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The Walking (Un)Dead: Zombie ants and the strange effects of parasitic fungi on ant behaviour​.

In the understorey of a tropical forest, a carpenter ant, of the species Camponotus leonardi, has descended from the canopy away from her regular foraging trails and staggers drunkenly along a branch. Her movements are jerky and conspicuous. She twitchily moves forwards and suddenly starts convulsing with such ferocity that she falls from the branch onto the ground before again taking up an erratic fitful path that zigzags and circles back on itself. Around noon, after several hours of climbing and aimless lurching (now no more than about twenty-five centimetres above the ground) the ant finds herself on the underside of a sapling leaf where, without warning, she forcefully sinks her mandibles into one of the leaf’s veins, gripping it firmly between her tightly locked jaws. Within six hours the ant is dead.  After two days, white hairs bristle from between her joints and a few days later these have become a brown mat covering the whole insect and a pinkish-white stalk has started to erupt from the base of the ant’s head. The stalk continues to grow and within two weeks it has reached twice the length of the ant’s body reaching towards the ground below.

This is a description of a “zombie-ant”, part of the life-cycle of a parasitic fungus, Ophiocordyceps unilateralis. This bizarre behaviour was first recorded by Alfred Russell Wallace in Sulawesi in 1859, but was not researched in much detail until quite recently. It has since been discovered that the fungus disrupts the normal behaviour of the ant through chemical interference in the brain, causing the infected ant to behave in ways that will improve the fungus’ opportunities to spread its spores and so reproduce. The fungus grows throughout the body cavity of the ant, using internal organs as food while the ant’s strong chitonous exoskeleton serves as a kind of capsule, protecting the fungus from drying out, being eaten, or further infection.

The earliest known record of a fungus visibly parasitizing an insect dates from about 105 million years ago, it is a male scale insect, preserved in amber, with two fungal stalks projecting from its head. But this fossil cannot tell us if the infected insect’s regular behaviour was changed or disrupted in any way.  Evidence of “Zombie-ant” behaviour dates from around 48 million years ago from fossilised leaves that show the distinct markings on either side of leaf veins left by the lock-jawed mandibles of Eocene epoch ants. This association is evidently ancient and seemingly very common, with about 1,000 species of fungal parasites of insects known to exist today. These fungal pathogens have evolved to become either strictly species-specific or more generalist in their target insects, with some able to infect hundreds of different species. The variety of fungal pathogens and potential hosts has created some peculiar behaviours in insects which have most likely co-evolved with the fungi.

It is sometimes difficult to know which of these insect behaviours are entirely involuntary and driven by the fungus to improve its own reproductive success; and which the insects have evolved as a form of defence against infection. One of these unresolved odd behaviours is when the ant host climbs to an elevated position in what is known as “summit disease”. This increases the area over which spores can spread through wind dispersal, and removes the ant from close proximity with its colony or relatives. It is unclear if this behaviour is a zombie state caused by the fungus or if it is an altruistic act of self-sacrifice by the ant. By moving to an area away from its relatives it might be saving the rest of the colony from the immediate spread of infection by what is sometimes called “adaptive suicide”.

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In this age-old struggle for survival the ants have developed adaptations to protect themselves and their nests from fungal infections. Grooming themselves and socially cleaning each other, allogrooming, they remove potentially harmful spores before these can penetrate the cuticle and take hold. Some ants spray poison in their nests to act as fungicides and if that fails to stop an infestation, they partition their nests by sealing off contaminated chambers. In some cases infected individuals are carried out of the nest by healthy workers; and as a last resort the entire colony relocates, abandoning the nest.

Zombie-like behaviour in insects is also caused by other types of parasites including bacteria and even other invertebrates. Such parasites are extreme versions of the multitudes of microscopic organisms that exist in and on all living things. This raises fascinating questions about the nature of any organism’s true independence in what are undoubtedly highly complex interrelated living systems. Zombie-ants provide us with a glimpse into this intricately tangled-web of molecular influences and behavioural adaptations – often leading us to wonder: who, ultimately, controls whom?

 

References:

  1. Andersen, S.B., Gerritsma, S., Yusah, K.M., Mayntz, D., Hywel-Jones, N.L., Billen, J., Boomsma, J.J. and Hughes, D.P. (2009) The Life of a Dead Ant: The Expression of an Adaptive Extended Phenotype. The American Naturalist, 174(3): 424-433.
  1. Hughes, D.P, Andersen, S.B., Hywel-Jones N.L., Himaman W., Billen, J. and Boomsma J.J. (2011) Behavioral Mechanisms and Morphological Symptoms of Zombie Ants Dying from Fungal Infection. BioMed Central: Ecology, 11(13).
  1. Pontoppidan M.-B., Himaman W., Hywel-Jones N.L., Boomsma J.J. and Hughes D.P. (2009) Graveyards on the Move: The Spatio-Temporal Distribution of Dead Ophiocordyceps-Infected Ants. Public Library of Science: ONE, 4(3): e4835.
  1. Shang, Y., Feng, P. and Wang, C. (2015) Fungi That Infect Insects: Altering Host Behaviour and Beyond. Public Library of Sciences: Pathogens, 11(8): e1005037
  1. Hughes, D.P., Wappler, T. and Labandeira C.C. (2010) Ancient death-grip leaf scars reveal ant–fungal parasitism. Biology Letters, 7: 67-70.
  1. Roy, H.E., Steinkraus, D.C., Eilenberg, J., Hajek, A.E. and Pell, J.K. (2006) Bizarre Interactions and Endgames: Entomopathogenic Fungi and Their Arthropod Hosts. Annual Review of Entomology, 51: 331-57
  1. Bekker, C. de, Quevillon, L.E., Smith, P.B., Fleming, K.R., Ghosh, D., Patterson, A.D. and Hughes, D.P. (2014) Species-Specific Ant Brain Manipulation by a Specialized Fungal Parasite. BioMed Central: Evolutionary Biology, 14(166).

All images ©Alex Wild http://www.alexanderwild.com

Faking it as a survival strategy

224139Cheats and Deceits: How animals and plants exploit and mislead. By Martin Stevens. Published by Oxford University Press (2016).

Last year, on a trip to Devon, I saw my first ever oil beetle (Meloe proscarabaeus). She was beautiful. Her black carapace glistened violet and blue in the sunlight. She was gravid and crawling along the footpath in search of a place to dig a nest burrow to lay her eggs. But what I did not yet appreciate was the extraordinary life cycle of these captivating beetles. The young of a related species, Meloe franciscanus, emerge from the nest and swarm up a nearby plant where they congregate in a mass mimicking the shape of a female solitary bee (Habropoda pallida) and release a chemical compound similar to the bee’s sexual pheromones.  This proves all too irresistible to male bees who are drawn to this aggregation and attempt to mate with it, presenting the larvae with the perfect opportunity to grab hold of the bee and clamber onto his back.  He then carries these passengers with him until he finds a female to mate with at which point the larvae instantly decamp onto the female. From here they then transfer to her nest where they devour the stored nectar, pollen and the bee’s eggs. The evolution of this complex mimicry is absolutely fascinating and forms part of Martin Stevens‘ interrogation of deception in Cheats and Deceits: How animals and plants exploit and mislead.

This book is an immensely informative and enjoyable exploration of the multiple roles deception plays in nature. Stevens sets out a detailed examination of a wide variety of instances of natural deception from well documented examples such as the evolution  of camouflage through industrial melanism in the Peppered Moth (Biston betularia) to current research into the resemblance to falling leaves in the movement and colouration of Draco cornutus, a gliding lizard from Borneo. It is to Stevens’ credit that this book makes for entertaining and effortless reading while clearly citing all the relevant research within context and pointing to areas where knowledge is still lacking.

The language of deception is important. Stevens takes the time to explain some of the more commonly used terms associated with deception such as camouflage (blending in to the environment), mimicry (assuming the appearance – be that visual, chemical, behavioural or acoustic – of another organism) and masquerade (taking the form of an inedible object – as with stick insects). Mimicry and masquerade therefore lead to misidentification while camouflage reduces detectability or impairs recognition. Mimicry also comes in various guises some of which can be described as: aggressive, when predators mimic harmless species to enable prey capture; Batesian, when a palatable species mimics the characters of an unpalatable species, as seen in the chicks of an Amazonian bird Laniocera hypopyrra mimicking toxic caterpillars; and imperfect mimicry, as with hoverflies roughly resembling certain species of wasps and bees (for which there are a number of competing theories).

This, of course, only scratches the surface of a vast area of research that Stevens specialises in as head of the Sensory Ecology and Evolution group at the University of Exeter where he continues to research these themes. His enthusiasm for his topic is highly infectious; you find yourself transported from an explanation of background matching in cuttlefish, to an historical aside concerning the development of military camouflage, and on again to a description of his own field experiments in testing the efficacy of disruptive colouration.

“We must trust to nothing but facts: these are presented to us by nature and cannot deceive. We ought, in every instance, to submit our reasoning to the test of experiment, and never to search for truth but by the natural road of experiment and observation.” ~ 18th-century chemist Antoine Lavoisier

The book does rely heavily on zoological examples, and although Stevens doesn’t entirely neglect plants his observations do tend to mainly focus on carnivorous plants and orchids. But to be fair, Stevens does make the point that more research into botanical forms of deception is required and suggests that this should be undertaken with a view to specifically exploring the roles of chemical signalling and sensory exploitation. One of the examples cited in the book is the orchid Epipactis veratrifolia which attracts female hoverflies to lay eggs on the plant by releasing chemicals that mimic the alarm pheromones of aphids (the food source of hoverfly larvae). This may rather be a means by which the orchid exploits an inbuilt perceptual preference for chemicals associated with hoverfly larval food sources – either way the plant is deceiving the insect in order to  ensure protection from aphid infestation.

A form of deception more commonly associated with orchids is that of exploiting male insects to pollinate plants by mimicking the female form through the shape and colouration of the flower. However, Stevens points out that this mimicry is sometimes (as in Cryptostylis orchids) not particularly convincing to human eyes, but is overwhelmingly so to the male wasp which tries to mate with the flower and thus collects the pollinium which will be deposited at the next Cryptostylis flower that he visits. With this example (as with the oil beetle, among others) the author cautions researchers of deception in nature to be aware of anthropocentric biases that may arise through our observations and study, and to (wherever possible) approach our subjects in the manner and with the senses of the deceived species.

I am utterly delighted and inspired by this book and am certain that I will return to it again and again as a point of reference. I have no hesitations in highly recommending it to researchers, field naturalists and those with a passing interest in natural history.

Postscript

At the time of writing, Phil Torres and Aaron Pomerantz have discovered and documented kleptoparasitism of ants in a species of butterfly (Adelotypa annulifera) in the Peruvian Amazon which they believe might mimic ants through their wing patterns. This seems to me an ideal opportunity for further research looking at visual and chemical mimicry given both the wing patterns and larval associations.

Getting down and dirty with the Earthworm Society of Britain

I attended the Earthworm Society of Britain‘s annual general meeting at Cannock Chase Forest where I got to meet fantastic amateur enthusiasts, very knowledgable naturalists with a general interest in worms, and some hardcore earthworm specialists. It was an immensely enjoyable couple of days of field recording in various habitats found here including broadleaved woodland, grassland and heath as well as microhabitats such as dead wood.

“It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures”. Charles Darwin

Since Darwin’s observations and experiments with earthworms was first published in 1881 under the title The Formation of Vegetable Mould, Through the Action of Worms, With Observations on Their Habits a new area of little-known research relating to these fascinating creatures was born. Despite this, we still find a lamentable lack of data regarding the distribution of earthworms throughout the UK and are continuing to research the ecosystem-wide implications of their below-ground activity.

In attending the society’s field day and AGM I was curious to find whether earthworms would pique my interest as a naturalist and scientist or whether I had developed a nostalgic yearning for simpler times. I have vivid memories of when, as a child, I would gingerly lift the edge of the damp burlap sack to scoop out trowel-fulls of fusty earth from half an oil drum in which my grandfather bred earthworms to bait his fishing hooks. I think the answer is that they are probably both true. This area is rich for contributions to research and recording while also being a great opportunity to get my hands stuck in some dirt and forget about my everyday worries. And when Amy Stewart so eloquently points out in response to the relevance of Darwin’s research and the significance of earthworms, that they’re “…only carrying out the natural order of things, folding the ruins of a farm, a city, or a society into the lower strata of the earth. When our civilizations end, and when we as individuals die, we don’t ascend, not physically. We descend. And the earth rises up to meet us”, how could I resist?

Day 1

Looking for earthworms is a messy affair and you have got to be prepared to get dirty. Armed with spades, sorting trays and all-weather gear we set out to see what the various sites had to offer.

ESBWe started with the damp, waterlogged woodland near  the classroom we had booked for the day and were immediately set upon by midges and mosquitoes. Ankle-deep in mud, and stippled with insect bites we dug 5 soil pits here with a reasonable haul of worms before making a break for an area of bracken further up the slope and farther away from the biting flies. We didn’t find any earthworms in the bracken pits, but were entertained by a greater spotted woodpecker feeding her voracious and loudly calling young in a nearby nesting hole before we again set off to a new site. A stop on the way to explore the banks of a stream and some adjacent dead wood in varying states of decay provided a few more worms for our count as well as other obligatory detritivores – millipedes, centipedes and woodlice.

It was in the pits dug from the grass verge alongside a footpath with flowering speedwell and buttercups  where the highest number of earthworms were found, along with leatherjackets and other unidentified fly and beetle larvae. Our small party of slightly bedraggled and filthy earthworm explorers then headed back to the Forestry Commission classroom. Looking to all the world like a group of unsuccessful treasure hunters or end-of-shift gravediggers we traipsed back to the promise of piping hot tea and freshly made sandwiches while a retinue of dog walkers, mountain bikers and Segway riders passed us by.  After lunch we could be found sitting in drifts of leaf litter in an old disused drainage ditch beneath a small stand of beech trees opposite the car park where we turned up a few more worms.

Then on to the AGM. First we were treated to a fascinating presentation on the worldwide diversity of earthworms (look out for the fried egg worm when in the Philippines) and an update on the ongoing search for the world’s longest earthworm (currently hotly contested between researchers in the Amazon and another in South Africa) by the society’s chair. Thereafter, the recording officer presented an assessment of the state of earthworm recording in the UK compared to other ‘more charismatic’ species such as butterflies – I think it’s fair to say that we have some way to go yet, but that significant progress has been made since the establishment of the society.  New members were elected to the committee (I am delighted to have been accepted as the new treasurer) and all matters were concluded and followed by dinner and drinks in a local pub.

Day 2

The next morning started with a sighting of a pair of Little Ringed Plovers on a derelict brownfield site near the hotel where we were staying before we bundled into cars and headed back to Cannock Chase with the intention of doing some mustard sampling,  digging soil pits in the heath and surveying areas that were being grazed by cattle. We set off on foot from the car park along the road until we reached a small wooded area with birch trees and much dead wood where we started collecting worms accompanied by the call of a cuckoo.

And then on to the next site where the shallow, stony and root-filled heathland pits that we eventually managed to dig were predictably uninhabited by earthworms; but we did manage to extract some from beneath some carpet tiles that had been scattered on a grassy area nearby using the diluted mustard concoction below (which I’ve been told is as indispensable as a spade to earthworm recorders).

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A little further down the path a rather large felled tree was rolled away to reveal more worms and a host of other creatures including a palmate newt, a toad,  an unidentified moth larva, pill millipedes, centipedes and  carabid beetles. We were also treated to a view of a tree pipit calling from the top of an oak and the slightly stumbling flight of a scorpion fly. We then made our way on to the grazed area where we wanted to do our final sampling for the day. Or we would have, but as we walked past the cinnabar moths and the many humped yellow meadow ant nests we realised that we may have misjudged the distance somewhat, so picked up the pace but didn’t get there with enough time to do any sampling. As a consolation we did spy a green tiger beetle scuttle across the chalk path as we now hastened back to the car park for a final catch up before scrubbing our hands clean and going our separate ways.

More information

You may have noticed that for a blog post on earthworms, this has been fairly light on any detailed earthworm records. This is because we don’t yet have our full set of records from those who attended the field days, and for my part as I am still a complete novice I am still working my way through the ID process. For ID resources, there is an excellent key by Emma Sherlock and an online  multi-access key developed by Richard Burkmar, both of which I highly recommend.

For a bit more information about earthworms and some of the work of the Earthworm Society watch this short youtube video produced by Eco Sapien and the FSC explaining why earthworms are important.
To get involved you can either contact the Earthworm Society directly or if you first want to try your hand at surveying earthworms you can take part in the citizen science project Earthworm Watch.

 

What is the cause of the Zika outbreak in the Americas?

I recently read an article by Claire Bernishthat said that the release of GM mosquitoes was the cause of the Zika virus outbreak in Brazil – this immediately set alarm bells ringing. As it turns out, any real evidence to support these claims was lacking and Christie Wilcox, writing for Discover magazine,has done a fantastic job in demolishing this argument by showing the inaccuracy of the dates and the distances involved. The GMM release site was 300 km away from the epicentre of the Zika outbreak and the release was in 2011-12, not 2015 as was stated in a similar article by Oliver Tickell in The Ecologist.3

 “The Earth is round, not flat (and it’s definitely not hollow). Last year was the hottest year on record, and climate change is really happening … And FFS, genetically modified mosquitoes didn’t start the Zika outbreak.” – Christie Wilcox 

Although I have my own concerns regarding the control of mosquitoes by means of genetic modification, I think that the scare-mongering surrounding GMMs and the Zika virus does more harm than good – especially when the scientific data is at best deficient and at worst entirely fabricated. Amongst the inevitable conspiracy theories that have surfaced the “best” argument that has been put forward seems to be that “Nature will find a way”. On another note, I also find the seeming disdain of laboratory scientists towards ecologists to be somewhat worrying and rather baffling. These fields have so much potential crossover that I hope any enmity can be set aside so that robust scientific research and enquiry can be conducted in a collaborative way.

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Aedes aegypti. Emil August Goeldi (1859-1917). Source: Wikimedia Commons.

This brings me to Amy Vittor’s excellent and comprehensive assessment of the potential sources of Zika in the Americas and her highly plausible proposition for why we are seeing such high infection rates.4 The Zika virus was first recorded in a rhesus monkey in the Zika forest in Uganda in 1947, then in the Aedes africanus mosquito the following year. The virus is now also found to be transmitted by Ae. albopictus and Ae. aegypti mosquitoes. These species are now found throughout the tropics and subtropics and as their ranges have expanded, so too has the possible reach of Zika and other mosquito-borne diseases associated with them. It wasn’t until 2007 that a large-scale outbreak of Zika infecting humans first occurred, infecting 75% of the population of the island of Yap in Micronesia.4, 5 

The spread of the virus is in all likelihood the result of human-aided dispersal of both the virus and Aedes mosquitoes. As the virus may not be detected by infected humans (up to 80% of infected people do not show any symptoms)4,5 and there is currently no cure, it is possible for an infected person to travel to an area where the virus has not been recorded and to spread it to previously unexposed mosquito populations there, so creating new vectors.

But what has changed to bring about this rapid spread of the disease in the Americas? If we accept that international travel by humans and the worldwide transportation of goods have enabled the means to transport the disease and its vectors, why are we only seeing these effects in the Americas now? There are a combination of further factors that have, as Vittor points out, come together to create the perfect environment for Zika to take hold and spread, including: the creation of more suitable mosquito habitat as a result of deforestation and planting arable crops or urbanisation; climate-change linked increases in temperature and/or humidity in areas that were previously too cold or dry to support mosquito populations; the failure of previous Aedes aegypti population control programmes; and the large pool of susceptible human hosts living in close proximity to each other and to these mosquito-favourable habitats.4

Mark Lynas, writing in The Guardian newspaper, also very effectively takes on the various GM mosquito conspiracy theories and then goes on to conclude that innocent lives will be lost if we do not embrace this technology.7 Although there is no doubt that mosquitoes are responsible for spreading an array of terrible diseases; the fact that we have created the conditions and opportunities for the mosquitoes and these diseases to extend beyond their historical ranges and infect many more people must surely be accepted as our own responsibility. I think it is a sad indictment of our scientists and ecologists if they cannot (or will not) work together towards an overarching framework to protect people from the effects of our own actions. We need to promote and encourage the use of ‘good science’ to inform our decisions and ultimately our actions.

Further research into and analysis of mosquito ecology is urgently required so that we can more fully understand the implications of mosquito eradication (by genetic or conventional controls) on the various associated ecosystems and diseases. If we do not ask questions about the potential impacts of our proposed actions, we are destined to repeat the same mistakes that have led us to this point. Perhaps, we should also examine the implications of increased habitat loss, climate change and urbanisation, and consider whether we are prepared to live with the consequences or take action to limit the most deleterious effects.

References:

1. Bernish, C. (2016) Zika Outbreak Epicenter in Same Area Where GM Mosquitoes Were Released in 2015 http://theantimedia.org/zika-outbreak-epicenter-in-same-area-where-gm-mosquitoes-were-released-in-2015/

2. Wilcox, C. (2016) No, GM Mosquitoes Didn’t Start The Zika Outbreak. http://blogs.discovermagazine.com/science-sushi/2016/01/31/genetically-modified-mosquitoes-didnt-start-zika-ourbreak/#.VrXcU8eExo4

3. Tickell, O. (2016) Pandora’s box: how GM mosquitos could have caused Brazil’s microcephaly disaster http://www.theecologist.org/News/news_analysis/2987024/pandoras_box_how_gm_mosquitos_could_have_caused_brazils_microcephaly_diasaster.html

4. Vittor, A. (2016) Explainer: where did Zika virus come from and why is it a problem in Brazil? https://theconversation.com/explainer-where-did-zika-virus-come-from-and-why-is-it-a-problem-in-brazil-53425

5. Duffy, R. et al. (2009) Zika virus outbreak on Yap Island, Federated States of Micronesia. New England Journal of Medicine. 360(24):2536-43 http://www.nejm.org/doi/full/10.1056/NEJMoa0805715#t=articleTop

6. Giri, D. (2016) Zika Virus : Structure, Epidemiology, Pathogenesis, Symptoms, Laboratory Diagnosis and Prevention http://laboratoryinfo.com/zika-virus-structure-epidemiology-pathogenesis-symptoms-laboratory-diagnosis-and-prevention/#sthash.BYXGYuyI.dpuf

7. Lynas, M. (2016) Alert! There’s a dangerous new viral outbreak: Zika conspiracy theories http://www.theguardian.com/world/2016/feb/04/alert-theres-a-dangerous-new-viral-outbreak-zika-conspiracy-theories

Further reading:

World Health Organisation (WHO) Latest Zika situation report http://www.who.int/emergencies/zika-virus/situation-report/en/

Genetically modified insects and the precautionary principle

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Last week the Guardian newspaper reported on the findings from the UK House of Lords’ science and technology committee into the development and use of GM insects. According to the committee’s chairman, Lord Selborne:

“GM insect technologies have the potential not only to save countless lives worldwide, but also to generate significant economic benefits for UK plc, where we are an acknowledged world leader.”

No surprises there. The case for GM insects to be developed as a form of vector control has many proponents and seizing an economic opportunity is to be expected from the Lords. Apart from a cursory explanation of the means of developing GM insects, and a mention of the fact that the committee would like to see a reform of European Union regulation around GMOs (more on this later), the reporter fails to consider any environmental issues that may arise from the release of transgenic insects, in what seems to me to be a failure of research and the rehashing of the committee’s summary report.

Thankfully, in an attempt to provide a balanced argument the Guardian also published a piece that was more critical of the report, describing it as  “an unsophisticated form of moral blackmail” and laying out the possible extinction risks associated with gene drive systems. The scientific knowledge gap is highlighted by these authors, who write:

“We are not against GM insects. Our point is that we do not know enough. Nobody knows enough.”

Though I commend these authors for responding to the Lords’report in a more critical way, there are still a couple of findings in the report that hadn’t been directly addressed and which I think need exploring further.

The first is the issue of EU regulations of GMOs that the Lords describe as “failing lamentably” and would like to see amended. This critique is aimed at EU Directive 2001/18/EC which states that “due attention be given to controlling risks from the deliberate release into the environment of genetically modified organisms”. This is to be conducted through case-by-case environmental risk assessments, public consultation, a requirement to consult all relevant scientific and ethical committees, and development of “a mechanism allowing the release of the GMOs to be modified, suspended or terminated where new information becomes available on the risks of such release” before consent will be granted. It is a very robust piece of legislation which, when linked with Regulation (EC) No 1946/2003 that restricts the release and transboundary movement of any GMO within EU member states, makes this not “lamentable” as the Lords would have us think, but sound legislation based on the Cartagena Protocol which states that products from new technologies must be based on the precautionary principle and allow nations to balance public health against economic benefits. And which allows countries to ban imports of a genetically modified organisms if they feel there is not enough scientific evidence that the product is safe. It seems to me that an attack on the governing EU legislation is also an attack on the Cartagena Protocol which environmentalists need to be aware of.

The international consensus of the definition of the Precautionary Principle is:

“When human activities may lead to morally unacceptable harm that is scientifically plausible but uncertain, actions shall be taken to avoid or diminish that harm.”

And this brings me to my second concern about the House of Lords report, wherein Professor Rosemary Hails states that:

“the Precautionary Principle properly applied would also take into account the risks of not developing a particular technology and the benefits forgone. It is a misuse of the Precautionary Principle that has led us to this place.”

This reconstitution of the Precautionary Principle is a matter of great concern and has already been discussed at some length by the House of Commons Science and Technology Committee in their Fifth Report: Advanced Genetic Techniques for Crop Improvement: Regulation, Risk and Precaution wherein Sir Mark Walport framed the precautionary principle not as a response to scientific uncertainty, but as a guide to evidence-based decision-making. He said:

“Decisions must be informed by the best evidence and expert advice. The application of the ‘precautionary principle’ can help to guide this. This simple idea just means working out and balancing in advance all the risks and benefits of action or inaction, and to make a proportionate response. All too often, people citing this principle simply overreact: if there is any potential hazard associated with an activity, then it should not be done, or, if it is already being done, it should be stopped.”

By removing the imperative for evidence and advice that is provided to governments to be based on the principles and rigour of scientific enquiry, the report is effectively providing ministers with a means of bypassing environmental legislation. A recent example of this is when George Eustice MP recently cited food security as a reason to maintain the use of neonicotinoid pesticides under this bastardised definition of the Precautionary Principle.

If it were as simple as Sir Mark maintains to identify and stop hazardous activities we would not be facing some of the world’s current health and environmental catastrophes. That is why we must legislate against them and that is why scientific evidence needs to be the basis for that legislation. And when that evidence is lacking or inconclusive, aren’t we safer not taking the risk in the first instance?  If, as Prof. Hails maintains we need to consider the risks of not using certain technologies for their potential benefits we have to ask ourselves whose benefits are we talking about.

The Great Pottery Throw Down

The title of this blogpost is taken from the latest BBC television series that has just finished screening in the UK. The premise for this series is based on the model developed for the hugely successful The Great British Bake Off, in which contestants compete against each other day-after-day to produce a variety of baked goods that are then judged by experts. Replace baked goods for ceramics and you will have grasped the intricacies of The Great Pottery Throw Down in its entirety. But what, if anything, is the significance of this to the study of invertebrates?

Well, having recently read Animal Architecture by Ingo Arndt and marvelled at the complexity and ingenuity of animals to create structures such as the heaped nests of wood ants, the towering cathedrals of termites and the delicately partitioned nests of paper wasps; I was rather taken with the notion of insects as ‘makers’. Serendipitously, I stumbled across the website of naturalist and artist, John Walters – specifically across his marvellous illustrations and accounts of Heath Potter Wasps, Eumenes coarctatus.

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Eumenes coarctatus. Source: Wikipedia

Potter wasps, Eumeninae, are the most diverse group of Vespidae, with over 3,500 species in 210 genera found throughout the world. Of these, 23 species in 9 genera are found in the UK. They derive their common name of potter (or mason) wasps from the fact that the females tend to construct nests from mud and clay. These nests can take multiple forms, but one of the most elegant (in my view) is the vase-shaped nest of Eumenes coarctatus, the solitary Heath Potter Wasp.

Using heather, gorse or dead grass stems as nesting sites, the female will build her clay vessel over the course of two to three hours. During this time she will repeatedly fly from a water source to a quarry site, where she will form a ball of mud in her jaws, which is then transported to the construction site where she builds the nest. Once she has shaped the neck and lip of the nest she lays a single egg in the chamber suspended on a strand of silk. She will then search for, sting and collect a number of small caterpillars, especially pug and horse chestnut moth larvae, from the heathland vegetation and then fills the pot with them. A final trip to the water source and quarry then provides enough clay to seal the pot with between 9 and 38 paralysed caterpillars trapped inside. A female heath potter wasp may produce up to 25 pots in her lifetime (2 to 3 months) and occasionally she will cluster pots as shown in the series of photographs below. It is possible that these clusters prefigure the development of eusocial colonies as seen in some other vespids.

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Development of a cluster of clay nest cells built by a single Eumenes coarctatus. Bovey Heath, Devon. Photos by John Walters.

When the wasp larva hatches from its suspended egg it drops onto the paralysed prey on which it feeds for about a week before pupating. The emergence of the adult depends on the timing of the building of the pot. If the pot was built before the end of June, the adult wasp will emerge 2 to 3 weeks later; if the pot is built in early July, the adult will still emerge in the same year; however, if the pot is built after this date emergence will be delayed until the following April or May.

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Illustration of Heath Potter Wasps taken from the field notes of artist and naturalist John Walters.

Though the E. coarctatus larvae are predatory, the adults feed on the nectar of heathland plants such as gorse, heather, bramble, angelica and alder buckthorn.

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Distribution map of Eumenes coarctatus in the UK. Source: NBN

Found on lowland heaths in England (from South Devon to East Sussex, and north to Buckinghamshire) the Heath Potter Wasp is classified as nationally scarce, though not designated a BAP species.

I also love Jean-Henri Fabre’s description of Eumenes taken from The Wonders of Instinct:

“A wasp-like garb of motley black and yellow; a slender and graceful figure; wings not spread out flat, when resting, but folded lengthwise in two; the abdomen a sort of chemist’s retort, which swells into a gourd and is fastened to the thorax by a long neck, first distending into a pear, then shrinking to a thread; a leisurely and silent flight; lonely habits.” 

More:

John Walters has also made a video of a wasp building a nest.

Michael Archer’s Key to British Potter and Mason Wasps is a very useful resource for identifying the various UK species.

The Little Bombardier

Best stay out of the way.

There are more than 500 species of Bombardier beetle (a form of ground beetle – Carbidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini all displaying the highly effective defence mechanism of releasing a superheated pulsing jet of noxious chemicals sprayed directly at would-be predators.  I have always been fascinated by the ammunition of Bombardier beetles – their highly accurate and violent chemical attack brought on whenever you touch them – but it was only on reading Eisner’s essay that I started to fully grasp the incredible complexity of these beetles.

These diagrams are reproduced from Thomas Eisner’s fascinating book For Love of Insects which explores the variety of ways in which insects use chemicals for defence, signalling and prey capture. I cannot recommend this book highly enough for anyone interested in the pursuit of entomology or study of chemical ecology.
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Diagram of a bombardier beetle with its 2 glands in place. R = reservoir; r.ch = reaction chamber; gl = glandular tissue; dt = duct

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The mechanism of operation of the bombardier glands. E = enzymes in the reaction chamber; R indicates that either a hydrogen (H) atom or a methyl group (CH3) can occur at that site on the hydroquinone or quinone molecule.

The chemical process involves hydrogen peroxide rapidly decomposing into oxygen and boiling water, while the hydroquinones oxidize into benzoquinone in the beetle’s reaction chambers. This mix explodes out of the beetle with an audible popping sound, in a volley of rapid-fire blasts – in a manner likened to the pulsing propulsion system of Germany’s V-1 “buzz bomb” in WWII. The consequent foul chemical burn (at 100°C) incapacitates smaller attackers like ants, and deters larger predators such as the unfortunate frogs in one of Eisner’s experiments.

By examining the propulsion mechanism using high-speed synchrotron X-ray imaging Eric Arndt from MIT confirmed Eisman and his colleagues’ qualitative passive ‘pulse jet’ model. This research shows that a flexible membrane and a valve passively control the spray pulsation – as pressure increases in the reaction chamber because of the chemical explosion, the membrane stretches and the valve closes. The membrane then relaxes and the valve reopens once the pressure has been reduced following the ejection of the liquid, and so the process repeats.

The only UK resident species of bombardiers are Brachinus sclopeta, the streaked bombardier beetle, and Brachinus crepitans, the common bombardier beetle, and both are rarely seen. B. sclopeta is so rare that it has only recently been accepted as a native species  (past records were  thought to be of rare migrants) and prior to 2005 had been presumed extinct since 1928. Because the beetles prefer habitats with thin soil, rubble and bare ground they tend to favour brownfield sites and have been found in east London; but with the continuous and unrelenting development of this area, these beetles’ futures are very precarious despite being listed as UK BAP priority species, and considered critically endangered by the IUCN. However, insect charity Buglife worked with developers to secure a site near London City Airport that is now the only known intact colony of the species in the UK. You can read Richard Jones highly informative blog about the relocation and conservation of this species.

Brachinus crepitans, though more common than B. sclopeta, is restricted to Southern England and Wales and especially the coastal areas of the South-East where it is considered nationally scarce. It is more commonly found in continental Europe, central Asia, the Middle East and North Africa, with central Sweden being the northernmost extreme of its range.

Brachinus crepitans. Image source: Wikipedia

Distribution of Brachinus crepitans. Source: NBN Gateway

Distribution of Brachinus crepitans. Source: NBN Gateway

Usually seen in May and June,  the beetle favours calcareous grasslands, arable field margins and chalk quarries. It is usually found in dry, sunny areas – typically under stones. Little is known about its life-cycle, but it is thought that the larvae are external parasites on the pupae of other species of beetle, particularly those of the ground beetle Amara convexiuscula and a staphylinid beetle, Ocypus ater. 

I think these gorgeous and enthralling beetles definitely warrant being surveyed for this coming Summer.


References:

  1. Eisner, T. (2003) For Love of Insects. Harvard University Press, Cambridge Ma.
  2. Lyneborg, L. (1976) Beetles in colour. Blandford Press, Dorset.
  3. Bombardier beetle found near Honeybourne. Worcestershire Biological Records Centre (December 2015): http://www.wbrc.org.uk/WorcRecd/Issue11/BombBtle.htm
  4. Isaak, M. 1997. Bombardier Beetles and the Argument of Design (December 2015):
    http://www.talkorigins.org/faqs/bombardier.html
  5. Streaked Bombardier Beetle. Buglife (December 2015) https://www.buglife.org.uk/campaigns-and-our-work/streaked-bombardier-beetle
  6. Brachinus sclopeta UK Priority Species Data Collation. Joint Nature Conservation Committee. http://jncc.defra.gov.uk/_speciespages/2093.pdf