Monday, 26 March 2018

Have honeybees obscured the real environmental pollinator dilemma?

A thread on the BWARS Facebook group yesterday brought the issue of honeybees on nature reserves sharply into focus. There seem to be two schools of thought (with permutations):

  • That the introduction of bee hives to nature reserves is a potential threat to natural pollinators as a result of inter-specific competition.
  • That the volumes of nectar available from particular nectar sources are so vast that there will be no effect on wild bees; and that natural pollinator numbers are so low that there is a need for bee hives to facilitate the necessary pollination services.

Needless to say, I sit in the first camp! But I only do so after careful thought (I am naturally quite pragmatic and aware of political sensitivities).

In past threads I have voiced concern about the potential for competition between honeybees and solitary/wild colonial bees. But, I have also been less than certain that there was detrimental competition between honeybees and other pollinators such as hoverflies.  My rationale was that whilst there is a direct link between pollen/nectar resources and wild bee brood success, other insects may not be as reliant upon nectar and pollen to ensure breeding success. Upon reflection, I think I may have under-estimated the importance of nectar to allow females to live as long as possible and to lay eggs in as many places as possible; and also the importance of pollen to facilitate egg maturation. Slap on the wrists for me! Nevertheless, there remains a dichotomy and it would be instructive to determine how vital nectar and pollen sources are to breeding success of individual species of flies (for example).

Yesterday’s thread brought my thinking far more into focus and I am now thoroughly convinced that on all counts there is no case for allowing honeybee hives to be placed on nature reserves. Unfortunately, as is also the case for wildfowling (where flight ponds sometimes ring wildfowl reserves), there is nothing to stop hives being placed in close proximity to nature reserves and for beekeepers to exploit the nectar and pollen resource that should be available for the natural pollinators.

A declining wild population

We know that wild pollinators have declined massively (across all taxa) but the reasons for decline are less certain. The chances are that there is no single factor (as I have written previously). Habitat loss and degradation are undoubtedly significant, as are the use of pesticides and herbicides. Others in the mix must also include atmospheric nitrification and climate change. We might also have to consider the impact of bee-borne pathogens spread by honeybees. Recent research suggests that pathogen levels in honeybees are pretty high, but are also high in some wild bees and have even been detected in some hoverflies.

There could easily be negative effects from honeybee farming. For example, I was amazed by the vast trucks of bee hives imported into the Lime woods of Serbia at flowering time. They must have stripped the trees bare of nectar! Yet, I have also seen/heard the same frenetic activity by bumblebees where honeybees were not dominant. One fantastic example was a Sycamore in Scotland that at 9pm literally hummed with bumblebee activity. I’ll bet a couple of beehives would put paid to that local population!

So, although there is scope for various avenues of research into inter-specific competition between hive bees and wild bees as well as other nectar and pollen-dependent taxa, there is a strong precautionary case for excluding bee hives both from nature reserves and from a zone around such reserves.

Cause for wider concern

I felt that the real worry about the honeybee debate was the suggestion that without honeybees wild plants on nature reserves would not get pollinated. This seems to me to be a spurious argument because honeybees make up just part of the range of pollinators. Furthermore, it is equally possible that honeybee numbers are suppressing productivity amongst wild pollinators and if the competition was removed then there would be scope for wild pollinator numbers to expand (assuming this competition is part of the problem). I would have thought it should be possible to investigate this interaction and the response of natural pollinators to reduction of competition.

The debate went further, with the implied suggestion that habitat creation would not be successful without pollinators, and that this by necessity was honeybees. Again, there is scope for research but the theory I would advance is that in the absence of honeybees there would be sufficient natural pollinators to facilitate plant development. Early successional stages should also mean that there would be bare ground, so beloved by solitary bees as nesting habitat. Aphid numbers are likely to be good amongst plants that do not require insect pollination (e.g. grasses) and as a result there should be plenty of hoverfly pollinators. It might take time for numbers to build up, but then that is what succession is about! Granted, some plants require long-tongued pollinators, but it is difficult to envisage a total absence of such insects in the timescales needed for habitat creation.

We know that replicates of natural grasslands can take many decades to acquire a representative flora, so there is time for the pollinator assemblage to evolve. Far more critically, where will the seeds come from and are the soil conditions right for specialist species? Soil chemistry, hydrology, bacteriology and mycology are probably far more critical factors underlying potential success of habitat creation schemes. Deep ploughing and herbicide/pesticide application have effectively destroyed most soils that might be used for habitat creation. In common with maintaining wildlife, nature reserves are critical natural soil assets.

So, if we want to safeguard pollinators per se, we must think about the impediments to their population growth. Honeybees have a place in the mix, but in a natural system there would be checks and balances on them too. It is therefore inappropriate to argue that because honeybees are a native species they should be the focus of attention to the detriment of wild species. I therefore think the research debate needs to shift towards the potential negative effects of importing honeybees into localised environments either on a permanent or temporary basis. In the meantime, the precautionary principle should apply because there are sufficient potential connections to construct a case for a detrimental effect.

Saturday, 17 March 2018

Choice of pinning system - direct pinning or staged mounts?

Not all insects can be identified in the field or from photographs; indeed, the majority probably cannot. There are, however, a few specialists who can do a fair bit in the field and from photographs. They can only do so because they have spent many years studying preserved specimens. Most observers of the natural world probably will not want to delve that deeply into species identification, but they may be keen to get specialists to do the identification for them. So, we definitely need specialists who have taken the trouble to develop the requisite skills. Newcomers will only manage this by taking specimens and making the necessary microscopic studies to hone their skills. Some advice on how to prepare and preserve specimens is therefore a necessary part of the mentoring process.

So, you have decided that you need to retain specimens in order to develop your technical skills. How do you set about it? For this session I will concentrate on the choice of pins for specimens that have been killed using your chosen medium (freezing, ethyl acetate, crushed laurel leaves).

Let us start with the critical issue. The ‘collection’ is not there to be an adornment – it is a working tool and the specimens need to be prepared so that they can be examined carefully from all angles. Equally importantly, the specimen is of no real value unless it is accompanied by relevant data – who collected it, the date on which it was taken, the locality name and a grid reference (in the UK using standard OS grid is probably best recognised). So, the specimen needs to have at least one, and possibly several labels. Once you have put an identity to it you will need at least a second label. So you need space on the pin.

For most Hymenoptera and flies, there are two main ways of pinning. Traditionally, a long pin has been used directly through the specimen. There are two lengths of pin that have been used – ‘English’ pins that are 30mm long, and ‘Continental’ pins that are 38mm long. Museums tend to favour Continental length pins because they have more space on which to place labels. However, many ‘collectors’ of old would use ‘English’ pins because they take up less space, require shallower boxes and are cheaper (standard lacemaking pins). I much prefer the longer continental pins because they also allow a lot more space for handling specimens without damaging the specimen.

Directly pinning using Continental pins carries with it the problem of storing lots of specimens whilst they dry and before they are fully labelled, but it does mean that you only have to write your data labels and place these on the pin. Many (but not all) Hymenopterists use this system.

There is the alternative that many Dipterists favour: short ‘micro’ pins made of stainless steel and produced in a variety of lengths and thicknesses from AA (the finest and most expensive) to E. For the most part pins graded A1 to A3, B1 to B3 and C1 to C3 are likely to suffice for the vast majority of Hymenoptera and Diptera in northern Europe. I tend to use a mixture of A1, B1 and B2 for all of my work (I never need to pin the larger animals as these are often doable in the field or I don't attempt them (e.g. bumblebees - if I cannot do it in the field I would not take a specimen - so I don't record many bumblebees).

If you work with micro-pins you have the advantage that you can store large numbers of specimens in a relatively confined space. Dipterists tend to use ‘Crystal Boxes’ – clear plastic boxes with a plastozote lining. These boxes are relatively pest-proof, can easily be stored and are a good way to keep specimens before staging and labelling (see Figure 1).
Figure 1. Micro-pinned specimens in cyrystal box. These include occasional beetles too, although pinning is probably not the way any serious Coleopterist would work! (I simply find it convenient)
The problem with micro-pins is that you then need to create a stage for the specimen on a longer pin (ideally a continental length pin). This is a fiddly and time-consuming job! But, staging does bring the advantage that the ‘stage’ acts as a bit of a shock-absorber (Figure 2). There are no conventions to the size of stage that you should use, nor to label size, but it is worth bearing in mind that the bigger the label and stage, the more space that will be required to store specimens – and that can get expensive! The other thing to bear in mind is that you will probably want to investigate both the upper and lower sides of your specimen, so big wide stages may impede your view of critical features; which is why I opt for narrow 3mm x 3mm stages of about 1.5cm long.
Figure 2. Staged and labelled Sciomyzidae - note two types of Continental pins used here - the expensive ones with nylon heads and the cheaper steel-headed pins bought because devaluation of the Pound has pushed the Austerlitz pins out of my price range!
The next and most important question is how to prepare labels? If you have nice neat hand writing you can of course do so using a permanent marker pen or Rotring pen. My eyesight and hand writing are too poor for this and I don’t have the time to write vast numbers of labels; so I generate them on the computer and print them onto thin card (ideally acid-free). Don’t use ink-jet printer unless you get permanent museum-grade ink. Other inks will fade and become illegible. A laser-printer is far more reliable and produces cleaner labels. I tend to go for labels in 6 point and using 0.7-line spaces. In so doing I can usually create labels approximately 1.5 cm by 1 cm. Remember that the labels need to be legible (at least under magnification) and they need to last if the specimen is to be of any long-term use.

Finally, it is important to remember that a 'collection' need not be a work of art! I tend te refer to specimens as 'a bit of chitin on a pin'. The real value of the collection is the science, so the specimens need to be accessible but not beautiful. I tend to side-pin pretty nearly everything with flies and have now started to side-pin some aculeates too (e.g. Pompilidae). Carefully spreading the wings may have no real value but may be aesthetically pleasing. But, it is important to be able to see relevant venation, so making sure critical features are exposed is essential. This can mean teasing out male genital capsules, ovipositors and possibly opening mouthparts (some bees). It is fiddly and time-consuming, and you often need to hold these structures in place whilst the specimen dries out - that is a definite advantage to micro-pinning!

Wednesday, 14 March 2018

Is it time to develop a ‘High Altitude Dipterists Group’?

I have felt for a long while that Dipterology in the UK was missing a trick because so few people do any field work at higher altitudes. David Horsfield and Iain McGowan have done a tremendous amount over the years, but they are the minority. Stuart ball and I have done a little bit – looking primarily for Gonathrus planiceps on Cairngorm, Glenshee and in the higher parts of the Pennines. In so-doing we have managed to find a few records of interest but in the course of many visits have only once found a single Gonarthrus! We believe that it is only found above 2,000 feet, so the numbers of potential locations are quite small outside Scotland. But, who goes high in England and Wales and makes a real effort to look for Diptera? 

Figure 1. Flush above Glenshee ski centre
The reality is that upland entomology is hard work and the range of species is quite small compared to a nice lowland woodland! Nevertheless, it is an important fauna and is one that is quite likely to be seriously affected by climate change. After all, our mountains are quite low and changes to the temperature profile could be dramatic. Some while ago, Stuart modelled the possible range of Cheilosia sahlbergi and predicted that it could be lost by the end of this Century! Those predictions come with a big ‘health warning’ but they highlight the possible plight of upland invertebrates.

Today, I was reminded further of how limited current recording is at higher altitudes. Martin Drake sent me maps of two montane Dolichpodids: Dolichopus maculipennis and Hydrophorus rufibarbis (Figures 2 & 3). They tell an obvious story of how poorly worked the uplands are! Although there are lots of old records there are frighteningly few modern ones. This deficit is almost certainly a lack of recorder effort.

Figure 2. Distribution of Dolichopus maculipennis as currently on the Dolichopodidae scheme dataset. The black dots represent most recent records.

Figure 3. Distribution of Hydrophorus rufibarbis as currently on the Dolichopodidae scheme dataset. The black dots represent most recent records.
Stuart and I have often discussed the idea of forming a ‘high altitude group’ to address this deficit. We are not as young and fit as we once were, but there ought to be lots of young entomologists just waiting for a challenge. I think in my 20s I could easily have been pushed into the mountains – especially if it had involved a bit of ropework and climbing. Most high altitude Dipterology simply requires a bit of strenuous exercise – so here is the challenge to the younger generation: how about looking high up for your Dipterological experience? The advantage is that the species range is quite small and there are lots of possibilities of short papers and articles on your findings – the literature is highly deficient.

In the meantime, I really ought to rise to the challenge of looking for upland Dolichopodidae and of course Platycheirus melanopsis and Cheilosia sahlbergi. The former was once known from the Lake District and I’ll bet it is still there! And what is there on the higher reaches of Snowdon, Tryfan and the higher peaks of North Wales?

Who said that all the low-hanging fruit had been picked? There is plenty to do looking at flush systems on different rock types and some nice ecology to be done. All it needs is a few energetic youngsters!