The marvels of chocolate

Have you ever wondered where chocolate comes from and if it is possible that there will be a chocolate shortage in the future? Have you ever wondered if chocolate has anything to do with entomology? According to the Telegraph newspaper the average person In the UK spends a minimum of £57 on chocolate per year. It is therefore no surprise that the Theobroma cacao tree, from which we get most of our chocolate, is the second most important tropical cash crop, being worth $5 billion, providing employment for approximately 40-50 million farmers in Africa and Asia. (Schawe et al. 2013). Chocolate is processed from cocoa beans which grow on the 5-8 metre tall T. cacao tree (Young, 1982). As well as chocolate the cocoa beans are also processed into many well-known products such as cocoa powder and cosmetics (Schawe et al. 2013). Chocolate is not only delicious, but it has actually played a major role in human society by representing power and celebration and was even historically used as a currency.

The red/ brown egg shaped cocoa pods containing the cocoa beans are only produced if the flower is successfully pollinated by a particular insect. For once we are not talking about bees. Although you probably will not believe me, the pollinator is actually a fly, well, two species of the biting midge. Their Latin names are Forcipomyia quasiingrami and Lasiohela nana and they both belong to the Ceratopogonidae family (Young,1982). Can you believe it! Chocolate production is solely reliant on a biting midge!

The biting midge is 2-3mm long, about the size of a grain of rice (Young, 1982). Considering how important the midge is it lives quite a secretive life, the larvae (maggot) feed on dead organic matter and fungus and the adults require pollen and blood for egg production (Leston, 1970). The midge larvae click and jump so maybe that has made you rethink your opinion of maggots (Frimpong, 2009). Well when you think of flies you may automatically think of their larvae the maggot. I am writing this to show you wonder of chocolate, I certainly don’t want to put you off it. But without the midge larvae there would be no chocolate! Therefore if we destroy this annoying midge we would have no chocolate. Which would be worse?

So when you think of chocolate what do you imagine the flowers would be like? Well actually they are 5 pink sepals, holding 5 pouch like yellow petals. The petals conceal a ring of 5 staminodes, infertile stamens which enclose a central ring of 5 stamens covered in pollen. The flower’s ovaries are in the centre. The midges hover and weave around the aromatic flowers before crawling into the petal. The red nectar lines guide the midge towards the central narrow nectaries, where it feeds on nectar. The pollen from the previous flower visited is transferred to the ovary, fertilising the seed. When the midge crawls out of the flower it consumes some of the stamens pollen, but a large majority of pollen sticks to the midges long caudal hairs (Young, 1985). The midge then flies up to 6m away or is blown 100m-3km away from the flower, to another flower (Frimpong, 2009; Klein et al. 2008; Groneveld, 2010) and so it continues.

So far so good, but what if I was to tell you this midge is becoming rare, then what would you say? And what should we do about this? What if I was also to tell you that these midges also depend on rotting bananas and fungus growth on them for larvae growth (Leston, 1970) would you change your mind about fungus? The main reason for the midges decline appears to be loss of its microhabitat of dead leaves and discarded cocoa pods. The farmers are keeping their plantations too clean, banana peel may be the answer.

There is an additional problem. This particular tree (T. cacao ) is inefficient at producing fruit. Flowers must be pollinated on their first day of bloom. Otherwise, after 2 days, the flowers drop to the ground. As a result less than 5% of the 10% of flowers that are successfully pollinated develop into fruit (Groneveld, 2010). So next time you open a 100g chocolate bar remember it took 1 pod with 30-40 seeds to produce it. In a year alone the cocoa industry uses about 35 trillion cocoa pods. And so perhaps it is no wonder chocolate can be loosely translated to “the food of the gods”. So, next when you hear someone talking about the importance of bees just stop for a minute and consider the midges and how without them there would be no chocolate. And, next time a midge bites you think of their cousins the insect pollinators.

By Ruth Carter


References

Encyclopedia of Life. 2015. Theobroma cacao. [On-line]. Encyclopedia of Life. Available from: http://eol.org/pages/484592/overview [01/11/2015].

Frimponga, E., Gordona, I., Kwaponga, P. and Gemmill-Herrena, B. 2009. Dynamics of cocoa pollination: Tools and applications for surveying and monitoring cocoa pollinators. International Journal of Tropical Insect Science, 29 (2), pp. 62-69.

Groeneveld, J., Tscharntke, T., Moser, G. and Clough, Y. 2010. Experimental evidence for stronger cacao yield limitation by pollination than by plant resources. Perspectives in Plant Ecology, Evolution and Systematics, 12 pp. 183-191.

Kew. 2015. Theobroma cacao (cocoa tree). [On-line]. Home Science & Conservation, Discover plants and fungi. Available from: http://www.kew.org/science-conservation/plants-fungi/theobroma-cacao-cocoa-tree[01/11/2015].

Klein, A., Cunningham, S., Bos, M. and , S., I. 2008. Advances in pollination ecology from tropical plantation crops. Ecological Society of America, 89 (4), pp. 935-943.

Schawe, C., Durka, W., Tscharntke, T., Hensen, I. and Kessler, M. 2013. Gene flow and genetic diversity in cultivated and wild cacao (Theobroma cacao) in Bolivia1. American Journal of Botany, 100 (11), pp. 2271-2279.

Young, A. 1985. Studies of cecidomyiid midges (Diptera: Cecidomyiidae) as cocoa pollinators (Theobroma cacao L.) in Central America. Proceedings of the Entomological Society of Washington, 87 (1), pp. 49-79.

Young, A. 1982. Effects of shade cover and availability of midge breeding sites on pollinating midge populations and fruit set in two cocoa farms. Journal of Applied Ecology, 19 (1), pp. 47-63.

Young, A., Severson D. 1994. Comparative analysis of steam distilled floral oils of cacao cultivars (Theobroma cacao L., sterculiaceae) and attraction of flying insects: Implications for a Theobroma pollination syndrome. Journal of Chemical Ecology, 20 (10), pp. 2687-2703.

 

 

 

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What’s the point of wasps?

‘But seriously, what is the point of wasps?’ This is a question I often find myself being asked. Unlike their cute, somewhat fluffy cousins, the bees, it seems people have a much harder time accepting wasps. Indeed, they often find themselves on the wrong end of extreme prejudice with people willing to swat them without hesitation; there is even an ‘anti-wasp’ internet meme! This ‘speciesism’ should hardly be surprising given the emphasis placed on pollination services provided by the Apiformes. Wasps however, also play an important role in the functioning of our ecosystems; the health of which we rely upon for our very survival.

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Perhaps the single most important thing that wasps do for us is the provision of ecosystem services though pest control. Many species of social wasp are veracious generalist predators, with each nest capturing and removing many kilograms of arthropod prey from an ecosystem every year (Harris, 1996). Much of this removed biomass is that of species which would otherwise represent significant pests to our agricultural and forestry systems. Wasps can be so efficient at predating on arthropods that in some ecosystems where they have been introduced they actually represent a conservation concern by out-competing native insectivorous birds (Beggs, 2001).

Given this ability to help maintain the functioning of ecosystems, social wasps have occasionally been deliberately employed or encouraged as pest control agents. The introduction of nests has been used to provide successful biological control in production of cotton, tobacco, cabbage, coffee, fruit and timber (Spradbery, 1973). In fact, it is surprising how under-utilised they are considering their apparent ability to effectively control pests. Due to their generalist nature, in many ways social wasps are more highly suited for bio-control than some of some of the specialist species which are currently more widely used. For example, not only will they help maintain populations of multiple pest species below the levels that might affect yield, they are also able to maintain their own populations by utilising various other food sources. This means that their population is not tied to that of the pest species thus there is no ‘lag time’ between the initial outbreak and the time when there are sufficient numbers of predators to have a controlling effect. Furthermore, the social foraging behaviour of wasps causes them to return to sites with abundant food resources, meaning they will concentrate disproportionately at sites with highest pest densities, unlike other biological control agents which tend to distribute themselves more evenly (Richter, 2000). This will allow for more efficient control as the most damage occurs at the sites of greatest pest densities, which will be targeted first by the wasps.

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Contrary to what some people might believe, it is not just bees which pollinate! In fact, any insect which visits flowers has the potential to act as a pollinator. This includes beetles, butterflies, moths, flies and yes, even wasps. In fact, some plants, such as the Chiloglottis orchids, can only be pollinated by a single specific species of wasp (Peakall, 1990). Wasps normally pollinate during their search for carbohydrate rich nectar, but will occasionally frequent flowers during their search for prey. Sometimes they are even tricked into visiting flowers in reaction to volatiles released by the plant! Some species have evolved the ability to produce chemicals to attract male wasps by mimicking female sex pheromones (Schiestl et al., 2003) or by releasing damage signal volatiles to mimic pest damage to attract hunting wasps (Brodmann et al., 2008).

Wasps also have much to teach us. It was by watching wasps create their nests by mulching wood that Cai Lun, an official of the Chinese court of the Han Dynasty, first developed the idea of paper around 105AD. This now ubiquitous technology underlies much of the functioning of our society and owes its inspiration to the remarkable wasps. Even today we are learning much about social evolution by examining the range of socialities exhibited by wasps along with the underlying genomics.

By examination of the services that an organism provides us, it may become easier to justify why we should respect and safeguard them. This carries with it however, the danger that we should only value an organism by what it contributes to ourselves. This narcissistic view is dangerous as in reality human-kind knows very little about the complex world we inhabit. Surely species have a right to exist that is not solely determined by their detectable utility to one other particular species? Even if wasps did not provide us with all of these fantastic services free of charge, I would argue that they are beautiful creatures in their own way. Each individual organism we see around us represents the culmination of millions of years of evolution. Surely it should be a pleasure to share the planet with these creatures. This, I would argue, is ‘the point of wasps’.

By Liam Crowley.

References:

Ballou, H.A., 1913. Report on the prevalence of some pests and diseases in the West Indies during 1912. Barbados, West Indies, Bull. 13, pp.333-357.

Beggs, J., 2001. The ecological consequences of social wasps (Vespula spp.) invading an ecosystem that has an abundant carbohydrate resource. Biological Conservation, 99(1), pp.17-28.

Brodmann, J., Twele, R., Francke, W., Hölzler, G., Zhang, Q.H. and Ayasse, M., 2008. Orchids mimic green-leaf volatiles to attract prey-hunting wasps for pollination. Current Biology, 18(10), pp.740-744.

Harris, R.J., 1996. Frequency of overwintered Vespula germanica (Hymenoptera: Vespidae) colonies in scrubland‐pasture habitat and their impact on prey. New Zealand journal of zoology, 23(1), pp.11-17.

Peakall, R., 1990. Responses of male Zaspilothynnus trilobatus Turner wasps to females and the sexually deceptive orchid it pollinates. Functional Ecology, pp.159-167.

Richter, M.R., 2000. Social wasp (Hymenoptera: Vespidae) foraging behaviour. Annual review of entomology, 45(1), p.142.

Schiestl, F.P., Peakall, R., Mant, J.G., Ibarra, F., Schulz, C., Franke, S. and Francke, W., 2003. The chemistry of sexual deception in an orchid-wasp pollination system. Science, 302(5644), pp.437-438.

Spradbery, J.P., 1973. Wasps. An account of the biology and natural history of social and solitary wasps, with particular reference to those of the British Isles. London: Sidgwick and Jackson Limited, pp.282-283.

Taxonomy bytes back: are insect avatars the solution to tackle the classification bottleneck?

We have been naming and describing the natural world around us for millennia, but how does this age-old science relate to the 21st century? Computers have revolutionised the modern world and smart phones have lead to global connectivity. Ideas shared, data accessed and unity of knowledge achieved at the tap of the finger. With growing interest in biodiversity and conservation many technological advances are assisting within these fields. Despite racing against the deteriorating environment, new species are being discovered at a record rate. It seems therefore, that it has never been more important to put the right name to the right species and to do so quickly.

We are currently facing a classification bottleneck. This is an issue of time, money and accessibility, constraining upon sheer number of new specimens being collected. That is not to mention the number of synonyms and misidentified species that need some serious TLC. As ever, time is money and experts are scarce, so this really is a problem of exponential proportion.

 

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Author with her own collection submitted for our Entomology MSc Diversity and Evolution of Insects module

The latest revolution sits in the hands of digitalisation, of avatars and of so called 3D cybertypes. The new age of taxonomy is well and truly upon us. Focal stacking software amalgamates a series of two dimensional images to create an otherwise impossible focal range, whilst visual-hull algorithms carve into three dimensional space, stitching these stacks into tangibility. A 3D replica, an avatar, is thrust into digital existence, with full natural colour and incredible intricacy. High resolution microtomography (microCT) can then be used as a non-invasive means to map internal morphology. The result: a high resolution colour, interactive 3D interface, with the ability to explore within, differentiating between systems.

These advancements have caused some stir. With rapid characterisation of species morphology and subsequent preservation in the digital domain there is scope for broad spectrum application within entomology and beyond. These visual aids can be complemented with quick access to distribution data, DNA barcodes, research on behaviour or whatever published data required. Just as existing tools can be accessed remotely by the global community, these avatars too are accessed online and utilised in a similar way. Data banks can be pooled and comprehensive catalogues of data created, eternalised online, accessible 24/7, all at the click of a button. Recent advancements in producing data miners to sift through academic journals online have already be noted for their potential in the field of medicine. One such data miner, launched by the Seattle-based institute AI2, is already in use. Currently capable of trawling computer science literature, developers aim to scale up the programme, with extension to medical, biological and other scientific disciplines.   Imagine the applications; to request a specimen from the collections and for it arrive instantaneously, perpetuated in digital perfection, to your desktop. It would contain with it a plethora of data, pooling prior research, amalgamating it to one dashboard. This is not to say that a digitalised avatar would replace the crucial type specimen. These new digital techniques are a means to acquire more data, to be more exhaustive and to enable greater ease of access, leading to higher efficiency within our field.

Our natural history collections represent centuries of passion, of exploration and of pioneers within their fields. More than just prestige, collections carry with them invaluable data, added to by centuries of continuing research. Taxonomy is not an archaic tradition, refined to dusty old cabinets behind the closed doors of museums. Taxonomy is as current today as it has ever been. It is time for taxonomy to once again hold its own, to invoke collaboration and inter-disciplinary interaction. Ultimately, we are working for the same cause. Let’s move into the digital age and grant accessibility to all. If knowledge is power and communication is key its time we join forces to liberate our knowledge in this time of rapid environmental change.

By Alice Mockford

 

References

Akkari, N., Enghoff, H. and Metscher, B.D. (2015). A New Dimension in Documenting New Species: High-Detail Imaging for Myriapod Taxonomy and First 3D Cybertype of a New Millipede Species (Diplopoda, Julida, Julidae). Plos One [Online] 10:e0135243. Available at: http://dx.plos.org/10.1371/journal.pone.0135243.

Erwin, T., Stoev, P., Georgiev, T. and Penev, L. (2015). ZooKeys 500 : traditions and innovations hand-in-hand servicing our taxonomic community. 8:1–8.

Godfray, H.C.J. (2002). Challenges for taxonomy. Nature 417:17–19.

Marshall S.A., Evenhuis N.L.   (2015) New species without dead bodies: a case for photo-based descriptions, illustrated by a striking new species of Marleyimyia Hesse (Diptera, Bombyliidae) from South Africa. ZooKeys 525: 117-127 (05 Oct 2015) doi: 10.3897/zookeys.525.6143

Nguyen, C., Lovell, D., Adcock, M. and La Salle, J. (2014). Capturing natural-colour 3D models of insects for species discovery and diagnostics. PLoS ONE 9:1–11.

Nguyen, C., Lovell, D., Oberprieler, R., Jennings, D., Adcock, M., Gates-Stuart, E. and La Salle, J. (2013). Virtual 3D models of insects for accelerated quarantine control. Proceedings of the IEEE International Conference on Computer Vision:161–167.

Qian, J., Lei, M., Dan, D., Yao, B., Zhou, X., Yang, Y., Yan, S., et al. (2015). Full-color structured illumination optical sectioning microscopy. Scientific Reports [Online] 5:14513. Available at: http://www.nature.com/doifinder/10.1038/srep14513.

La Salle, J., Wheeler, Q., Jackway, P., Winterton, S., Hobern, D. and Lovell, D. (2009). Accelerating taxonomic discovery through automated character extraction. Zootaxa 55:43–55.

Winterton, S.L., Guek, H.P. and Brooks, S.J. (2012). A charismatic new species of green lacewing discovered in Malaysia (Neuroptera, Chrysopidae): The confluence of citizen scientist, online image database and cybertaxonomy. ZooKeys 214:1–11.

 

Does Mother Always Know Best? – An Aphid’s Perspective

 

We all remember those teenage years, mum shouting from the doorway to get up and go to school, giving her tit bits of advice and usually finishing a sentence with ‘Don’t argue, I know what’s best for you!’ But what about insects, I’ve never read a study where they try to get their young out of bed early: so, do they know best?

If an insect could talk, would they say ‘thanks mum’? Probably not, more likely ‘who are you’ and have to go onto the Jeremy Kyle show to be told ‘You ARE the mother!’ So, what should a good reporter do? You guessed it, an interview. After hours of searching (okay, ten minutes – I couldn’t find my shoes), an aphid was found (a small pear shaped true bug with sucking mouthparts) 7 and she was not impressed with what I had to say!

After staring hard at her proboscis (wow, suddenly my nose seems very inadequate) we launched into it:

“Can you explain why you are a good mother?”

She huffed. “Honestly have you never read Craig and Ohgushi,2 well, it’s called the naïve adaptatonist hypothesis (something in the way she said naïve makes me think she was directing that right at me, seriously, I’m getting sass off a bug). She continued “It explains that mothers will pick the best site for oviposition (turns out this meant egg laying, I didn’t want to admit it at the time that she had a better vocabulary than me) and by having this plant preference the young laid on these sites have the best survival rates to adulthood.”3 She added breezily “There’s been loads of studies on it.”

“…I mean its easier when we eat the same food as our young, you eat until you want to lay and then just find a good place to do it, perfect. But some of my friends don’t stay here the full year round. They like to travel and have two host plants.3 My friend Mary spends the summer in a tree but each year she pops back to shrubs when she lays eggs to overwinter.”

I sit and think. So are they truly good parents, more importantly, are they better than us?

She continued – “There’s no swanky hospital for us insects, I have to make decisions, I mean, obviously one plant is going to be more nutritious, but what happens if there’s another plant that offers better protection from predators?!”1

“So what happens if you pick the wrong plant” I enquired, I mean how bad could it be?

“Slow growth mostly…”

“Well, that doesn’t sound so…”

“… OR death, from predators or we might not be able to feed from the right leaves.”

I’m feeling guilty; death seems a bit much for just laying your egg in the wrong place. But I’m a reporter and time to play my trump card.

“I’ve heard you just lay your eggs in places which are only beneficial to you.”6

“Where’d you hear that?” she replied.

I shrugged “It’s just a theory.”

“What about the theory that states we lay young elsewhere in order to increase their lifespan?”

Touché! I had to admit I had looked, there are lots of studies out there with conflicting evidence! Some argue larval survival is connected to the mother’s oviposition choice, 5 others have found a weak or no effect.3 How are you suppose to make sense of all this?

“Have you read the latest meta-analysis?”

“Meta-what-now?”

“Analysis, it’s a study which analyses the significance all written studies to see an overall effect, it’s fantastic, explains what I’ve been saying all along, we pick a site that best helps our young.”4

“What about the experiments that don’t work then?” Surely she couldn’t have an answer for everything!

She sighed. “Maybe when it didn’t work it was the research that had problems such as bad weather (though you should already be used to that), wrong plants so you had to make the best of a bad situation, too few insects involved or maybe these lab experiments are not as representative of the wild as you seem to think.”8

Well didn’t this just take a complex turn, I thought I had it all figured out. I don’t think I could make all these right choices, some days I can’t even find two socks that match.

“Nothing’s ever that simple, much to learn you still have, young writer” (wait, did she just quote star wars at me?) and then she was gone.

Turns out I’ve learnt lots, mums like to huff; they like to be right and as it turns out, they usually are, (but don’t tell mine that). So next time your mother gives you some advice, maybe you should listen to her; after all, mother knows best!

By Christina Faulder

References

  1. Björkman, C., Larsson, S. and Bommarco, R. 1997. Oviposition preferences in pine sawflies: a trade-off between larval growth and defence against natural enemies. Oikos, 79 (1), pp.45–52.
  2. Craig, T.P. and Ohgushi, T. 2002. Preference and performance are correlated in the spittlebug Aphrophora pectoralis on four species of willow. Ecological Entomology, 27 (5), pp.529-540.
  3. Friberg, M. and Wiklund, C. 2009. Host plant preference and performance of the sibling species of butterflies Leptidea sinapis and Leptidea Reali: a test of the trade-off hypothesis for food specialisation. Oecologia, 159 (1), pp.127-137.
  4. Gripenberg, S., Mayhew, P.J., Parnell, M. and Roslin, T. 2010. A meta-analysis of preference–performance relationships in phytophagous insects. Ecology Letters, 13 (3), pp.383-393.
  5. Ishiwara, M. and Ohgushi, T. 2008. Enemy-free space? Host preference and larval performance of a willow leaf beetle. Population Ecology, 50 (1), pp.35-43.
  6. Jervis, M.A., Ellers, J. and Harvey, J.A. 2008. Resource acquisition, allocation, and utilization in parasitoid reproductive strategies. Annual Review of Entomology, 53, pp. 361-385.
  7. Kindlmann, P. and Dixon, A.F.G. 2010. Modelling population dynamics of aphids and their natural enemies. In: Kindlmann, P., Dixon, A.F.G and Michaud, J.P. In. Aphid biodiversity under environmental change: patterns and processes. London: Springer Science & Business Media. pp.1-20.
  8. Mayhew, P.J. 2001. Herbivore host choice and optimal bad motherhood. Trends in Ecology & Evolution, 16 (4), pp.165-167.