Monthly Archives: December 2018

…at random

It’s coming up to Christmas so I thought I would be a bit of a Grinch 🙂  As someone who has refereed a lot of papers in my time, one of my particular bugbears is when I come across the phrases,  “taken at random”, “sampled randomly” or variations thereon. My edition of the OED defines at random as “haphazard without aim or purpose, or principle, heedlessly”; the statistical part of the definition qualifies this further as “equal chances for each item to be selected”.  Whenever I see the word random in the methods and materials section I annotate the paper with the phrase “truly random or haphazardly?”  Almost without exception*, when the author responds to my query, it is to admit that in reality they meant haphazardly.

There is a commonly held belief among field biologists that random sampling can be quickly and safely done by standing in a field and throwing a quadrat over their shoulder or closing their eyes and throwing the quadrat into the air. The late great Sir Richard Southwood  deals with this myth in his usual no nonsense style  “Biologists often use methods for random sampling that are less precise than the use of random numbers, such as throwing a stick or quadrat.  Such methods are not strictly random” (Southwood, 1966).  If you have ever tried this yourself, you will, I hope, be the first to admit, that you position yourself in all sorts of non-random ways, to make sure that the quadrat is not going to get lost, get hung-up in a tree, end up in a lake or river or miss the only green bit of vegetation in the field. Other so-called random approaches include the walking around the tree/into the meadow/along the path approach and examining the first leaf/branch/plant you come across after x number of steps and counting what you see on that. Again, this is equally subject to being confounded by the terrain and location of the site, and it is a rare person who isn’t subconsciously swayed for or against a leaf because of its appearance.  I was convinced that this mode of sampling, which is more accurately described as haphazard, was commonly called professorial random sampling.  A recent request by me on Twitter for people to tell me if they had heard of, or used the term themselves, resulted in a zero response rate, so perhaps it was just something we used in our lab. Of course, it wasn’t a random survey so I shouldn’t read too much into it 🙂

So, if you are going to claim that you sampled randomly or selected/arranged randomly, make sure you use a random number generator.  It is very simple to do, although somewhat time-consuming to implement in reality. When I was a student, most good statistics books included among all the other useful tables, a page of random numbers to help you meet a state of true randomness.

Pre-prepared random numbers from my copy of Sokal & Rohlf (1973)


Nowadays, you can, if you use Excel, generate random numbers using the function RAND. Those of you who are not fans of Excel can try this handy link

If you’re reading this, you now have no excuses left.  If you are going to claim that you did something randomly make sure you actually did so, or confess that you sampled haphazardly; it is nothing to be ashamed of 🙂 and is much faster than true random sampling, hence its popularity.  Alternatively, you can avoid the whole issue and sample along a stratified transect or arrange your experimental blocks using a Latin Square.



Sokal, R.R. & Rohlf, F.J. (1973) Introduction to Biostatistsics.  W.H. Freeman & Company, San Francisco.

Southwood, T.R.E. (1966) Ecological Methods.  Chapman & Hall, London.

*I have, on a few occasions, had an author respond that yes, they did indeed use random number tables and/or generators.



Filed under Bugbears, Science writing

Pick and Mix 25 – Natural History, Entomology & Ecology


Jeremy Fox asks “Did Darwin have a blind spot?”

Time to get more young people interested in taxonomy

On the same lines, an interview with Maya Leonard, author of the Beetle Boy trilogy and newly released Beetle Collector’s Handbook

Great to see someone starting a Natural History course at university level

Did you know that insects have had a huge influence on science fiction films?

Neither plant nor animal – a new branch on the tree of life?

Why museum collections are valuable and need preserving

More on the global decline in insect numbers and why we should be worried

A nice piece of research where the media headline is so wrong:  “Ants in Florida collect the skulls of other ants to decorate their nests” – see the actual paper here and make up your mind 🙂

How locust ecology inspired an opera


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Filed under Pick and mix

Not all aphids are extant – fossil aphids

Mention the word fossil and most people immediately think of dinosaurs, ammonites, early hominids and perhaps plants from the carboniferous.  For those of you who have coal-burning fires, have a look in your coal-scuttle, you may be surprised at what you find.  What most people don’t realise is that there are fossil insects and these include those fabulous insects, aphids 🙂

A beautifully preserved aphid, Mindarus harringtoni, named after, and owned by my friend, and fellow aphid enthusiast, Richard Harrington.

The oldest fossil of a true insect dates back to the Pragian (early Devonian) era (396-407 million years ago (Mya)) implying that they can, almost certainly, be dated back to the earlier Silurian period (434 Mya) (Engel & Grimaldi, 2004). Aphids, being relatively soft-bodied animals, tend to be less commonly found as stone fossils, but there are some fine examples in existence.  The oldest aphid fossil found so far is Vasegus triassicus from the Vosges area of France and dating back to 174-163 Mya (Szwedo & Nel, 2011).  I have a great admiration for taxonomists in general, but paleoentomologists really are worthy of worship, working as they do, with material, especially that found in rock deposits, of an extremely taxing nature.

Wing of the aphid Vosegus triassicus  (Szwedo & Nel, 2011)

A more recognisable aphid wing from the Lower Cretaceous (140 Mya).

Another contender for the oldest aphid was found in the Daohugou beds in China on the boundaries of the provinces of Inner Mongolia, Hebei and Liaoning (Huang et al., 2015).  These deposits have been dated back to about 165 Mya.  Given the inevitable distortion caused by the squashing, the fossils do look like some modern aphids and I am pretty certain that I can see the cauda which is one of the distinguishing characteristics of aphids.

Daopaphis magnalata with a visible cauda? (Huang et al., 2015)

Somewhat younger, a mere 15 000 000 years old, Palaeogreenidea rittae, which displays the other dead giveaway that tells you that you are looking at an aphid, the siphunculi.

Palaeogreenidea rittae, note the distinctive siphunculi.  Middle Miocene from Nevada (approximately 15 Mya) (Heie, 2006).

Amber, fossilised tree resin, is, however, where you are most likely to find ancient aphids.  Tree resin is a carbohydrate-based extremely sticky secretion of trees, particularly conifers. It is part of their defence system and is used to seal wounds and to trap and encapsulate any insect intent on forcing an entry into the heart of the tree. The majority of the insects found in resin have arrived there by accident; they have landed on it and found themselves trapped.  They gradually become engulfed by the resin and die a slow and lingering death, unless a bird plucks them from their sticky surroundings as a tasty snack.  Go into a pine forest or look at the resin bleeds that you often find on fruit trees and you will very soon find some hapless insect victims. Over time the resin hardens and becomes a substance known as copal.  This can then find its way into the soil; the tree falls over or the copal becomes detached and falls to the round. Once in the soil, the copal has the chance, over several million years, to harden further still and eventually become resin.  Any insect trapped in resin is perfectly preserved, ready for the intrepid palaeoentomologist to discover and name or entrepreneur to sell to curio collectors.

A very fine specimen with a very long stylet; presumably this fed on the trunk of trees.  Germaraphis spp. (Pemphigidae) 


A very recognisable aphid indeed, the antennal tubercles, siphunculi and cauda are all very clear.  Photo from Ross (2009).

Not all aphids in amber are as easy to identify as the two specimens above.  The example below is why I have such a great admiration for palaeoaphidologists.

I am told that this is an aphid.  Photographed and found by Gracie Price a placement student at Oxford University Museum of Natural History, reproduced with thanks to Darren Mann.

I have written earlier about the close relationships that many aphids have with ants and it seems from the number of times ants and aphids have been found in close proximity in amber inclusions, that this association has been in existence for at least 73 million years especially with Germaraphis dryoides (Heie, 1967; Perkovsky, 2009).

Ant and aphid in amber. It will cost you €100 if you want to own this specimen.

Another association, perhaps not so pleasant for the aphid, and also immortalised in amber, is that of a nematode parasite from 100 million years ago (Poinar, 2017).

Aphid in amber with nematode parasite (Poinar, 2017).

What can we learn from these amber inclusions?  First, by comparing them with modern aphids, we can make inferences about their life styles.  As Ole Heie (1967) pointed out, aphids with clawed tarsi (feet) and long mouth parts are almost certainly not only to be tree dwellers, but ones that fed through the bark on the stems or trunks.  Aphids that live on the underside of leaves need neither of these adaptations.  Are there any other inferences to be made? I have already pointed out that, the fossil evidence suggests the ant-aphid mutualism has been long-established.

Fossil aphids also allow us infer that as aphids are largely found in temperate zones, the climate in those sites where amber is easily found must also have been temperate when they were trapped by the then, fresh tree resin (Heie, 1967).  Palaeobiologists have attempted to reconstruct ancient ecosystems from fossils including insects.  A recent and innovative study comparing arthropods found in trapped in modern tree resins, sticky traps and Malaise traps with those in fossil amber suggests that amber inclusions reflect the insects closely associated with trees but not necessarily the overall community (Kraemer et al., 2018).  We can’t get DNA out of amber as suggested in Jurassic Park, but we can certainly get a lot of other biological information from this fantastic window into the past.

I’ll end on a cautionary note. Not all amber is real amber.  Fakes abound.  Plastic is often used as fake amber and is sold with insect inclusions or as jewellery.  An easy way to test if it is plastic or amber, is to see if it floats in a saturated salt solution, if it does it is probably amber. More difficult to detect, is fake amber that has been produced by melting down real amber or copal, and then had modern insects embedded in it while it is still liquid.  If your insect inclusion is very nicely and symmetrically arranged, then you can be sure it is a fake.  Not all such inclusions are sold as genuine, most openly advertise exactly what they are; I have several, gifts from families and students.

Modern insect embedded in plastic.



Engel, M.S. & Grimaldi, D. (2004) New light shed on the oldest insect. Nature, 427, 627-630.

Heie, O. (1967) Studies on Fossil Aphids (Homoptera: Aphidoidea) Especially in the Copenhagen Collection of Fossils in Baltic Amber. Spolia Zoologica Musei Hauniensis, Copenhagen.

Heie, O.E. (2006) Fossil aphids (Hemiptera: Sternorrhyncha) from Canadian Cretaceous amber and from the Miocene of Nevada. Insect Systematics & Evolution, 37, 91-104.

Huang, D., Wegierek, P., Żyła, D. & Nel, A. (2015) The oldest aphid of the family Oviparosiphidae (Hemiptera: Aphidoidea) from the Middle Jurassic of China. European Journal of Entomology, 112, 187-192.

Kraemer, M.M.S., Declos, X., Clapham, M.E., Arillo, A., Peris, D., Jäger, P., Sebner, F., Peñalver, E. (2018) Arthropods in modern resins reveal if amber accurately recorded forest arthropod communities. Proceedings of the National Academy of Sciences, USA, 115, 6739-6744

Perkovsky, E.E. (2009) On finding a single-clawed aphid, Germaraphis ungulata (Homoptera, Aphidinea), in a syniclusion with the ant Monomoroium mayrianum (Hymenoptera, Formicidae) in the Saxonian amber.  Paleontological Journal, 43, 1006-1007.

Poinar, G.O. (2017) A mermithid nematode, Cretacimermis aphidophilus sp. n. (Nematoda: Mermithidae) parasitizing an aphid (Hemiptera: Burmitaphididae) in Myanmar amber: a 100 million year association.  Nematology, 19, 509-513.

Ross, A. (2009) Amber – The Natural Time Capsule. NHM, London.

Szwedo, J. & Nel, A. (2011) The oldest aphid insect from the Middle Triassic of the Vosges, France. Acta Palaeontologica Polonica, 56, 757-766.


Filed under Aphids