Ivy bees in Hull

 I have spent some time watching mature Ivies lately. It is Ivy peak flowering season, and the couple last days have been warm and sunny, bringing the insects out, the ivies humming with insect activity. Droneflies, Red Admirals, Comma, Wasps, honeybees are attracted to flowering bees. I was actually looking for Green Mesh Weavers, on an Ivy in an untarmaced tenfoot (alleys between houses) when I noticed two stripy bees rummaging around the leaf litter at the bottom of the ivy. I couldn't believe they were Ivy Bees, Colletes hederae! I have previously seen Ivy Bees in east Yorkshire, at North Ferriby and at Flamborough, but I thought we wouldn't get them in Hull due to our clay soils, as this bee needs loose soils for nesting. 

Two bees exploring the soil under the ivy, this is probably loose enough and sunny enough for a nest site?

A winner from climate change

Ivy Bees started colonising the UK from 2001, after expanding in northern Europe, and in the last couple of decades its distribution range has rapidly expanded northwards, with the first Scottish records coming in 2021. The mail pollen source for its larvae is Ivy, and the bee flight period coincides with the flowering season of ivy, from September to early November, with a single brood. They are solitary bees but they tend to nest together, sometimes forming large nesting aggregations in suitable habitat. Females will excavate a nest and line the walls with a cellophane-like substance, which explains another name of the bee, Cellophane Ivy Bee. Ivy pollen is brought to the nest and an egg is laid atop a mound of pollen, before the cell is sealed and another load of pollen is collected for the next egg.

One of the Ivy Bees near the ground after some exploring.

A female laden with pollen having a rest to clean its tongue.

A foraging female showing the banded abdomen. This bee is relatively large, the size of a honey bee, with orange hairs on the thorax, and contrasting broad buff bands in the abdomen, unlike its close relative the Sea Aster bee, which is smaller and has a white banded abdomen. Habitat, timing and foraging flowers can also help distinguish these bees.

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.

The knapweed bee

A few years ago I introduced some native knapweed in the garden. I planted them on the beds and they did well. However, the following year they didn't come back on the beds, they selfseeded in the cracks in the cement and now I have several large plants growing amongst pots from the cement. They attract many bees, but one in particular, enjoys this plant the most, the small mason bee Osmia leaiana. Males are beautiful golden bees with green eyes, while the females are dark, with an orange brush of hairs under they abdomen, which they use to collect pollen. They often dive head first into knapweed inflorescenced and their orange underside becomes quite visible.
 Today I was very pleased to find out these bees are using my bee hotels, I hope to get some photos of the cells they are stocking soon.

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.