This blog article comes with a warning - for some reason my tolerance for what some may describe as revolting and distasteful seems to be very high. In fact I view those subjects that most people feel squeamish about as truly interesting - I think that nature is ingenious! So, in light of that forewarining, I will proceed…
I think that we are all aware that insects are great ... really great, attractive, adaptive, specialised little packages of wonder. And one thing that we should be ever so thankful for is that an awfully large number of them are decomposers. That is, they break down bodies ranging from large corpses to fallen leaves. And it’s not just the dead bodies that they break down - thankfully they remove waste too - so, think about a world without insects where we would be knee-high in faeces.
Many adult insects have developed novel ways to ensure that they are ready and waiting for fresh dung. Instead of locating freshly deposited material (I hope that you are not eating at the moment …), many species of beetle cling on to the ‘host’ and wait for them to defecate so that they can then fall off alongside their food. Check out the photo below with a family group (see doesn’t that sound cute!) of beetles clinging on to a monkey's nether region!
If you think this is extreme spare a thought for the poor dung beetle that hangs onto the backside of a kangaroo...
(Taken from Jacobs et al, 2008)
Sometimes insects take this life cycle a little too far even for me!
(From Encyclopedia of Entomology by John L. Capinera)
But let's get back to the main emphasis of the blog: flies and beetles are exceptionally valuable decomposers. The decomposing of animal and plant material is essential to ensure that there is a flow of nutrients round our ecosystems. When it’s not waste products, it's dead bodies. And that is what I want to concentrate on here today - what the flies do and how we can utilise this. Can you even begin to imagine what it would be like if there were not flies to break down the bodies of all shapes and sizes that would be littered around?
For the second episode of BBC Radio 4's Who's the Pest? I interviewed forensic entomologist Dr Martin Hall (aka Maggot Man), who works with me here at the Museum.
Maggot Man, Martin Hall, taking his work with flies very seriously!
He’s a brilliant man and he is not alone in working on insects (specifically flies) and their use in forensic entomology. In the department there used to be Maggot Boy - but sadly his postdoc has come to an end - and there is also Amoret Whittiker (not Maggot Girl!). Amoret has recently been the star of the Radio four program The Life Scientific and if you think that I have some strange quirks ... She has also been described thanks to her work on forensic entomology as a Superhero of Science - something to aim for!
The maggot is a common name for the larval stage of the fly and is generally associated with the more advanced flies, such as the houseflies and blow flies. In his fantastic books called the Natural History of Flies, Harold Oldroyd described maggots as precocious because they emerged earlier from the eggs in comparison to most insects, and are more plastic in terms of their structure. This feature has enabled maggots to get into and survive in an enourmous range of habitats.
The field that Martin and Amoret work in, amongst others, is that of forensics and this has become oh so popular since the advent of TV series such as CSI and Prime Suspect, but the use of insects to help determine the time of death is not a recent phenomenon. At the Museum we have a famous jar of maggots (not often I get to put that into a sentence) that was a sample from the first successful use of insects to tie a murderer to a victim! This story begins with Dr Buck Ruxton, who was a practising GP in Lancashire in the 1930's and was generally well-liked and respected within the community within which he lived and worked:
The rather dapper Dr Ruxton
Then, in September 1935, the bodies of his wife and maid turned up in small ravine miles away in Dumfriesshire, Scotland. He claimed that his maid had fallen pregnant and that his wife had run away with her to assist with an abortion so it couldn't have been him that killed them, guvnor. However, he was a sloppy man! Although their bodies were chopped up to make it more difficult to identify them, there were maggots still associated with the limbs and these were aged by Dr A.G. Mearns.
This provided a vital clue as to when the murders took place and it was this, coupled with the damning evidence that one of the newspapers used to wrap body parts was only found in Dr Ruxton's local region and not where the bodies were found, that led to the 'good' Doctor being found guilty and subsequently hanged.
So, you can see why they are precious maggots to us! For nearly 80 years we have been using insects as indicators of when and where death occurred to assist us in criminal proceedings in court, and we have long known about their effectiveness at turning up at the scenes of dastardly deeds.
In fact the ability to locate dead bodies is marvellous, and of primary importance are the flies from the family Calliphoridae, the blow flies. These include the common flies - the green bottles and the blue bottles - and many are very large and metallic-looking ... and arguably very attractive! These flies are always the first on the scene and they have an amazing ability to smell - they can detect a fresh corpse from up to 16 km away!
How can you not but admire this beautiful little creature? A Chrysomya megacephala male
Now, we know that these types of flies only lay their eggs on dead material so the maggots only develop after death (maggots living on live flesh is a whole different but interesting subject ... and really not for the faint-hearted). So, if we find maggots that are five days old, we can confidently say that the minimum postmortem interval (PMI) is five days - i.e. death could not have happened less than five days previously (it could be more, but it can't be less). However, under different conditions and differing temperatures, the development rate of the maggots varies and this is why we are still studying these species. And we know this because researchers have been working on the development rate of these flies for years and years.
Martin and Amoret have at times had decomposing material in the tower at the Museum (this has sometimes resulted, in the dead of winter, an enormous blue bottle winging its way down the stairs to come and say hello to the rest of us whilst we have our lunch; very friendly I thought). Up in the tower they are creating different ambient conditions to enable them to work out how this affects the developmental rate of the maggots and therefore more accurately determine time of death.
This idea is being used on a much grander scale in America where, in Tennessee amongst other places, there are facilities where people have donated their own bodies(!) after death to enable in-depth research into the decomposition processes. The Forensic Anthropology Centre, more colloquially known as the body farm is one such place.
The facility is located in an area of secluded woodland where there are many different experiments performed to look at the impact of different environmental factors on decomposition. Amoret herself conducted some experiments here to determine how comparable pig and human decomposition was (it is!) and I recently attended an entomology conference in Knoxville and listened to lectures from many forensic entomologists that either work there or utilise the knowledge that it generates.
So the fly that everyone goes 'ugh!' at is in fact an incredibly useful agent of the law in addition to its being a rubbish disposal unit and a 'keep the community tidy' advocate! Brilliant things - I have long been fascinated with maggots and their fantastic adaptability to penetrate so many different feeding niches!