The urban environment as a habitat for deadwood hoverflies

A recent record of a Callicera from the middle of South Woodham Ferrers reminded me of a long-lingering hobbyhorse. We pay remarkably little attention to trees in our streets and parks, and yet they must be ideal for many deadwood hoverflies. After all, many are regularly pollarded and this must create the conditions needed for rot holes. Other forms of damage will induce sap runs (Horse Chestnuts are especially prone to bacterial cankers and sap runs) and perhaps also decaying roots.

The presence of Callicera in various places, including suburban Wolverhampton, shows how rot holes can be important. There are records of Mallota cimbiciformis from central London parks and plenty of records of that ubiquitous urban species Myathropa florea.

It seems to me that there is therefore a strong case for research into the frequency of rot holes in urban trees and for an investigation into what uses these holes. Perhaps it is time for the conservation agencies to commission such studies? Maybe it could be done as a big ‘citizen science’ project? Whichever means is used, it seems to me that there is a need to develop thinking about the saproxylic biodiversity value of urban trees and to raise awareness amongst tree officers in Local Authorities.

Photographic records - some further analysis

As the winter races towards us the numbers of hoverfly photographs being posted on the web has greatly reduced. In mid summer I can spend as much as two hours a day extracting data. Today it took me ten minutes! And, for my troubles there were no new hovers but a couple of other fly families. I shall hopefully write the exercise up in detail for a peer-reviewed journal later this winter, but it is worth sharing ideas at a much earlier stage.

The number of records secured from websites and occasional records sent as photos by e-mail has just passed 10,000 and the number for 2012 has exceeded 3,000. The graph (Figure 1) tells an amazing story of how photo-recording has taken off. The rate of change is phenomenal, but what it does not show is the numbers of records that later come in from people who now maintain a separate record of what they see and send me a spreadsheet.  There are several people who now do this, so I don't need to extract their photo-data. Thus, there is a gradual transition from photo recorder to active recording scheme contributor. At least five people have made this transition and they now contribute significant numbers of records each year.

Figure 1. Numbers of records gathered from photographic websites over the period to October 29 2012.

Gaining a new active recorder is a great boost to the scheme and this can be exceptionally valuable when they make a note of everything they see. So much more can be done with big datasets and it is the relatively widespread or abundant species that are often useful for analysis of issues such as responses to climate change. Of course there are exceptions as I have previously shown with Volucella, but species such as Epistrophe eligans, Leucozona lucorum and Rhingia campestris all tell important stories about responses to environmental variables. That reminds me that Stuart and I really need to write up some of these formally!

As I highlighted the other day, photo recorders can occasionally turn up exceptionally important records and so I am keen to encourage new participants.  That is not to say that everything can be identified, but even if a confirmed ID cannot be given, the hint of a rare species' presence may be sufficient to get somebody to take a closer look at an area.

It is quite staggering just how many people do take photographs of wildlife and put them on the Web. ISpot has been exceptionally successful, but I find Flickr a very useful source too. My great regret is that around 50% of photos still have no details of where and when they were seen. So, if you take photos and place them on Flickr do put some data with them. Geotagging is great as I can usually find a 6-figure grid reference from this but even the name of the place is often enough to get a ten kilometre or one kilometre grid reference.

Figure 2. Numbers of recorders and the numbers of phot-records. One person has generated 1000+ records and one just over two hundred.

Relatively few people regularly photograph hoverflies as can be seen from Figure 2. But a few are amazingly prolific. I'm always delighted when I find a new active photographer but these days that is quite rare because I have spent so much time syrphing the net this year.

This graph shows how a relatively small minority regularly photograph hoverflies but that minority has made a very substantial contribution to the overall dataset. This is little different from the main data reaching the Recording Scheme where just 21 people contributed 50% of the data that was used in the last atlas.

Ash dieback

Publicity concerning Ash dieback has achieved remarkable proportions in a very short space of time. And yet why did it not figure three years ago? Had there been a ban on imports three years ago when the problem became apparent maybe we would not have the problem that is faced today? As it stands, the picture looks bleak and we face the loss of a major part of our landscape and its ecology.

Still, what is done is done. We have got to find a solution. There are obvious implications as Ash is a major element of the landscape. As I drove down to Long Crendon yesterday I found myself scanning the landscape for Ash trees. On the limestone this is really a very important tree both in a landscape and a broader ecological context. Ash woodlands are commonplace on the limestone and many support very rich assemblages of saproxylic hoverflies. So we face a major crisis.

From a hoverfly perspective maybe the way forward is to develop a strategy to provide growing replacements before we loose the Ash? If  so, which species should we use? I am amazed to say that I wonder whether we should be looking at Sycamore? Obviously there is a case to be made against Sycamore but it offers some important advantages:

• It is fast growing and appears to create dead wood situations similar to those that are offered by Ash.
• It seems to support sap runs with similar properties to those of Ash.
• The bark appears to have a pH that is favourable to many lichens.
• It will grow in many of the locations that can be expected to be vacated by Ash.
• It is not noted for its pests and is a vigorous, tough and fast growing species.
• It supports good numbers of aphids and potentially rot hole and dead wood hoverflies.

I never thought I would end up as an advocate for Sycamore, having spent much of the 1980s trying to eliminate it from the woodlands of Mitcham Common! These days I am focused on eliminating invasive bramble from acid grasslands but there is a bigger picture to consider. There is a major conservation debate to be had and we have a lot to think about. Ash is so fundamental to our rural landscape and its ecology that there is an urgent need to do some thinking about how to respond to this crisis.

Callicera spinolae

A recently posted photograph of a Callicera from South Woodham Ferrers caused me quite a lot of excitement.

 http://www.flickr.com/photos/rivercrouchwalker/8073739710/in/set-72157631737373239

Might it be C. spinolae? I suspected that it was as the date is right, but males are not easy to identify from photographs. I sent the link to Steve Falk who also felt this was the likely identity and posted accordingly.

Are we right? Take a look and see what you think - it will go into the Recording scheme with a slight level of caution attached. For me this is a good example of how a non-specialist can make a valuable observation - whether this is C. aurata or C. spinolae is somewhat immaterial as it shows how a rarely seen species can be picked up by casual observations.

Hoverfly training courses

For the past few years Stuart Ball and I have been running regular training courses in hoverfly identification. This year we are booked to run courses at Bristol, Carlisle, London (Roehampton) and Northamptonshire. We have a couple of other tentative bookings but might conceivably manage to schedule a further course if it is wanted.

The package we offer makes it relatively simple for a local Wildlife Trust or voluntary group to organise. We provide the microscopes, specimens, projection equipment etc. All the local organiser has to do is to find a venue capable of comfortably seating 12 people at microscopes.

We do make a charge for the course, but this is essentially to cover basic costs - fuel, overnight accommodation and food, plus the handouts. Assuming a venue within a 400 mile radius of Peterborough we usually manage to do the complete package for between £300 and £350, which if split amongst twelve people is around £30 per head.

The course is an introduction, but we are pretty confident that the majority of the class will be tackling hoverflies quite competently by the end of the weekend. Our approach is based on preserved specimens so it makes it possible to teach during the winter. We have found this to be the most effective way of getting people started.

Occassionally we go back the following year and run a more detailed weekend where people bring the material they have collected and get help with ID. Of course we also have our own material so they can have a go at tricky species.

It is a shame but we have not maintained a register of who has done our courses. This means that we don't have any measure of how well the traoining has impacted on contributions to the Recording Scheme. But there have been several very notable additions to the recorder effort. This is great because we have been trying to extend coverage into areas that are otherwise poorly recorded.

We are also in the process of developing a course that refines our 'Introduction to Diptera'. We have always felt there was something missing and so we are trying to assemble enough material to focus attention on the Brachycera - including Dolis and Empids, but starting with a key to families to make sure participants understand where the families fit in.

Do let me know if you are interested in running a course in your area.

Post field meeting reflections

This year's Autumn field meeting was far less productive than previous recent years. Unlike 2011, when we recorded over 200 species of fungus gnats, gnats were very scarce and we barely scraped past the 100 mark. Conversely, craneflies were a bit more abundant and we managed 58 species which is substantially up on recent years but still nowhere as good as lists for two decades ago. What has caused the change?

Forum members Andrew Halstead, John Bratton and Malcolm Smart

at Newborough Warren

The key point I think is that we visited many very suitable sites but the weather was much colder than in previous years. Many sites were west-facing and took most of the day to warm up, and by the time they were getting any sunshine the heat had gone out of the day. However, we cannot dismiss the effects of a very wet year which has had a detrimental impact on much of our insect fauna. Species that favour wet environments do seem to have fared better than in previous years, and Eristaline hoverflies have done comparatively well. There are slight indications that the recent downward trend in abundance of these species is being reversed, but we will really only know if the conditions persist and the fauna responds accordingly.

From a wider perspective it was extremely disappointing to see very few Heleomyzidae and Lauxanidae. Drosophilids were seemingly absent from many sites but we did manage six species of Platypezidae. All-told this was not the most inspiring of Autumn meetings but the company was good and our accommodation was pleasant. On this point I would happily recommend the Northwood Guest House in Rhos on Sea adjacent to Colwyn Bay and Llandudno. It was comfortable, our hosts David and Sandy were excellent, the breakfasts were excellent and we were made very welcome.

I am already planning 2013 meetings. At the moment we think it is time to explore Scotland in September, so a small group is likely to head north in early September. I will arrange a further four-day meeting in the south-east in October; as likely as not this will be based in Reigate, assuming we can make bookings.

My other remaining task is to sort out the venue for the Summer field meeting which I think will be in Lancaster. This is going to be a bit of an adventure because we will use self-catering accommodation at Lancaster University. This choice should bring the cost of the accommodation down to manageable levels for younger members so hopefully we will attract a new cohort of Dipterists from those who have attended recent courses.

Lunch at Newborough Warren - 

Malcolm Smart, Alan Stubbs (standing) Andrew Halstead and John Bratton.

Peter Chandler and Malcolm Smart taking advantage of a sunny spell after torrential rain.

Autumn Field Meeting - update

Today's weather was fantastic. One of those lovely autumn days with warm hazy sunshine. Where were the flies though?

We visited several very nice places but found remarkably few flies. That said, there were a few Platypezidae about and Peter Chandler took three species. Fungus gnats were very scarce, as were Heliomyzidae and Lauxaniidae. There were also very few hovers.

It looks as though the autumn is well and truly established in North Wales and that winter is rapidly setting in. That said, we are still only in early October but the water is jolly cold - I managed a partial dipping today bu losing my footing and falling into a muddy gully. I reckon I am at risk of becoming a liability!

Hoping for good weather tomorrow as we head off towards Colwyn Bay,