Focusing on the familiar V: dragonflies part I

A few months ago, a reader suggested I took an occasional look at some more familiar species. As my chosen remit is to popularise and familiarise less well-known species, I mused for a bit and then thought 'OK, why not?' which led to a short series on ladybirds. Now I have a garden pond, created and filled just a few weeks ago, and already interesting species are starting to appear, something I've been nattering about on facebook quite a bit. So, it seemed a good time to have a close look at one species in a generally popular group - the dragonflies - in particular the Common Darter Sympetrum striolatum. In Britain, this is probably the most commonly seen smallish red dragonfly (not to be confused with damselflies which are much more spindly), and is one of a number of species in a genus known in North America as 'meadowhawks'.

Male common darter Sympetrum striolatum on water mint.

First of all, its range is huge - from Ireland, Iberia and parts of North Africa eastwards through Europe as far as Japan, with migrations seen which can be huge in number. Like other Sympetrum, only mature males are red and it is these which I will focus on here. Females and immature males are yellowish as is typical for this genus.

The abdomen is almost parallel-sided (just a weak constriction in the front half) unlike others such as the ruddy darter S. sanguineum which has a more distinctively 'club-like' appearance. The abdomen is an orangey rather than deep red, while the sides of the thorax also have clearly yellowish patches (visible in the photo below).

Male common darter Sympetrum striolatum on Buddleia davidii.

As dragonflies can be variable in terms of depth of colour and other abdominal features, it is sometimes necessary to look more closely at the head to separate species in this genus. In S. striolatum, there is a black area above the 'face' running between the eyes, but this does not extend down the inside edge of the eyes (as shown in the photo below), unlike in, for example, S. sanguineum and S. vulgatum (which although common in continental Europe, is only found in southern Britain as a scarce vagrant).

Head of male common darter Sympetrum sanguineum showing limited extent of black facial mark.

So, if you are in Britain and see a red dragonfly of this shape and colour, there's a good chance it will be a male S. striolatum, but do take care as there are other options, and more so if you are on the continent. If you would like to find out more about this and other British and European dragonfly species, I've included a reading list at the bottom of this page - and if you'd like more info about creating a wildlife-friendly garden pond, why not download an advice booklet here (from the excellent Pond Conservation). Enjoy!

Male common darter Sympetrum striolatum surveying our new pond from his perch on water mint

Birds in a box, beetles on pins

For those involved directly in taxonomy and species identification, the function of biological collections is well known e.g. to provide reference specimens, and more recently to create a potential source of genetic material for molecular research. For others, it may seem a somewhat outdated, even macabre, activity, but this is not the case as long as ethical guidelines are followed - such as a 'code of conduct for collecting' (there may also be legislation covering collecting that varies from country to country, so do beware and check for protected species and permit requirements). During my recent visit to the Oxford University Museum of Natural History (which I've heard referred to rather dismissively as 'the dead animal building'), I came across two excellent examples of why biological collections are of key importance in life science research. The first is an area you may have noticed me writing about quite a lot - small beetles; the second is quite different but more widely familiar, at least in broad terms.

A tray of scarabaeid beetles from the Hope Entomological Collections at the OUMNH

Trays of insects on cards and/or pins is one popular perception of a biological collection, along with stuffed animals, skeletons and 'pickled things in jars'. Although this is no some extent rue (visually at least), their purpose is not always well understood. For example, one reason for my recent visit to the OUMNH was to consult the Hope Entomological Collections. With over 5 million specimens this is the second most important such collection in the UK after that at the Natural History Museum in London. My reason for wanting to consult the collection was to help finish my key to identifying British Chrysomelidae, in particular the last few tricky species of Longitarsus flea beetles - L. curtus, L. fowleri and L. membranaceus. These are superficially very similar and I wanted to check some characteristics so that I could decide how to separate them in my book. They are also tricky because (a) I don't have my own beetle collection (I have nowhere to store one), (b) there is a very good collection maintained by the Hampshire Museums Service in Winchester; however although it is only 10km away, it tends to only be open when I am at work (an increasing problem in the UK as local government funding cuts reduce staffing and thus opening hours), and (c) these three species are not available as clear online photographs, even at the excellent European Chrysomelidae website. So, I went to Oxford to have a look at theirs - in particular fine details of the heads.

Longitarsus membranaceus

Longitarsus curtus

Longitarsus fowleri

I won't go into great morphological detail here, but the result is that I can now tell these three species apart from details of their heads - and so will anyone else be able to once my key is published - but in summary, L. membranaceus has a distinctive broad bar running down the front of its head, the sides of the bar being more or less parallel where it runs between the upper halves of the eyes, and it has a narrow process extending down between the antennal bases. In L. curtus, there is a broad wedge rather than a bar and this meets the upper edges of the eyes. In L. fowleri, the bar broadens towards the top of the head but is still separate from the eyes. So, with specimens and a microscope, a fairly straightforward way to separate some very similar species without needing to dissect them - and one that does not appear in existing keys, but could not have been determined without access to a collection. Plus, as I remembered to take my camera, there are now some useful photos that will appear when these species are Googled! Now, moving on to the second example, I enter the realm of an iconic vertebrate, the dodo (Raphus cucullatus).

The Oxford dodo display

This was not something I specifically went to visit, though it is an important exhibit, not just because the dodo is a popular metaphor for extinction, but because of the the information that can be gained by having the specimen in a biological collection. It is well known that the dodo was first discovered by Europeans on Mauritius in 1598 and that it was extinct by 1680 (though probably due more to pressure from other introduced animals rather than hunting by humans - apparently it wasn't very tasty!). However, despite being so iconic, little was known about its biology and ecology until recently. The best-known contemporary images are 17th and 18th century paintings but their portrayals of fat dodos are now known to be inaccurate, with research since the 1990s indicating a much slimmer bird even if precise estimates differ and work is ongoing (Kitchener, 1993a, b; Angst et al., 2011). The importance of the OUMNH's dodo specimen lies in the fact that it is the only specimen in the world with soft tissue preserved (skin on the head) from which DNA could be extracted. When this was analysed, the dodo, and its close relative the solitaire Pezophaps solitaria from the (relatively) nearby Rodrigues island, were found to be most closely related to the pigeons within the family Columbidae (Shapiro et al., 2002). This is a key result as the dodo had previously been taxonomically linked not just to pigeons, but also parrots, shorebirds and raptors - partly due to the lack of evidence/specimens and partly because of the considerable amount of adaptation and specialisation that occurred in its island location that rendered it superficially unlike any other bird, apart from the similarly poorly understood solitaire. The research indicates that the dodo and solitaire separated from south-east Asian relatives around 40 mya while able to fly, and dispersed to the Mascarene Islands. The dodo and solitaire then separated around 26 mya; Mauritous and Rodrigues are much younger (only around 8 and 1.5 my old respectively) which implies that the birds used the now-sunken Mascarene island chain as stepping stones, with the isolation of Rodrigues implying that the solitaire was able to fly as recently as 1.5 mya.

So, although genetics is only one area of research, and like any other needs to be applied and interpreted appropriately, this is an example where a modern technique and a traditional biological collection were both required for research purposes and combined to produce important results - the dodo is much more than a stuffed bird in a case, and genetics needs real-world applications beyond 'bar-coding' of species. It also highlights the point that when a specimen is collected, its use may be unknown as this specimens dates from long before the concept of the gene had been thought of. For an overview of some other applications of this technology, Nicholls (2005) covers some important points, and for much more detail about the 'Oxford dodo', have a look at this excellent OUMNH factsheet which I mercilessly plundered for background information.

References

Angst, D., Buffetaut, E. & Abourachid, A. (2011). The end of the fat dodo? A new mass estimate for Raphus cucullatus. Naturwissenschaften 98(3): 233-236.

Kitchener, A.C. (1993a). On the external appearance of the Dodo Raphus cucullatus (L.). Archives of Natural History 20(2): 279-301.

Kitchener, A.C. (1993b). Justice at last for the Dodo. New Scientist. (28.8.93)

Nicholls, H. (2005). Ancient DNA Comes of Age. Public Library of Science Biology 3(2): e56

Shapiro, B., Sibthorpe, D., Rambaut,A., Austin, J., Wragg, G.M., Bininda-Emonds, O.R.P., Lee, P.L.M. & Cooper, A. (2002). Flight of the Dodo. Science 295: 1683.

All the lonely beetles, where do they all come from?

Shortly before World War II, London’s Natural History Museum published the first edition of Common Insect Pests of Stored Food Products (Hinton & Corbet 1943), a slim volume providing a guide to the identification of such insects. Although not specifically covering beetles or non-native species, the topic is such that many of the species covered were indeed beetles, and that are number of these were introduced to Britain. However, it was not until the publication of Volume 1 of Insect Travellers (Aitken 1975) that the beetles recorded from cargoes imported into Britain were surveyed and presented comprehensively, whether or not they were seen as pest species. In Volume II (Aitken 1984), which covered insects other than beetles, the numbers, types and origins of cargoes were updated,  and extended to cover the period 1957 to 1977. The 1970s saw a shift from cargo stowage in ships’ holds towards the use of freight containers; in turn this led to the decline of ‘traditional’ ports with piecemeal unloading which allowed for easier inspection and application of insecticides. Therefore, ship and wharf inspection was virtually superceded by increased vigilance inland by the 1970s e.g. at the end points of cargo distribution such as factories, warehouses, mills and farms.

Fast-forwarding to 2010, a lot has changed. Britain now has a Non-native Species Secretariat (NNSS) with its associated Non-native Species Information Portal (NNSIP) of factsheets currently in development. In 2005, Natural England undertook an ‘Audit of Non-native Species in England’ which tabulated 2721 species and hybrids, of which 98 were beetles. Looking at these, the origins/native ranges can be approximately split as follows:

Europe 43

Australasia 16

North America 10

Asia (as a whole) 5

Eurasia 5

East Asia 3

South America 3

‘Tropics’ 3

Central America 2

Palaearctic 2

Africa 1

Europe & Africa 1

South Atlantic islands 1

Unknown 3

Although there is some doubt about the origins of some of these (e.g. a few listed under ‘Europe’ could turn out to be Eurasian), by far the most prevalent source of non-native beetle species is elsewhere in Europe, even though Asia, and especially China, is often cited anecdotally as such a source. It is true that many non-native plants originated in China, and that increased Chinese exports are likely to increase the transport of species from East Asia. However,  it should also be remembered that some Chinese beetles found in Britain and elsewhere are particularly striking such as the Asian longhorn beetle (Anoplophora glabripennis) and the citrus longhorn beetle (Anoplophora chinensis). These have in turn induced the production of many factsheets and column-inches about their invasiveness and damage to timber (e.g. Haack et al. 2010) and that the Internet allows much faster and broader familiarisation with such species than was the case when introductions were first being catalogued.

Asian longhorn beetle (Anoplophora glabripennis)

While other invertebrates may show a similar pattern (of 34 spiders on the NNSIP register, 20 are from Europe and none are strictly Asian), looking at new and potential invasive species as a whole (i.e. including all animal taxa) shows a different pattern. For example, since their 2005 audit, Natural England’s horizon-scanning (Parrott et al. 2009) highlights 63 species across its red ‘alert’, yellow ‘watch’, ‘black’ and ‘climate’ lists; of these, North America (13), East Asia (12) and Asia (9) are the key areas of origin with only 5 species originating elsewhere in Europe and 7 more widely in Eurasia.

There are many factors here, but some seem to stand out; 

• Beetles move by many means, often helped by humans, but many introductions into Britain are likely to be from Europe as their ranges expand northwards with climate change.
• Many terrestrial invertebrates, especially small species, can spread to new areas unaided – this is seen with ‘ballooning’ spiders.
• Larger species, particularly invertebrates are often spread intentionally such as fish species introduced for angling or ornamental purposes and subsequently escaping or being released.

So, to return to the title question ‘...where do they all come from?’, the answer is that they are from more-or-less everywhere, but often just across the English Channel – for those of us interested in species recording and finding new beasties, they are likely to keep us busy and there will no doubt be further striking exotics hitting the headlines as they appear in fruit shipments and imported houseplants. Meanwhile, the small and less obvious beetles will be making their quiet way from continental Europe...

References

Aitken, A.D. (1975). Insect Travellers. Volume I. Coleoptera. Technical Bulletin 31. Ministry of Agriculture, Fisheries and Food. HMSO, London.

Aitken, A.D. (1984). Insect Travellers, Volume II. MAFF Agricultural Development and Advisory Service Reference Book 437. HMSO, London.

Hinton, H.E. & Corbet, A.S. (1943). Common Insect Pests of Stored Food Products. British Museum (Natural History), London.

Haack, R., Hérard, F., Sun, J., & Turgeon, J. (2010). Managing invasive populations of Asian longhorned beetle and Citrus longhorned beetle: a wWorldwide perspective Annual Review of Entomology, 55 (1), 521-546 DOI: 10.1146/annurev-ento-112408-085427

Parrott, D., Roy, S., Baker, R., Cannon, R., Eyre, D., Hill, M., Wagner, M., Preston, C., Roy, H., Beckmann, B., Copp, G.H., Edmonds, N., Ellis, J., Laing, I., Britton, J.R., Gozlan, R.E. & Mumford, J. (2009). Horizon Scanning For New Invasive Non-native Animal Species in England. Natural England, Sheffield. (Natural England Contract No. SAE03-02-189, Natural England Commissioned Report NECR009).

Thank you to the US Fish & Wildlife Service for putting this image in the public domain. Much appreciated.

Playing with cars - can crows make their own roadkill?

It is well known that carrion crows (Corvus corone) frequently feed from roadkill. As they lack a bill specialised for tearing into flesh, they may need a carcass to be opened by another animal before being able to scavenge – a job done very effectively by the impact of a vehicle.

In Japan, they have been seen to use cars to crack walnuts, placing them on pedestrian crossings when the traffic stops, and after traffic has passed, waiting for the lights to change again in order to collect the opened nut safely; if the nuts are missed, they even hop down and shift them (see video here) (Nihei 1995). This is astonishing behaviour, first noted in Japan in 1990, but in hindsight not that difficult to imagine developing – after all, crows already drop prey items such as molluscs onto hard surfaces to break them. As well as being an area where research has been undertaken (Zach 1979), I have seen this on a stony beach in southern England, and a road is a hard surface. From this starting point – (1) drop hard food onto the road, (2) notice and remember that cars aid the food-opening process, (3) learn to avoid the dangerous cars, (4) notice that pedestrian crossings have safe traffic-free periods handily announced by lights and bleeping, (5) adapt points 1-4 by moving nuts if necessary. So, most impressive, but it still follows from development of a well-known behaviour in a new urban setting.

However, what about roadkill? I am not aware of crows dropping unopened carcasses onto roads (though suddenly it seems plausible if the carcass is small...), but on two occasions I have witnessed what looked, from my human perspective, like a crow ‘herding’ a pigeon into traffic... could it be creating its own roadkill? Speculative, yes, but also plausible I feel. Of course, it could simply be aggression with the crow pushing the pigeon roadwards by chance, but as the pigeon moved back towards the grass verge, the crow did appear to be trying to prevent it. I didn’t see the pigeon being run over on either occasion, but still I have to wonder and on both occasion I had a witness who agreed what the event looked like... Now, all that’s lacking is some evidence, so any similar observations would be really interesting and much appreciated, or of course indications that I’m talking scribble!

References

Nihei, Y. (1995). Variations of behaviour of Carrion Crows Corvus corone using automobiles as nutcrackers Japanese Journal of Ornithology, 44 (1), 21-35 DOI: 10.3838/jjo.44.21


Zach, R. (1979). Shell Dropping: Decision-making and optimal foraging in northwestern crows Behaviour, 68 (1), 106-117 DOI: 10.1163/156853979X00269