Cheilosia caerulescens

I have watched my mother's patch of house leeks for several years now, hoping to detect Cheilosia caerulescens. on one occasion I found a single mine, but no real evidence that the fly was here. Today there was a big change. The patch looked very sorry for itself as can be seen in the accompanying photos.

This is a species that was introduced by the horticultural trade, probably about ten years ago. It is now on the march, probably augmented by additional imports. We know it from the London area (quite common) and from south-east England into Bedfordshire and as far east as Norwich. It seems to be recorded more frequently by photographers than specialist Dipterists and is therefore highly suited to recording by 'citizen science'. If you have a patch of house leeks then take a look, photograph them if there are signs of damage, and put these on iSpot or the Hoverfly Recording Scheme site (or UK Hoverflies Facebook page).

I tried providing links to two very nice shots of the hoverfly on Flickr but unfortunately Blogger could not locate them (they work for me).

Is the biological recording community ageing?

When I started in entomology some 40 years ago I attended the meetings of the entomology section of the Croydon Natural History Society. The section was chaired by Ken Evans who was a great inspiration and very kindly provided transport to several of us younger entomologists to moth trapping venues. At that time there were respectable numbers of young members of the section – apart from 'yours truly' there was Graham Collins, Mike and James Halsey, David Lees, with a slightly older generation comprising the likes of Jim Porter and Roger Hawkins. Several of that group have gone on to be quite influential in today's entomological World. I am told that the section is still running but that there are no new recruits – it is getting older and its numbers are diminishing.

Similar declines in attendance and membership are reported by other societies and there is a perception at least that the numbers of up-and-coming entomologists are declining. Is this really the case? Somehow I doubt it.

A common view is that as Universities no longer teach taxonomy, these skills are being lost. But is this really true either? I look back to my taxonomy-dominated undergraduate days – both at A-level and in my first and second years at Uni and wonder whether my interest/involvement in invertebrates was strictly generated by that experience? I certainly moved towards an interest in moths as a result of one field course, but I don't think the teaching element necessarily prepared me for any work involving insect taxonomy and in particularly Diptera.

It would be fair to say that the course was responsible for basic analytical skills and probably the 'confidence' to try keys. After that I was on my own and dependent upon interactions with others more skilled than me. For that I relied upon membership of various societies and meeting and discussing with both my peers and the then luminaries of those bodies. To my mind, the opportunity to engage with people with more experience than me was of particular importance.

Fast forward to 2015. Relatively few young people attend society meetings and the general view is that the next generation just is not out there. I think this is a misconception because those such as me are long in the tooth and still rely on personal contact. We even enjoy meeting people and attending field meetings, AGMs and other events that bring together like-minded individuals. Our successors work in a different paradigm – that of the electronic media. Various Facebook forums are populated by a wide range of age classes and although one gets the feeling that a substantial proportion of contributors to the UK Hoverflies page are not in the first phase of youth there iare numerous of young entomologists.

The big question that follows is whether that new generation will be willing to take on the sorts of roles that have traditionally maintained a community of special interests such as hoverflies etc? My guess is that they will, but that depends upon the ways in which the older generation recognises and adapts to a changing World. It is we that must think in new ways, otherwise the structures that we cherish will fade away. BUT, I think there remains a place for the traditional society and for the contributions that they make to field biology.

If one simply looks at interactive media as a way of immediately satisfying needs for assistance with identification or sharing the excitement of a recent find, then the traditional society will become redundant. That is only part of the story, however.

Many of the most important initiatives and activities have resulted from these societies. For example, there would be no Hoverfly Recording Scheme as we know it today without the BENHS, who sought out the grant that allowed the first edition of Stubbs and Falk to be published (for that matter, there would not be the Wildguide either because we would not have taken up the HRS). Major taxonomic works at affordable prices is something that societies can make possible. The alternative is the Fauna Ent. Scand. series, where the publications are so expensive they can only be afforded by a few specialists. Yes there will be popular books such as Britain's Hoverflies but the chances of another Stubbs & Falk would be very remote because sales are not high and profits will be marginal.

Of course one could argue that the future of publication lies in electronic media. That may be true – I am too long in the tooth to envisage a World without books but it may be on its way (sadly). Even so, books don't just happen – they need the authors but they also need peer-review, editing, formatting and publishing – tasks that demand a range of skills. So, there remains the need to create a forum that is capable of bringing together those disparate skills. Such a forum is analagous to a Society, so in all respects there remains a need for Societies. There is therefore a place for young people to join societies and to get involved.

The question then must be 'why is society membership ageing?' Perhaps part of the problem is that electronic media have left the traditional society behind and it is time for societies to re-invent themselves in an electronic age. On-line resources are an obvious way forward, but providing those resources is actually not without costs. Hosting websites is not expensive but it does require funds and it also requires continuity – not just altruism on the part of a benevolant individual. There will be other costs if communally beneficial projects are to be initiated and maintained. If the communty relies on individual altruism the situation will arise when a major supporter dies and the society dies with them. So, it might be argued that there remains a need for formal societies to provide the necessary platform for interaction.

Thus, it seems to me that there is a two-way process to be pursued. On the one hand the old guard must embrace new technology and the communication medium that it provides. Meanwhile, the next generation must engage and join societies to make sure that the platforms for engagement are maintained. Those of us who currently deliver particular roles are simply the custodians of an ongoing legacy. We must support and enthuse a further generation, whilst they in turn must rise to the challenge and take on the mantle as the old guard gives ground and makes way for new blood.

This paradigm is one that all recording scheme organisers need to consider too. They (we) do not own the schemes; rather we are custodians and guardians who need to foster a new generation and make sure that our successors are well established before we have to give up. This seems to me to be the next big challenge for the Hoverfly Recording Scheme. Stuart and I have run it for nearly 25 years. We have plenty of energy to go on, but there is a danger that we will kill the scheme by staying in place for too long and not giving space for a new generation to become established. It is a dilemma that we are starting to consider.

Our training programme was the first step in that direction – growing the constituency and the capacity. The Facebook page is arguably a second stage in which a wider constituency has been built and potential replacements have started to show themselves. The next stage must be to expand the team, spread the load and make sure there is a new cohort of 'names and faces'; after which we must subside into the background and let others run the scheme along the lines that they see fit.

So maybe the critical slogan is: The society is dead. Long live the society!

Developing a network of parataxonomists

The concept of parataxonomy is not new – in his work in Costa Rica Dan Janzen became a major exponent of the idea, which has caught on in many ways. Current crowd-sourced identification systems such as iSpot are arguably one form of parataxonomy. I like to think that the UK Hoverflies Facebook page has parallels with parataxonomy – especially where there is a fusion between people whose primary interest is photography and those with interests in biological recording.

What I find especially encoraging is the way in which this interaction is leading to more active members searching out species that they might hitherto have ignored or not seen. From a first glance, I think the data from 2015 will be rather different when compared to that from 2014. There seem to be many more posts of Cheilosia, pipizines and the 'awkward squad' of small Chrysogastrines and Bacchines.

It is also noticeable that several people whose initial interest in photography has progressed to retaining specimens to pass on to me for identification; thus we will hopefully be able to match photos to firm identifications. In time this may help to refine our understanding of how to identify species from photos and the subtle features of live animals that are lost in museum specimens. There is a long way to go, but this is a great start. Ideally we need to recruit more participants in this approach.

Thinking in broader terms, it strikes me that there are potentially significant numbers of people who want to develop inventories of what occurs on their favoured site or locale – maybe an island, a village or parish. Obviously photography will help, but it can only go so far.

I'm far from clear how many recording schemes actually engage with photographers – probably relatively few to any major degree. Some will doubtless feel that there is no point engaging to find that most species cannot be fully identified (I have head that from several scheme organisers). Others may feel they cannot commit the time, which is a fair point because this sort of engagement is highly time-consuming. Yet, if we really want to develop a strong network of recorders of more difficult taxa we must engage and look for ways to increase interaction between interested and willing local recorders and those with the taxonomic skills needed to create reliable records.

The development of a more comprehensive parataxonomic network therefore seems to me to be an essential next step. We need to find a way of encouraging/recruiting people who will collect specimens and pass them on for identification (or storage for later identification), and to match this commitment to the available taxonomic specialists. Most recording scheme organisers probably do this in an ad-hoc manner when they identify problem specimens sent to them. But, we might do so much more to develop a data flow that really improves coverage. Parts of the country may not be populated by specialists in more difficult taxa, but there is a better chance of finding people who might collect material for dispersal to specialists for identification.

Making such a system happen is a challenge. Inevitably, if one starts to collect specimens there will be a stage when new recruits only see and retain obvious species, but they will (and do) develop skills that yield a wider range of taxa. What is important is to make sure that material submitted gets identified and logged, with feedback to local contributors so they know what they have generated and can start to see a picture of their chosen area unfold.

I would love to get such a system up and running for hoverflies but am mindful that all sorts of other flies will be passed on and will need identification. I therefore think that we might try to make something happen amongst the schemes run under the umbrella of Dipterists Forum. Is there somebody that might take on the organising role if we could make it happen? I'm not sure I have the time, but will happily promote such a concept amongst the developing networks of UK Hoverflies and UK Diptera Facebook pages.

The follow-up question is then whether there is an appetite for such a system developed through the NBN and local records centres? My vision would be the development of a national network that would generate records from widely dispersed and otherwise under-recorded places. If successful it might help to resolve the problem of some areas of the UK being substantially under-recorded.

Now, this all sounds fine, but the follow-up question is whether there is the technical capacity to identify the inflow of specimens? At current levels of activity there probably is. BUT, we have seen with the UK Hoverflies Facebook page that its success means that there is a need for several toxonomically competent people to engage. In the case of UK Hoverflies we now have a team of five running the site. I could not have coped without the help of Ian, Joan, Judy & Stephen. I am eternally grateful to them all for their help, and also to Gerard Pennards upon whom we call for expert advice fairly regularly.

That experience clearly illustrates the need to think in advance about the scale of uptake that might be involved and what it means in terms of organisational and technical support. Running a recording scheme today is very different to the concept developed in the 1960s and 70s. We need to embrace the new technology but also to pay attention to the technical capacity needed to make such systems work.

This seems to me to be the next stage in the biological recording journey and one that should be considered by those who have an interest in promoting biological recording.

Hoverflies in April

As we pass into May 2015 the weather has followed a bit of a modern pattern: a warm sunny April followed by a cold snap in early May, just when the insects are getting going. Hopefully the change will not extend over a long period but we do need some rain!

As part of my ongoing efforts to provide feedback to contributors I produced a set of graphs this morning for the UK Hoverflies Facebook group. They tell quite an interesting story for developing hoverfly activity in April. Real activity seems to have started a few days earlier than 2014 and to have continued to gain pace for much of the month (Figure 1). This contrasts with 2014 where there was a bit of a dip mid-month. In both years, however, there was a strong dip towards the end on the month.

Figure 1. Centred 3-day running means for the number of hoverfly records from photographs in April 2014 and 2015.

Analysis of the composition of the lists created shows how a relatively small number of species dominate the data (nearly 1600 records in 2015). Six species make up 63.5% of the records and 90.2% of the records are derived from just 20 species. The six most abundant species recorded were (in Alphabetic order): Epistrophe eligans, Eristalis pertinax, Eupeodes luniger, Melanostoma scalare, Platycheirus albimanus and Syrphus torvus. Details of the overall species list can be seen in Figure 2.

Figure 2. log2 representation of records of hoverflies recorded from photographs in 2015. Species represented by single records are not represented by a column owing to the use of log2

As in previous analyses, it can be seen that the dataset is dominated by a small number of species but that the overall list is substantial with large numbers of species represented by occasional records (Figure 3). This situation is primarily a function of the recording technique. My active field sampling highlights much wider species representation and far more species within genera such as Cheilosia and Pipiza.

Figure 3. The relative abundance of species within the photographic dataset for hoverflies in April 2015: over 60% of the species are represented by 9 or fewer records.

In addition to maintaining a log of firm identifications (or as near firm as possible), I have maintained a log of partially identified photographs (502 records). This log indicates that around 23% of photographs posted cannot be reliably identified. It is a rate that is not inconsistent with previous analysis (see http://www.bacoastal.co.uk/Entomology/2015-Photo-report.pdf). The rate at which partial records accumulates differs little from the main dataset, but does fluctuate (Figure 4), partially depending upon the popularity of photographing the genus Syrphus (Figure 5).

Figure 4. absolute numbers of records of photographs that cannot be identified to species with a 3-day centred running mean super-imposed.

Figure 5. Total numbers of representatives within Tribes (red) with numbers of individual genera (blue) reported at log2 scale. Single records are not represented on the scale, hence some gaps.

These fairly simple analyses help to show the potential power of photographic records in some aspects of invertebrate monitoring. The development of a network of photographers is therefore a definite enhancement of data collection and has the potential to help to provide a real-time impression of how invertebrates are responding to seasonal fluctuations. Problems with identification remain an issue, however, and it is therefore important to think about the ways in which photographic recording can be used to maximum effect, without compromising the continuing need for data collected by traditional methods.

Biological recording - an issue of administration

In recent years there have been several initiatives to improve levels of biological recording. The most prominent was the establishment of the NBN Gateway as well as that of iSpot and the OPAL project that gave grant-aid to improve skills and data flow. In the case of the Hoverfly Recording Scheme, we were greatly helped by grants to buy a projection microscope and 13 teaching microscopes, and to produce teaching literature. We also benefited from a grant from Natural England to buy a computer and projector. In the case of the HRS this grant-aid has been put to good use and we have run well in excess of 50 courses and engaged with over 400 prospective recorders. It has been achieved through the activity of two recording scheme organisers but has depended upon a network of local organisers.

The results are difficult to correlate with increased recorder effort, but in four areas there have been very tangible benefits: Devon, Glasgow, Norfolk and Northamptonshire. In these places there has been a definite upsurge in effort. Why should this be? The answer is simple: in addition to our provision of teaching, there were local people whose interests have meant that they have become leaders - the very necessary glue that holds a group together and makes things happen.

Over the same time, there have been a number of further innovations. Social networking media have become more universally accepted, even by an older generation, and on-line data entry has become more practical. Some recording schemes and organisations have their own systems (e.g. Bird Track) but there is also iRecord. These relatively simple systems (not necessarily in programming technology) encourage data submission by some people. Indeed, Bird Track has even persuaded me to monitor my local ponds and to regularly enter data on their inhabitants.

Superficially at least, biological recording is making considerable headway. Basic metrics concerning the numbers of records submitted or numbers of contributors are powerful political allies that show how biological recording is an active expression of 'the Big Society' at work. In terms of the HRS, the biggest metrics are headline figures about a significant rise in the numbers of records submitted in 2014 - the highest ever and about 30% more than the long-term average.

Beneath the headline figures, there are issues that are very often overlooked and might fall into the 'I do not recognise' bracket if placed before politicians and some senior management. After all, increasing biological recording is simply a question of getting more people out and about, and getting the Recording Schemes to engage with them to verify records. Is that so? In reality, I hear from recorders who complain about lack of verification of their records on iRecord, who find the Record Cleaner responses frustrating and who are amazed to find that their records have not passed between the Local Records Centre and the NBN (at this point I should say that the HRS and DF are working to place updates of data on the NBN).

These various gripes draw attention to the big issue in biological recording that has yet to be recognised or addressed. Records do not simply magic their way from a recorder to the NBN, Recording Scheme or Local Records Centre. There is a very necessary administrative structure; some paid, some voluntary. The professional element can be quantified - staffing costs, staff time, office costs etc. The voluntary organisational component is less obvious but is equally important. It too draws on staff time but because it is voluntary the costs and implications of increasing effort are not obvious. Cutting the professional component will not necessarily mean that the voluntary component will either take over or carry on as normal.

One of the biggest issues I have always felt was: if there is to be a push for more biological recording, where is the taxonomic expertise coming from? Who is going to do the local motivation and organisation? And, why are they going to do it? True, some will get involved because they see biological recording as an essential part of cataloging and conserving wildlife. But, this begs an important question: if you are interested in a particular specialist group of organisms, is your interest in the organisms or in the organisation needed to record them?

These questions highlight a developing issue. Although one can fairly rapidly lay out the base of a pyramid, it takes years to develop the superstructure. True, modern data management systems may help to resolve simple issues and some technical issues such as incorrect grid references, but there is still a need for a human being to take decisions and to provide technical input. Web-based systems such as iRecord and Bird Track need a direct human interface to verify the data and to provide some interpretation. Bird Track is a BTO initiative - the BTO benefits from a professional superstructure, part funded by membership, partly by consultancy services and partly by statutory agency/government funding. iRecord is linked to the Biological Records Centre at the Centre for Ecology & Hydrology. Again, funded and staffed with a professional community.

In the case of iRecord, I understand that verification of data is largely undertaken by volunteers - Recording Scheme organisers or local specialists. This verification process is largely dependent upon whether a scheme organiser is willing to undertake the task. Some have signed up to the role; others have not. Feedback from some users expresses frustration that their records have not been verified: in other words there is a willingness to submit records but there is a lack of capacity to verify the records. I certainly know of Recording Scheme organisers who would be very unwilling to verify records based on photos, or from people who are unknown quantities.

Verification is a complex process and is dependent upon trust - big blocks of data from established and reliable recorders are relatively easy to deal with. Small blocks of data from unknown quantities and from relative novices are more intimidating. The role of a Recording Scheme organiser is varied: data verification is part of the job, but then so is motivating recorders, answering queries, checking specimens and, perhaps most importantly providing feedback. Schemes that act as a black hole are rarely very dynamic and don't attract interest from any but the most committed.

Recording Scheme organisers are therefore an essential public interface. In many cases they were recruited (or set up schemes) before crowd-sourced data and 24-hour contact. In essence they were interested in the organisms concerned and focussed their energy on gathering data that improved knowledge about the animals or plants concerned. Some will have been working towards the production of an atlas or revisions of keys. Few would have anticipated the modern role of teacher, motivator, data handler and media manager. Some have adapted, whilst others have not. Most importantly, the question arises: who is going to replace the current cohort?

This is arguably the next big question to be resolved. It is all very well growing the numbers of records, but there is a danger that in developing a huge biological recording effort, the strains placed on the organisation superstructure will be such that nobody will be available to carry through a smooth transition from one generation to the next. Growing a new generation of 'administrators' is therefore essential.

This morning, it struck me that the HRS had grown substantially in terms of administrators - it is no longer just me and Stuart Ball. The UK Hoverflies Facebook page could not function without three additional technically competent members who regularly engage to help with identifications. Also, the site was set up by another member who is far more competent than me in these things. Two people are now administrators of the site together with three of the four technical specialists. All of a sudden, the vast rise in hoverfly recording activity is put into perspective - running the scheme is not down to Stuart and me, but involves the combined contributions of seven people. Likewise, the increased activity in Devon, Glasgow, Norfolk and Northamptonshire reflects the presence of local leadership structures.

Leadership at all levels is surely the issue that has to be resolved if biological recording is to fulfill the aspirations of conservation agencies, NGOs and Government? Some bigger societies have possibly got this in place already. BSBI arguably has a network of local recorders that cannot be matched by many other taxonomic groupings apart from birds and mammals. There was an initiative to improve moth recording, but I believe that funding for this has either diminished or ceased. Dragonfly recording is doubtless much better structured than recording of other taxa. In reality, recording of many more challenging taxa will always be dependent on a small number of people both in administration and in field work.

Growing these elements is therefore a matter not only of growing grass roots interest, it must be accompanied by growing the administrative superstructure that is essential if recorders are to feel valued and that somebody is taking an interest in their contributions. Without this input, there is a real danger that grass roots expectations will be frustrated and there will be finite limits to what can be done. A rise in the numbers of records and in recorder numbers should therefore be seen as a positive first step but the job is not over - it has just begun. The next step is to develop the a wider network of shakers and movers: that is a much slower process.

A need for a long-term photographic archive

The quality of modern digital photography is amazing. One has only to turn to Flickr wildlife pools to see a fantastic array of shots. Obviously a good many are of regularly photographed subjects but amongst them there are absolute gems. In the case of hoverflies, I have spent the last 6 years investigating photographic records and have built up a substantial database of URLS that effectively form records. Some of these shots will be available for the foreseeable future but if they reside on Flickr Pro their future is less certain because they will not be hosted when the photographer stops paying for the web hosting facility.

This raises the tricky question of what happens to photos after one's inevitable demise? A collection of insects can be donated to a museum (well, maybe a few can), but what about one's photographic archive? In the case of insect photos, we might well want such an archive and retrieval service. Steve Falk's Flickr pages are an invaluable identification aid and his photos have been immensely important in the Hoverfly WILDGuide. So too has the work of several other excellent photographers. I would be very sad if these fantastic resources were not 'saved for the nation'. After all, in many cases they are not only fantastic wildlife shots but also works of art.

It seems to me that there is a need to tackle the question of a national photo archive - is it not time that one was created? Preserving photos for posterity also provides a way of storing photographic vouchers and also establishes a huge educational resource. It seems to me that there is a need for the biological recording community to look at this issue and to consider the establishment of such an archive. It is a pretty novel scenario, so I imagine it could be put together as an HLF bid as a follow-up to other 'citizen science' initiatives.

I suspect that archive facilities would attract huge support from photographers. In many cases there will be photos that might be identified in the future, so this could be a form of record storage in the same way that museums store large volumes of unidentified material that may at some stage help to answer a critical question. Who should be encouraged to pick up the baton and provide a lead?

Insect collection - a philosophical question

Comments on a recent post in the UK Hoverflies Facebook page raise some important questions about the practice of retaining specimens. I hope the following will help to set some perspective.

The dataset held by the HRS comprises a mixture of field observations and preserved specimens. There would be very few records prior to 1976 without the collections of long-dead entomologists. Indeed, this is true for most datasets involving invertebrates. The one problem with museum collections is that they tend to be dominated (proportionally) by 'scarcer' species and by species that are tricky to identify. This creates an unhelpful imbalance that means that pre-1976 data are not ideal in presenting an image of what the hoverfly fauna looked like in the past. The one thing we do know is that certain species were regarded as 'prizes' (e.g. Volucella zonaria). Some data from this period are definitely helpful in reconstructing our knowledge of particular species. Anybody wanting to see this in action should look at two papers Stuart and I published on Volucella inanis and V. zonaria.

http://www.bacoastal.co.uk/Entomology/2004-Volucella-zonaria.pdf

http://www.bacoastal.co.uk/Entomology/2003-Volucella-inanis.pdf

Many of the species that were most prized were big and bold (e.g. Callicera aurata). It is now possible to read the accounts of field trips by one of the early Dipterists and then actually hold the specimen the describe taking - which is an amazing link back in history.

Evolution of the dataset

Fast speed forward to 1976. Between 1976 and around 2009 the data held by the HRS was primarily supplied by people who at least partially retained specimens. Over 50% of the data were supplied by around 20 people. Those people generally record all taxa - in other words they tackle difficult genera such as Cheilosia and Pipiza. Having voucher specimens is essential if there are questions about a species' identity or if there is a split. Even experienced recorders make mistakes and being able to check is helpful. Only yesterday I spent the afternoon checking the IDs of specimens forwarded for verification. Not all were right, even from very experienced recorders. So, we must assume there are dodgy records in the dataset (some mine I expect).

The degree to which records are dodgy is often difficult to tell, but I have four species in mind where I think the maps definitely include significant misinformation: Lejogaster tarsata, Platycheirus immarginatus, P. nielseni and possibly Eristalinus aeneus. In the case of the Platycheirus I think we will have to restrict maps to cases where males have been recorded - females are too readily confused with others. This means that we will only get a realistic picture from specimens.

That leaves another 50% of data. What I have found is that there is a strong separation between the records of the nucleus who retain specimens and the remainder of the data, with far fewer records of tricky species/genera, and far more of species that can to a greater or lesser degree be identified from photographs or in the wild. Of course, we do get small blocks of data from people who work all taxa but do relatively little recording, so the data are not simply dominated by recorders who don't tackle tricky species. These data exclude lists where I take one look and say 'Chinnery' - there are ways of telling how recorders behave and the sources they use. They also exclude lists where it seems to me that the author has not used the key or bothered to check on a species' distribution - the presence of Scottish or coastal species in a list for a dry southern grassland is a fair indication!

So, moving on to the era where the mantra is: take nothing but photos and leave nothing but footprints. I am just finalising an analysis of species covered by photographs over 2014. That highlights just over 130 species (I have excluded a few photos of rare animals that were posted because I know they will arrive via lists supplied by the author). I also have an analysis of what has not been identified - no great surprises - dominated by Cheilosia, Pipiza, Platycheirus, but also including lots of Syrphus and Eristalis. So, bearing in mind this dataset comprises over 10,000 records (all records extracted from internet sources in 2014), there is a new influence on the dataset that will have to be taken into account when data are analysed for trends.

Based on past analysis of photographic records, I reckon that maybe 150 species will be recorded in this way, but that no more than 10 species will dominate the data, and no more than 35-40 will occur in sufficient numbers to perform any year-on-year analysis. Whether numbers will be sufficiently big to undertake latitudinal analysis remains to be seen, but I suspect the list will be depleted further.

Should specimens be retained?

We therefore hit the point where one must ask the question 'is it necessary to retain specimens?' If one wants to understand what is going on in the natural environment there is a need for quantitative data. In broad terms, that means trapping (and killing). But, trapping is fairly indiscriminate and does not necessarily cover all taxa. Also, trapping can kill large numbers of 'rare' species before this is detected. In the case of poorly known taxa this may never be detected. So, although trapping has its place, it has many drawbacks. If trapping is used to sample a narrow spectrum of animals then what happens to the by-catch? Bearing in mind this can be voluminous, the chances of it being tackled by a specialist are small. BUT, the data are quantitative and can probably be repeated at suitable intervals, thus forming a long time-series. One of the best examples of this is the Rothampstead moth survey. Jenny Owen's malaise trap also produced a really valuable time-series from her Leicester garden. These are rare, but valuable resources, and anything Government funded is under threat, so may not be available in future.

The Rothampstead programme has already been cut. Its loss would be catastrophic because it has highlighted a terrible decline in moth populations. Those changes are not down to retaining specimens - they are a mixture of climatic factors and anthropogenic changes to the countryside. Similar declines can be detect for many other taxa, including hoverflies. About 40% of our hoverfly fauna is in decline. We know this from the HRS dataset, which is supplied by a mixture of lethal and non-lethal sources, collected largely in an ad-hoc manner. These data are not ideal, but they are the best we have.

So, we now return to the question of retaining specimens in this modern World. A relatively small number of people retain specimens and many of them contribute extensive lists to the HRS. My guess is that around 150 people across Britain retain any level of specimens, and most retain very little. The contribution they make to the dataset is considerable, however. Perhaps not every specimen needs to be retained, but overall the impact of specimen retention is negligible. Conversely, the impact of the contribution to the dataset is considerable. Like it or not, we actually need people who are prepared to retain specimens and are driven by this interest. If we rely on non-lethal techniques then we will see a diminution in the value of the dataset.

It is therefore important to put specimen retention into context. Anybody who has watched social wasps hunting will know that they are voracious killers. A single nest may kill many tens of thousands of insects. Stuart and I did a bit of work in a small wood in Northamptonshire a few years ago that showed there was a strong probability of about 1 wasp's nest for every 1.5 ha of woodland. (i.e. around 40 nests in 60ha). That mounts up to a huge volume of invertebrate biomass. So social wasps are clearly important regulators of invertebrates. They happily munch hoverflies and if they have the same abilities of Anthrenus (museum beetle) my bet is that they take rare species disproportionately. So, our active Dipterist, working over the year, probably equates in impact to little more than a few workers within a social wasp nest, spread over a much larger area.

Ah, I hear you say, but if the 'collector' did not collect, then there would be more insects. TRUE! FRACTIONALLY! But also there would be CONSIDERABLY less data.

A further moral dilemma

So let us move on to the take nothing but footprints argument. No hoverflies were killed in the making of this day out? Well, maybe. But if you drive to your venue that may not be so. We know that huge volumes of insects are killed in collision with cars. So, those who choose not to take specimens but enjoy watching wildlife in special places are also taking an informed decision to kill. It is just that they do so indiscriminately and with little knowledge of what they are doing.

I have had this debate with several proponents of this philosophy and am amazed by the answers they give - very largely about the fact that this improves their quality of life and the death of the insects they kill on the road is not intentional. How can this be? After all, they know that cars kill insects and will be irritated by the splat marks on the windscreen when they impair visibility. So, I fear, anybody who uses powered transport to conduct their hobby is having a negative impact on insects. Who knows if their victims are common or rare? The result is the same, but there is a difference between this approach and that of the entomologist who retains specimens. One generates partial data and the other more comprehensive data. Maybe this is a broad generalisation, but I think the key philosophical question relates to the contribution the deaths of insects make to our knowledge of insect ecology.

I therefore hold the view that the immoral issue is not about whether or not specimens are retained; it is about the degree to which we pursue our interests without making a contribution back to the wildlife we love. Detailed recording at whatever level can make a difference in highlighting the plight of wildlife. At least with robust data there is something to influence politicians and decision-makers. The biggest threat to wildlife is arguably the loss of taxonomically competent recorders whose contributions are essential if we are to track the trajectory of wildlife abundance.