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.

The nest robber

I was puzzled when I checked the bee hotel a couple of days ago. The painstaklingly, lovingly filled nesting cells of the Osmia leaiana nest that illustrated a post a few days ago were gone. There was pollen everwhere and the nest walls made of chewed leaves weren't there. A Megachile willughbiella female, a leafcutter bee, was inside, rubbing its scopa against the walls. Was she the reason for the disappearance of the smaller mason bee's nest or just taking advantage of a previous nest predator?
 Although I'll never know for sure, I think that the leafcutter is probably to blame. There are plenty of empty cavities in the bee hotel, but she apparently decided that this was a better hole than the rest and probably fought the mason bee out of her nest (Leafcutters have formidable scissor-like jaws, and this leafcutter species is a large bee), and then proceeded to empty the contents, eggs, pollen, nectar and walls to make space for her cells. Today, the leafcutter had completed her first cell (above). Note that the walls are still covered in yellow pollen.
 The bee nestbox is providing plenty of surprises and allowing observations very difficult to make in natural holes. The events illustrated here remind me that competition is fierce out there, although in the case of hole nesting bees, it will pass unnoticed in the darkness. Many bumblebee queens are ousted from their nests by other bumblebee queens, not necessarily from cleptoparasitic species, which take over after a fight. In solitary bees and wasps, suitable nest holes might be limiting and intra and intraspeficic competition might be rife, although fights may often take place inside holes. Watch this fascinating video of three bees fighting for a nest hole by George Pilkington, and this series of photos by Simon Saxton documenting two Ectemnius wasps fighting for a nest hole. Nest lining thicker end walls provides physical defence, and might not only protect against cleptoparasitism, but also against other bees taking over, stealing the nest hole and destroying the nest contents.

7th of July. A female Osmia leaiana working on her nest. Note the remains of last year's leafcutters nest in the cavity under it.

16th July, a female leafcutter emptying nest contents by scooping pollen.

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

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.