Spring data

April has passed and a considerable number of photographs have been taken, creating the biggest block of photographic data for this part of the year (Figure 1) that the HRS has assembled. Two points can be recognised. Firstly, the contribution of the UK Hoverflies Facebook group has been very significant. Secondly, that numbers of records derived from Flickr and iSpt etc have held up, despite the shift towards Facebook where several of the most active photographers now post their shots

Figure 1. Five-week running means of photographic records for the years 2011 to 2014, with the 2014 records represented as all records and a sub-set from sources other than Facebook (the situation that obtained before 2014).

The two trends offer a very positive indication of growth in hoverfly recording, which is very encouraging. It helps to show that the strategy that Stuart and I embarked upon five years ago is paying dividends. At the time, we were concerned that recruitment of new recorders was pretty low and that we were not connecting with people. That point represented a watershed between the traditional recording scheme and society-based approach to engagement, and more pro-active approach using 'virtual societies' where we set out to make contact by engaging locally. Our training programme has certainly had this effect and the internet has greatly expanded the basis for recording. Translating this into the full-spectrum recording that the old guard of the HRS have done may take a while longer, but even if only 5% of enthusiasts buy a microscope and start to look at preserved specimens we should replace the old guard with a new generation!

I think that the community of photographic recorders may also be extremely helpful in developing knowledge about yearly changes in phenology amongst more abundant and obvious species. This could be extremely interesting if developed as long time-series data. By way of example, two graphs are indicative - the first being a selection of spring species (Figure 2) and the second specifically Epistrophe eligans in 2014 (Figure 3).

Figure 2. Five week running means of combined photographic data 2011-2014 for a selection of spring hoverflies.

Figure 3. Numbers of photographic records of Epistrophe eligans in spring 2014 - data to 4 May and consequently incomplete.

The  data for spring species are combined for 2011-2014 and have been smoothed by a five week running mean. I will look in more detail at individual year data but everything is a bit skewed by larger numbers of records from 2014 and much more limited numbers in some years. I have simply posted the data for 2014 for Epistrophe eligans because in past years this species has not figured greatly in photos. The graph will be updated at some point because this species' flight season is not over. The trend is obvious though!

What flies do photographers focus on?

As interest grows in the possible uses of web-based recording, it crossed my mind that it would be worth looking at the data for flies. Until last year I did not maintain a log of hoverflies that could not be identified, so the dataset prior to mid-summer 2013 is only partial. I therefore selected the data for 2014 only, working on the principle that these data would offer a reasonably representative example of the situation between January and April. Obviously there will be much greater scope for evaluation at the end of the year, especially as there will be lots more species recorded during the summer.

Nevertheless, the data paint an interesting picture. They comprise all photographs where reliable locality data can be attributed. The only exception is that I do not extract records of tachinidae from iSpot because I know that Matt Smith (Tachinidae Recording Scheme) does this. However, I suspect this will make relatively little difference as the numbers of tachinids posted thus far have been quite small.

The graph (Figure 1) tells a facinating story. Firstly, it is clear that hoverflies make up the vast bulk of records. This year, the numbers are perhaps skewed by the development of the Facebook page (an additional 263 records over and above data from other sources), so I have excluded these records from the graph. The other families that attract attention are the bee-flies (Bombylius major dominates but there have been a few B. discolor), the Calliphoridae (bluebottles etc), what I will call 'Muscoidea' because this tends to be a dump for bristly jobs that I cannot readily place to family, and the Scathophagidae (dominated by Scathophaga stercoraria but with several Norellia spinipes). Other families figure quite lightly at the moment but I expect the Bibionidae to surge forward over the coming weeks.

Figure 1. Numbers of photographs of Diptera families logged for 2014 (1 January to 20 April 2014).

 

Why is there such a bias in the numbers? Well, clearly my focussing on hoverflies is a factor. I do not chase up shots of other flies that lack locality data, unless they are identifiable. So, there would otherwise be a bigger dataset. But, in reality, the Flickr groups and sets are not heavily dominated by non-Syrphid flies. Hoverflies are genuinely a major component of what is noticed and photographed. There are a few surprises, however; not least the frequency with which moth flies (Psychodidae) are depicted. I guess they are obliging and don't generally fly at the first provocation?

Now, having recognised and identified possible bias in the dataset, I wonder if there are other factors at work? I wonder whether there is an element of inbuilt bias because photographers start to know the flies that they or others are most able to put names to? Clearly this is not wholly the case because lots of shots of bluebottles and muscids are posted. Perhaps, therefore, the key is the frequency with which particular subject-matter is encountered, and whether it is willing to act as a model?

Is the picture that is emerging for Diptera the same for other Orders? Whilst I browse the web I get an impession that a similar sub-sample might be seen amongst the bees and wasps, amongst beetles and spiders and true bugs. I don't know whether higher levels of identification are possible amonst these groups? Somehow I doubt it? But, can it be quantified, and are there other recording scheme organisers who keep a similar log to the one I maintain. If such logs do not exist, perhaps there is a need to develop a co-ordinated approach to data extraction from the web. I think there are definite benefits to be had from internet recording, but there are also drawbacks. The question is, are there similar drawbacks for each insect Order, or are the limitations confined to certain Orders?

These issues are worth exploring further because there appears to be a dichotomy of views amongst recorders. Some are alert to the potential of internet recording, whilst others dismiss photography as a way of getting records. Clearly, those who dismiss photography have a good reson to be sceptical but it is well worth developing a much clearer picture of what can and cannot be done. Malcolm Smart and I have looked at the Asilidae (Malcolm is currently working though last year's photos). In an analysis of the Asilidae records I developed to 2012, he managed to identify the vast majority of shots (94%), generating at least one record of 20 species (74% of the family); but just six species formed 68% of the data.

I hope to develop further analyses over time, so that we have at least a basic understanding of the flies that are recorded by photography. It might take a little while, however!

Changes in recorder effort

The advent of digital photography and of web-based data capture techniques might suggest that biological recording is entering a new and vibrant phase. I'm sure it is, if one simply looks at the numbers of records that find their way onto databases. The big challenge is to establish whether these data actually reflect an increase in recording or a change in the ways in which plants and animals are recorded?

My interest in this stems from five years trawling through photographs on a wide variety of websites. I check between thirty and fifty sites each day, and during the summer months add between fifty and one hundred new records. I've posted some of the initial results in previous reports. My suspicion is that there will be considerable differences in the nature of recording, depending upon the ease with which animals and plants are both found and identified.

My instincts say that for those species that are easy to record there has been an increase in records. In the case of groups like macro-moths ,where moth traps have gained huge popularity, the volume of records may well have increased sharply. It would be interesting to see precisely what has happened. In the case of macro moths, perhaps there is an increasingly robust dataset? Moths are pretty docile and allow themselves to be photographed. Moreover, I suspect most can be identified from photos (I may well be wrong for a few genera).

Moving on to taxa where there is a need for specialist fieldcraft, and collecting specimens for microscopic identification, I suspect that what we are seeing is a shift in the robustness of the data. This was well demonstrated by Matt Smith and Chris Raper in their presentation of the Tachinid Recording Scheme at the last Dipterists Forum AGM. Chris and Matt showed that the data set was starting to change in composition as more photographic records were acquired. The most abundant species now include several that would be far less dominant if the data were strictly from what I would describe as taxonomist sources (i.e. people who actually study tachinids in a meaningful way).

The Hoverfly Recording Scheme has previously shown how the records of  more difficult genera are declining as a proportion of the dataset. This was apparent well before 2011 when we published the last atlas and continues to follow a similar downward trajectory (Figure 1). If anything, I suspect the rate of decline may be increasing. The big question then arises as to the cause. Is it simply that there are more records but no greater number of taxonomic recorders? Or, has there been a demographic shift?

Figure 1. Trend in the relative proportion of difficult species represented in the HRS dataset

To investigate this, I started to look at the composition of HRS recorders. We have previously noted that upwards of 50% of the data were supplied by just 21 recorders! The actual proportions bounce about quite a bit on a yearly basis so I looked at the contributions made by the top ten and top 20 recorders in any one year (Figure 2). This tells a fascinating story. All 20 recorders started to contribute between 1976 and 1992. In other words, the longest serving have been contributing for nearly 40 years and the youngest for 22 years! There were two big influxes, one in 1976/7 and a further recruitment in 1983-1985. Thus, the bulk of the major contributors to the scheme have been doing so for 30 years or more. Many on these recorders contribute between 500 and 1000 records per year, as shown in Figure 3 which depicts the contributions of the top 5 recorders. This figure shows how contributors data fluctuate quite substantially, reflecting rising and waning interest or the natural pressures of life.

Figure 2. Contributions to the HRS by the top 20 recorders over the period 1976-2013

Figure 3. Levels of data contributions by the top five contributors to the HRS. RM is 'Recorder 2'

If, however, one looks at the top 20 contributors each decade from 1976 to 2013 (i.e., 1976-1980; 1981-1990; 1991-2000; 2001 - 2010; and 2011 - 2013) the picture is very different (Figure 4). True, the same principle names are there, but the graph shows how major recorders only make a major contribution for a relatively short period of time. Critically, however, those recorders who started in the 1970's and 1980s have continued to form the nucleus of the Recording Scheme for much of the time. The data for the period 2011 to 2013 are misleading because there are several datasets that have not been updated since the call for records in 2009/10. Even so, the numbers of active new recorders are very encouraging and include at least 10 alumni of the training courses we have run in the past five years. This is most encouraging because the courses were intended to recruit replacements for the 1970s and 1980s cohorts and appears to be doing precisely that.

Figure 4. Contributions by recorders according to decade when they first became a major recorder.

The bigger question remains as to any changes in the types of data we are receiving. I think we can say with some confidence that the historic foundations of the scheme are slipping away. These were people who used Stubbs and Falk, and generally did all taxa. Many of the new recruits are equally well trained and also use Stubbs and Falk across all taxa. But, it seems likely that the absolute numbers of records entering the scheme has dropped in recent years because although new recorders have been recruited, the older ones who provided big blocks of data are less active. We can see this from Figure 5. It therefore seems highly likely that the composition of the dataset is changing, at least in the short-term. Its prognosis for the future is less clear, because we do seem to be recruiting good numbers of people who are versed in the skills needed to deal with difficult genera.

Figure 5. Numbers of records submitted to the HRS by conventional means, with the added contribution from photographs.

Getting to grips with hoverfly identification

Learning to identify any group of organisms is a challenge that at some stages can seem to be insurmountable. I'm not sure there is a 'right' or 'wrong' way as everybody learns in different ways. What works for some may not work for others; but there are some simple tips that may help.

• Identification is dependent upon recognition of features that are constant within the species concerned. In the case of hoverflies it needs to be borne in mind that they can be hugely variable in size and colouration in response to temperatures during larval and pupal development as well as sexual dimorphism and brood dimorphism. I know Alan Stubbs spends goodly periods of time checking a range of characters for consistent features when he develops keys - and the message that comes out is that relatively few are reliably the same.

• This complication means that whilst illustrations are useful, they only form part of the process. Understanding how to recognise the different Tribes and genera is crucial. This is where access to complete keys is very helpful - the keys will provide a series of markers that help to direct observations. It is also important to bear in mind that keys work on the process of elimination; so, the earlier they appear in the key the more genera or species may have this feature in common. In addition, once two different pathways are followed, it is quite possible that a very similar character may be used to identify two very different species. Understanding these relationships is important. This is one critical reason why we have been resistant to producing a guide to all hovers without detailed keys. The current WILDGuide is a best effort to introduce the family but cannot be regarded as perfect. The 'key' to tribes is critical and really should be used in the first instance; at least until you have seen most of them or recognise obvious ones. If in doubt, go back to first principles.

• Working with keys does not mean that one should not use the photographs/illustrations to help arrive at a conclusion, but the crucial point is not to force the identity to fit the picture. There are several obvious areas where this can (and does happen): hive-bee mimics and bumblebee mimics often cause problems. It is important to recognise that whilst the markings on the abdomens of hoverflies often appear to be distinct, they are frequently no guide to the species. Confusion within Syrphus is an obvious example where the critical characters are microscopic. And, I have regularly been asked 'so why is this a Syrphus' - answer - you need to examine the upper surface of the squamae to be sure - but these are not visible on photographs or on specimens with the wings folded.

• If one sets aside the keys and simply tries to match specimens to photographs there will always be challenges because the introductory guides cannot ever provide all the necessary corroborative information (bear in mind that Stubbs & Falk is well over 500 pages of keys and descriptive text plus illustrations of male terminalia). It may not always be possible to reach a firm conclusion for a substantial sub-sample without taking specimens and keying through using a microscope and detailed monographs. So, we must work with what we have to hand, and use a certain level of judgment. Corroborating evidence can be helpful but is not foolproof - e.g., time of year, location, habitat, size (difficult to be sure with photos). It is distressing but not surprising that the NBN often has maps with dots well out of range - those recorders ought to have challenged their own IDs if they had read the distribution information.

• We have tried to illustrate critical features in the WILDGuide, and where these are shown they should help to separate species involved. This is not perfect, however, and making judgments is often dependent upon experience. So, the novice should not be disappointed by problems in making early identifications: until you have a mental picture of critical features the process will always be slow and frustrating. But, it does get easier.

• In my experience the majority of 'novices' actually come across quite a limited range of species. Most are 'common': Eristalis, Syrphus, Helophilus, Volucella form the majority of the assemblage. Tricky genera such as Cheilosia, Pipiza and Platycheirus are rarely seen over and above some very obvious animals such as C. illustrata, C. variabilis and P. albimanus. Recognising the genera is a good first base. Once you can readily say that this is an x or y, then you can move on to separate the species.

• One way of getting to know what the animals themselves look like is to make a habit of working through the guide and reading descriptions and species accounts so that you have a feel for range and variation. As a small boy I spent hours engrossed in whichever book caught my attention. I had a pretty good idea what I was looking for even without seeing the animals themselves. What is more, I knew what to look for! So, as an example, I recall reading about puss moth eggs and that they were found in pairs on the underside of poplar leaves. At the right time of year I looked for the eggs and the second leaf I turned over yielded a pair of beautiful little eggs - I was hooked! I shared this haul with my pal John Stevens - each of us rearing a wonderful caterpillar and enjoyed watching them make their cocoon. A beautiful fluffy white moth emerged the following year!

• Identification is a process of elimination. It is as important to understand what the subject matter is not, as much as what it is. So, one can say - I know with confidence that this is not an x or y - and hence the numbers of possibilities is reduced to those that actually fit the what it might be section. The critical markers generated by previous experience are part of this process. Remember: getting identifications right first time does not necessarily mean you have learned anything - you learn as much from getting it wrong and of course when this happens you actually have a mental hook to use to help in future. I use this process all the time. I cannot remember everything, but if I come across certain cues, I am reminded of past mistakes (we all make them).

• Those entomologists who maintain a collection have the advantage of referring back to voucher specimens, but you can do something similar with photos - creating albums in taxonomic order. These may help - although you might also usefully look at Steve Falk's excellent Flickr library.

Following these processes, I think the best way is to think in the following manner:

1. Can we establish the Tribe to which the specimen belongs?

2. If so, aim to the relevant part of the book. In many tribes the animals are very different, and so you may find that there are several very similar animals involved.

3. For many of the Tribes, a simple key to genera is provided - follow this and you should get to the genus.

4. When at the generic level, individual photos should help, but there are also supplementary photos that should help - use these where they are available.

5. If you come to a conclusion about a species, check the descriptive information and note whether there are similar species. If similar species are listed, check against these before making a judgment.

6. If working from a photo - post it on a suitable platform (UK Hoverflies Facebook group, iSpot, Wild About Britain) and see what others think.

7. Don't be put off by mistakes - simply look upon them as a learning experience and have another go with other examples. Remember, we all start at the beginning and progress; and even the 'experts' make mistakes!

Validating records and the issue of killing invertebrates

The question of whether or not it is acceptable to kill insects in the process of biological recording is one that polarises views. On the one hand there are some who believe that all records should be backed up by a pinned specimen; on the other there are those who believe that nothing should be killed. Some people argue that insects deaths resulting from impacts with cars is accidental and therefore acceptable; others argue that roadkill contributes to the overall loss of biodiversity and should be minimised as far as possible. I fall somewhere in the middle of these views. It therefore seems to me that there is merit in exploring the various issues in a bit more detail.

To start with, it is worth thinking about what biological records are used for, and why so much time, effort and money has been invested in such initiatives as the National Biodiversity Network, the Biological Records Centre at Wallingford and the plethora of local records centres and recording initiatives. Not to mention the armies of volunteers who undertake everything from the hugely important Wetland Bird Surveys and Butterfly Monitoring schemes, to national recording schemes, atlas projects and bioblitzes.

Robust, reliable and up-to-date information is an essential part of nature conservation. It underpins the site designations that protect International, national and local wildlife sites. The trends that can be discerned inform the development of red lists and protected species legislation. And, of course, trends also influence political thinking. If the underpinning data are poor, the subsequent analysis will be weak and vulnerable to attack from those whose interests are threatened by changing legislation and policy; be that development of marginal land or application of a new form of pesticide. So, there is an onus on those who compile the data to make them as robust as possible. In the case of the Hoverfly Recording Scheme, the buck stops with Stuart Ball and with me. As I tend to do the taxonomic validation of records, I thought I would set out my thoughts on the issue and explain how  go about making sure the data are as robust as realistically possible.

The one reliable way to be absolutely sure is to only accept records generated by oneself or specimens verified oneself. Such an approach is impractical, but I am aware of recording scheme organisers who have taken such a view. Following the latter course means that the dataset is extremely sparse and probably not sufficiently robust to make statements about the status of species, either geographically or in terms of abundance and responses to change. This approach is not viable for the HRS and therefore we must accept that a small proportion of the data we absorb are incorrectly identified. As I won't claim to be perfect myself I think I must simply do my best to establish sufficient rigour to give confidence in the dataset (the man who thinks he does not make mistakes is either arrogant or too fastidious to be effective), I therefore use various tests to see whether the submitted data are accurate.

When we accept records from recorders, we can make an assessment of their approach, based on the composition of the list that is submitted. There are obvious clues. For example, there is a well-known insect ID guidebook that has a very glaring hoverfly identification error in it. When I see records of that species in the dataset an alarm bell rings and although we absorb the records into the database they are flagged as questionable ID - which means the records are never used in analysis. I hope that error remains in subsequent editions as it is a fantastic marker for one line of recording! It also means that I have a knowledge of the recorder and can be vigilant for future records. These data also show how incomplete guidebooks can have a potentially damaging impact on datasets.

The second clue is whether difficult taxa are included in the list, and which parts of those assemblages (e.g. Cheilosia, Sphaerophoria etc) - when I see the gender of certain species included in the data I know the data has been submitted by somebody who matches specimens to pictures and does not read and respond to the text. The chances are, therefore, that they have not used the keys and therefore there can be no certainty about the validity of the records. Here I flag the easy species as accepted and flag the others as questionable. In this case, the lesson is that even if people have the right text books, a proportion will not use them properly and will not match the standards that the recording scheme organiser has to adhere to.

The third clue is whether or not there has been validation - either a voucher specimen or a photo. If a voucher specimen  is available,I start to feel that the recorder is making an attempt to use the very necessary processes of cross-checking that are needed to deliver reliable data. As long as there is nothing in the really difficult taxa, then I may well accept the full dataset. I might want to see specimens/photos for difficult taxa i.e. those we would class difficulty grades 4 & 5 in our system of validation (1 = generally safe to accept, 4-5 represent taxa that require very diligent validation). Once I have seen specimens and have a feel for the competence of the recorder I am more likely to accept their records immediately. That is, assuming their IDs are correct. Sometimes I get photos to support records and find that the genus is wrong and sometimes even the family!

Now, moving on to the value of this process. It means that the majority of records do get accepted, but that the dataset is heavily skewed towards commoner and more readily identifiable species. This presents us with a problem because the scheme has a very strong link to nature conservation. For example, we use its data to evaluate the conservation status of hoverflies (which is listed in our book). We can only do this by having access to data covering the full range of taxa - a sub-set will not be as valuable to conservation and it could mean that an immensely useful conservation tool is blunted. That would be a real problem I think.

In addition, datasets that do not include all taxa also skew the robustness of their use in trend analysis and its application to developing environmental and policy issues. Complexity of identification is not a valid analogue for relative abundance. Some very common species of hoverflies are fiendishly difficult to identify without strong magnification and examination of characters such as the male terminalia. For example, as a general rule, the genus Sphaerophoria cannot be identified beyond generic level without detailed examination and reference to comparative material.

So, I believe the case is well-made for rigorous identification and validation processes to make sure that whatever data are available are reliable. I think we can be reasonably assured that the majority of the HRS data meet this criterion, but we can never be 100% certain. Whatever the actual situation is, I feel I can say that the data are screened to the best level that can be achieved with the resources we have available to us (i.e. unfunded and using  experience of more than 70 years).

Moving on to the issue of road kill. There are two aspects to this. One is that, if a car is used to make visits to the countryside, it is almost certain that the drive to and from the site will involve the death of a number of invertebrates. The numbers today are doubtless much lower than they were 30 years ago, but they cannot be dismissed as irrelevant. Consequently, it is possible to compare the careful selection of a sample of specimens with the indiscriminate impacts of driving the car. Both lead to the death of a number of invertebrates.

The collection of specimens is a very deliberate decision to capture and kill animals. As such it can be judged because the decision has been made to kill; it is not an incidental result of a more legitimate process that can be justified for personal reasons - or is it?

In the case of animals killed by cars the question arises as to whether these deaths are accidental by-products of a legitimate activity. Those advocates who argue that they  are not deliberately killed overlook the fact that a clear decision has been made to drive the car. Making that decision means that we also make the decision to knowingly kill insects (everybody has experienced the thud of an insect hitting the windscreen, followed by the trail of ooze that paints the screen with the animal's remains).

An example that ought to resonate with readers is the problem of recording bumblebees. I stopped recording bumblebees a long while ago because I cannot do them without killing them. But, we might all help if we picked up these roadkill and submit them to a scheme (I have long held that walking roadsides and collecting bumblees killed by cars might be a good way of looking at the effects of roads on bumblebee populations). The point of course is that without valid data, bumblebee conservation will lack the critical tool to influence policy and raise the profile of bumblebee conservation.

Looking at these two scenarios, it seems to me that it is not possible to make a value judgment about the acceptability of killing specimens without also asking whether it is acceptable to drive a known killing machine and regard the deaths of countless insects as an acceptable legitimate by-product. If specimens are killed and the data that result are used for a valid purpose, including wildlife conservation, it is surely no worse than driving your car to go to work, for a country visit or to shop in the out of town hypermarket? And, it should also be remembered that the lorry that delivers food to the shop will also have killed insects.

It therefore seems to me that we cannot really absolve ourselves from the processes that kill insects. There is a paradox that involves value judgments about the differences between the two activities. Cars lead to betterment of our minds, bodies and happiness above whereas the production of the highest quality evidence that MIGHT be useful in changing land management policies.

There are two ways of addressing this issue. Firstly, if convinced that there is a need for taxonomically rigorous data, we can make appropriate collections of invertebrates with the expressed intentions of contributing rigorously assembled data to a scheme that does set out to help influence policy. Those who remain uncomfortable with deliberate killing of insects can still do their best to provide details of what they see, at a level of validation that is consistent with their value judgments. There is no compunction to take specimens, especially as for most people the primary objective of a countryside visit is a nice day out and improvement of the mind and body. I would argue that everybody, however, has a responsibility to make sure that the indiscriminate deaths of insects are minimised or or are ameliorated by improving the body of information that might help to save wildlife.

I would therefore argue that where the car is used to visit the countryside, one should also participate in whichever recording schemes fit our interests in the natural environment. It might be as a birder - if so, perhaps contributing to WeBs counts, breeding bird surveys or other initiatives. If so, added value might be the incidental (accurate) records of other taxa observed in the course of the day out. Alternatively, it might be conducting butterfly transects and noting the occasional beetle, hoverfly etc. Or, it might be compiling a comprehensive photographic record of the insects visiting a particular site. Critically, unwillingness to kill animals indicates a love for the natural world, and what better way to love it than to make a contribution to the science that might help to conserve it!

So, with that I will sign off by emphasising that everybody can make a valid contribution to conservation by making their trips into the natural world count for as much as possible. If datasets are strong, then the evidence placed before politicians becomes more powerful. That in turn gives the natural world a fighting chance, providing it has technically competent advocates who can present a compelling and evidence-based argument. We therefore need the taxonomically rigorous recorder as much as we do those who prefer to avoid collecting.

The natural world is there to be valued. It enriches lives and is the life-support system for the planet. Our responsibility is to therefore to protect it, and to provide it with the defence mechanisms it needs to survive the ravages of man's worst excesses.