaping or being released to fly away and resume foraging. The period from pouncing on the female to release was quite brief, typically less than 3 seconds.

 Today I had the chance to observe a female Megachile willughbiella repelling a male. She was basking on top of the bee hotel and the patrolling male spotted her. He pounced on her but she curled her abdomen up as you can see in the photo above. The male flew away and the female adopted a more relaxed position. Leaf-cutter have very mobile abdomens and tend to tip them upwards. I have no idea why, but I wonder if it has something to do with their pollen collecting. However, males also have this tendency to raise their abdomens when feeding or just when preening themselves.
 I have posted before on these species leaf-cutting behaviour itself, but I had never had the chance to look at a finished nest from close up. Two nests were finished in the last couple of days in the bee hotel. As you can see below, nests come in colours. I wonder if the yellow one is made out of Potentilla petal sections.

Both species of leaf-cutters are nesting in the bee hotel, the smaller I believe is M. centuncularis and the large, M. willughbiella.

Here a female M. centuncularis, recognisable by her all orange pollen brush and marked white striped abdomen, works on the yellow nest.

Reference

John L. Neff and Beryl B. Simpson. 1991. Nest Biology and Mating Behavior of Megachile fortis in Central Texas (Hymenoptera:Megachilidae) Journal of the Kansas Entomological Society, 64: 324-336.

Two summer bees

The Summer season is quickly advancing this year. This week, Stachys sylvatica, the hedge woundwort, came into blossom and it has quickly being followed by the first Anthophora furcata males, which I saw yesterday visiting the sage, the foxgloves and Lamium maculatum. The previous two years I spotted the first males on the 7th and 10th of June, so the 21st of May is very early indeed.

Anthophora furcata male visiting sage

 The second summer bee is the leaf-cutter bee, Megachile. I think I have already seen the two species that visit my garden this year. The first one, a female Megachile centuncularis (tentative ID) cold on a Cat's Ears, Hypochoeris radicata, on the 16th of May.

Megachile centuncularis on Cat's Ears

The second, a just emerged male M. willughbiella, peeking out from its cell in the bee hotel, its white-golden gloves visible (top photo) on the 18th (top photo). A few moments later, a male was sunnying itself, stretching its abdomen, and grooming itself on a branch nearby and flying away into the wide world.

A fresh Megachile willughbiella male stretching its jaws and showing its white gloves

This small bee hotel -placed in a sheltered, sunny fence in the garden - has been very popular with bees this season, and many of last year's cells have produced bees. You can see the muddy remaining of the walls of last years nests around some of the openings in the photo above -, and several others have been completed this year by red mason bees, Osmia rufa, which are still active.

National Insect Week Gallery

I have been too busy writing down stuff I've been watching or compiling records, and generally watching bugs these last warm days to blog, but I have decided to put an end to this by celebrating National Insect Week (21-27 June) with a gallery of the bugs I have been watching. I hope you enjoy them.

Flies: This is a large hoverfly, Vollucella pellucens. I have been watching them today hovering and I tried in vain to get a good shot in flight. This one posed nicely for me though.

 Bees: I had a great time watching Anthophora furcata in my local wildlife garden. This female is gathering pollen from Stachys sylvatica.

 Butterflies: the first ringlet of the year. It was warm and this individual fluttered for quite a while before settling on the grass.

Moths: yesterday I spotted this Narrow Five Spot Burnet atop a Knapweed seed head.

And more bees: After cutting a piece of Circaea luthetiana, this female Leaf-Cutter Bee (most likely Megachile centuncularis) had to retreat and alight again as it couldn't fight the wind carrying the piece of leaf. After a while, it flew away to her nest.

A sunbathing Wool Carder Bee (Anthidium manicatum) female.

Beetles: A female Lesser Stag Beetle walking over some plants on a front garden yesterday. So far, I have only seen females in Hull.

More bees: A Bombus hortorum extends its long tongue before landing in a Digitalis lutea flower. This is the longest-tongued bumblebee in the UK.

A male Colletes daviesanus resting on an Oxeye Daisy flower and...

a female with loaded pollen baskets nearby.

To end, another bee (of couse) a female Anthidium manicatum feeds on a Geranium flower on the summer solstice.