Sunday, 17 May 2009

Anthophora plumipes, a final post (I promise!)

Female A. plumipes feeding on Lithodora. She has got a mark of yellow pollen on her back, probably from the nearby broom. 
I realised a couple of days ago that I hadn't seen A. plumipes for a few days. Oh no! it's not possible spring is over! I thought. Yesterday I saw a male and a female and today a couple of females so, no, they are still around. I have a few notes about them I gathered these last few weeks. 
 I put together a phenology graph.
This includes just my records for this year in Hull. It illustrates the early male appearance and the segregation of male and female observations. In previous years, my earliest male record was the 10th of March 2007. The earliest female on the 21st of March of the same year. They are around for less than three months.
Male A. plumipes at the end of May. It has lost most of his hair and is barely recognisable.
 I have also compiled the flowers visited by this bee in and around my garden.  In March, the bees visited almost exclusively three plant species: Grape Hyacinth, Rosemary and Pulmonaria. Their emergence appears beautifully matched to the start of flowering of these species. At the end of April, the bees visit at least 11 plant species.
To end, I managed to get a few photos of Anthophora plumipes' cuckoo bee, Melecta albifrons. It visited my garden a couple of days of early may and fed on lilac blossom. 
Melecta albifrons sunbathing.

Thursday, 14 May 2009

Darwin on bumblebees: the quick and clever workmen

We could be tempted to think about insects as little 'robots', behaving blindly and rigidly responding to external cues following an internal instinctive program. However, in the last few decades, research on insect learning has taken off providing an astonishing amount of data on the behavioural plasticity and learning abilities of these animals. Much of the research has taken place using bumblebees as models as they can be easily kept in the laboratory and many individuals can be produced and used in experiments. Bumblebees, as social bees, have a rich behavioural repertoire. After emerging from their natal nests, queens explore their environment to find a suitable nesting site, feed themselves with nectar and pollen, build their nests, make cells, lay eggs and provision their offspring with more nectar and pollen. Foraging involves taking decisions as to which species of plant and which individual flowers to visit, the available flowers changing continuously as the season progresses or from site to site. In addition, not all nectar and pollen is easy to collect: in many nectar-rich flowers, nectar is located deep inside the flower (e.g. Honeysuckle, Nasturtiums) and pollen from different flowers has to be gathered in various ways. Recent studies illustrate the flexibility of individual bee learning, but also the less known aspect of social learning: bees not only learn on their own (from trial and error) but also from each other - and even from other species. Despite the flurry of recent research, many of the facts had been observed and hypothesized by Charles Darwin over a century earlier. Darwin never ceases to amaze me: he was a meticulous, keen observer, paying attention and being enthused by the littlest things; never ceasing to test hypothesis, clearly illuminated by his encyclopedic knowledge in all things related to plants and animals. He gathered observational and experimental data painstakingly, often in his own garden and sometimes even enlisting his own children.
He wrote on social learning:
"One day I saw for the first time several large humble-bees visiting my rows of the tall scarlet Kidney Bean; they were not sucking at the mouth of the flower, but cutting holes through the calyx, and thus extracting the nectar. I watched this with some attention, for though it is a common thing in many kinds of flowers to see humble-bees sucking through a hole already made, I have not very often seen them in the act of cutting. As these humble-bees had to cut a hole in almost every flower, it was clear that this was the first day on which they had visited my Kidney Beans. I had previously watched every day for some weeks, and often several times daily, the hive-bees, and had seen them always sucking at the mouth of the flower. And here comes the curious point: the very next day after the humble-bees had cut the holes, every single hive bee, without exception, [...] sucked through the cut hole; and so they continued to do for many following days. Now how did the hive-bees find out that the holes had been made? [...]  I am strongly inclined to believe that the hive-bees saw the humble-bees at work, and well understanding what they were at, rationally took immediate advantage of the shorter path thus made to the nectar." (Darwin, 1857)
And on the use of experience and memory:
"I observed also bees flying in a straight line from one clump of a yellow-flowered Oenothera to every other clump of the same plant in the garden, without turning an inch from their course to plants of Eschscholtzia and others with yellow flowers which lay only a foot or two on either side. In these cases the bees knew the position of each plant in the garden perfectly well, as we may infer by the directness of their flight; so that they were guided by experience and memory." (Darwin 1876)

A fragment of a description of social learning in bees by Darwin in his work "The effects of cross and self fertilisation in the vegetable kingdom" (1876)
A recently emerged Bombus lapidarius queen feeding on Agapanthus
A Bumblebee Bombus terrestris, worker gathering pollen from a poppy
All of Darwin's work, books, articles and letters are now freely available and fully searchable online in The Complete Works of Darwin Online.
Social learning in insects, a recent summary

Tuesday, 12 May 2009

Invertebrate macro photography

Painted Lady enjoying the sun
I thought I put together some details of how I take the photos I post in this blog. Unless otherwise stated they are all my photos. I actually started using my digital camera as a recording device. It is much easier to go to a photo and ID a bug than to try and remember it. Until 2009 my camera was a Canon Powershot G6, portable and with a superb macro. I have often considered going for a dSLR. I used to have a lot of - non digital - camera gear, macro lenses, flash arms, etc, but the advantage of the semi-pro G6 is that you don't have to carry stuff around, they are very light and you still get pretty decent photos. The quality of macro (and the 'supermacro' mode) in this camera is widely recognised and amazing value for money. I am a self-tought photographer, reading around and with trial and error I came out with this little collection of bug-photo hunting tips.
No flash
Personally, I am seriously alergic to flash. I love the look of photos with natural light and it is also less disturbing for your subject. Also, if you value portability taking macros wiht a flash would mean to get a flash arm, so, in this sense for me is also impractical. This of course is more challenging and means that many photos are not as good as they could have been with flash, and limits the photos you can get with poor light conditions. I actually don't take many photos in the winter, as there are not so many bugs around so it's not too bad.
Get close and personal
I like to see my subject eyes, so, I often go level with my beasts, with is often ground level. Some species do have bright patterns when photographed from above (butteflies, hoverflies), but all come into their own when photographed eye to eye
A Common Rough Woodlouse, Porcellio scaber
Know your subject
Finally, you do need to get very close, so you need to get some idea of how different invertebrates react to you. Some do not seem to react at all, making exemplar models (for example, garden spiders). Many do only react (negatively) to being exposed to the light and run away as fast as they can when you uncover them (centipedes, woodlice); others do show some avoidance behaviour when approached or normally move quite fast (butterflies, dragonflies). In any case, slowly approaching your subject won't do any harm. Only in very rare instances will the subject actually come to you to get his/her photo taken.
Zebra Spider, Salticus scenicus, looking at the camera
Hold your hand steady
If you can, rest your hand on anythin solid that happens to be close to your subject - ground, trunk, wall, rock - this will reduce camera shake and will result in crisper images in poor light conditions, when shutter speed is slow. The point is to keep your hand steady when pressing the shutter. Some people become aware of their own heartbeat and claim to shoot between heartbeats. I am just happy to hold my breath when shooting.
Azure damselfly
Shoot, shoot and shoot
When you are in a position to shoot, do not think twice and keep taking photographs if your subject allows. I start by taking some distant shots in normal mode. Then I get closer little by little. A poor quality distant shot is often enough for identification purposes. There will be time to delete, edit and label over the long, dark winter!
Garden ants on Peony bud
Choose your background
Blackground often makes the difference between a great and an OK photo. You don't have to move your subject. Most of the time changing the angle at which you take the photo will do. On the photo on top, taking a photo from the side of the bud would have shown a house in the background. A top to bottom shot just adds a green background and makes the wine-red of the Peony petals stand up.
Ectemnius hunting hoverflies
Show behaviour
Macro becomes very interesting when it shows the animal doing something. The photo above shows some behaviour but is also an example of a poor background, my son's blue plastic car. Doh!
Powershot G10
My recent upgrade has been to a Powershot G10. I thought about it a long time (I had started considering the G9, but the G9 came along. Its macro lenses do not allow for Supermacro and you have to change the zoom if you get closer to your subject, but the 15 megapixels leave room for quite a lot of cropping. I did some comparisons and I was satisfied I was actually getting better photos with the G10. It is even smaller and lighter than the G9, with a larger, brighter LCD screen, so now I actually carry it with me at all times.

Monday, 11 May 2009

Darts for love

I must apologize as so far my posts have been solely about insects. I hope this one will change the trend. A couple of days ago I saw the first mating Garden Snails (Helix aspersa or Cornu aspersum) of the year. It's been quite a long, cold winter and a dry spring, so, garden plants have been enjoying quite a long snail-free season. Snails have now come out of their winter dens under stones, behind tiles and in general dry places around the garden and are meeting each other ready for reproduction. Garden snails are hermaphrodite, that is, they produce sperm and eggs, but they only rarely self-fertilize, instead they mate several times over spring and summer (in my garden I've seen copulating snails from early May until the end of August. Mating is a reciprocal long-winded affair, the pair of snails exchanging sperm simultaneously. An remarkable aspect of courtship in snails is that it involves the shooting of a relatively large, calcareous, thin and sharp 'love dart' from one snail to its partner before actual copulation. The purpose of this violent affair was poorly understood and debated for a long time. The dart is not a requisite for successful mating (apparently, snails often 'miss') and not all the individuals shoot or a physical stimulant for copulation, as previously assumed. It became apparent that snails shooting their darts effectively had higher success fathering the offspring of the other snail. Recently, research has shown that the dart should be instead called 'the needle': the dart allows mucus to be injected into the other snails head: this mucus contains a chemical that inhibits sperm digestion (apparently, without the dart most sperm is digested), and therefore allows the shooting snail to father more offspring. Therefore the dart is an evolutionary result of sperm competition.
Mating garden snails, the snails on the right has been darted.
Snail laying eggs
Snail eggs

Sunday, 10 May 2009

Nomada bees

A female Nomada cuckoo bee
Something that never fails to surprise me, is that once I have a name to some beast or plant, I start to come across it more often: Learning allows you to see. This happened to me recently with Nomada bees. Before I had an ID I thought they were some sort of wasp. I had seen them often in my front garden. A few days ago I came across three of them, loitering around a crack in the pavement on a south facing garden in my street and got a few shots. Why wouldn't I identify them as wasps? They are almost hairless, slender, with a thin wasp-like waist and neat black and yellow striped abdomens. Again Wild About Britain, my favourite wildlife forum, proved me wrong. The wasps were in fact, cuckoo bees of the genus Nomada. This is a very large genus, worldwide over 800 species (around 30 British sp.) which mainly cleptoparasitise bees of the genus Andrena,  particular Nomada species tend to be host-specific, that is, they specialize in parasitizing a single Andrena species. Note I wrote 'cleptoparasites', what means is that they actually lay their eggs in nests of bee species, on the pollen supply intended for the developent of the bee larva. Nomada males and females are often found around their host nests. Males waiting for females to emerge and then mate with them. The females lay their eggs in cells being provisioned by the host. Their larva kills the host larva and eats the pollen provision during its development.
 Research into Nomada chemical communication has revealed a complex, puzzling system in which some of the hosts chemicals are also produced by the parasite. Nomada males produce chemicals identical in composition to secretions of the female Andrena species they parasitize which they use to line their nest cells. Why is the male and not the female which produces this chemicals is not know. It could be that upon copulation the male parasite transfers the secretion to the female and thus she can enter the nests with a chemical 'camouflage'? Is this to show the female the right species' nest? Both explanations seem feeble, as it would seem simpler that both sexes would learn the odor of the nests they grew in, and that females could in theory produce the smell themselves if that renders them less likely to be attacked in the host's nest.
 The particular Nomada species in our front garden seems to be N. marshamella, which parasitises several species of Andrena (A. carantonica, A. scotica, A. trimmerana, A. nigroaena). Some of these nest communally in hole or cracks in pavements. So, all this fascinating chemical communication and tales of robbery and killing might be happening, literally, just outside your front door.
Two Nomada bees waiting at the entrance of an Andrena nest.
This one is about to enter the nest
Andrena bee resting (possibly A. carantonica). This genus is not only parasitized from Nomada cuckoo bees, but males are also deceived by orchids!

Sunday, 3 May 2009

Osmia rufa update

The new bee post has been a great source of both entertainment and frustration (lots of blurry shots of bees leaving nest!). Now females are very busy going in and out of the nests and we can follow live how each provisions the cells and finally blocks the nest entrance with dark mud. Today three cells had been finished. The bees feed all around the garden. They visit the apple blossom and the rosemary. A new development is that we have found the cleptoparasitic fly Cacoxenus indagator visiting the post - not yet entering nests. Not only have the bees been quick adopting the new bee post, but they have rapidly been followed by their parasites.
This is a selection of photos of the last couple of weeks.
A pair of Osmia rufa. Apparently, the male stays on top of the female for a while after mating. Note the smaller size of the male and the 'horns' on the face of the female
A bee about to leave the nest. It looks like a male
Another male inspecting a hole
Female starting to build the last cell wall
The wall is almost complete
The finishing touches
The finished nest
This little fly - same size and family than the fruit fly - is a cleptoparasite of Osmia rufa nests. It lays its eggs on the stored pollen in the cells.

An article with interesting photo of the inside of the nest
Another article with lots of info on associated fauna to Osmia rufa nests